Polymers doi: 10.3390/polym18141738

Authors: María Jordá-Reolid Ivan Dominguez-Candela Mirko Kunowsky Ignacio Sandoval-Pérez Asunción Martínez-García

There is a growing industrial interest in the development of functional plastic surfaces with hydrophobic and easy-to-clean properties, particularly in manufacturing sectors where safety, hygiene, and durability are critical requirements. This work investigates the development of hydrophobic and superhydrophobic surfaces on acrylic resin components fabricated by vat photopolymerisation (VPP), using a high-performance Rigid 10K photopolymer. The influence of manufacturing parameters, namely layer thickness and build orientation, on initial wettability was first evaluated, showing that orientation plays a more relevant role than layer thickness in controlling the water contact angle. Subsequently, different surface modification strategies were explored, including femtosecond laser microtexturing, sandblasting, and physical vapour deposition (PVD) coatings. Preliminary results indicate that femtosecond laser texturing enables controlled modification of surface roughness and wettability, with strong dependence on laser fluence and pitch. Sandblasting significantly increases surface roughness, promoting hydrophobic behaviour through the generation of irregular topographies. In contrast, PVD coatings appear to modify wettability primarily through surface chemistry. Roughness analysis suggests that, although layer thickness governs the initial surface condition, post-processing treatments progressively dominate the final surface morphology. Ongoing work is focused on fully correlating roughness parameters, surface morphology, and wettability performance. Overall, the combination of VPP and tailored surface treatments presents a promising approach for functionalising polymeric surfaces for advanced engineering applications.

Polymers doi: 10.3390/polym18141737

Authors: Bin Wang Zelin Li Fenglin Zhu Liangbo Yang Xingwen Zheng Shoulei Yan Ying Diao Zhongli Hu

This study focused on resistant starch (RS) from lotus, analyzing its content and structural characteristics across different lotus germplasms. Detection using the Dual-Wavelength Colorimetric Method revealed the following findings: The proportion of amylose in fresh lotus rhizomes was higher than that in fresh lotus seeds. The average content of resistant starch in fresh lotus rhizomes was also higher than that in fresh lotus seeds. After cooking, the resistant starch content of both lotus rhizomes and seeds decreased, with lotus seeds retaining a relatively higher amount of resistant starch post-cooking. Structural characterization showed that the surface of resistant starch from lotus seeds exhibited a grooved morphology, whereas that from lotus rhizomes appeared as irregular clusters. Additionally, the structure of raw resistant starch was more compact than that of cooked resistant starch. Fourier Transform Infrared (FTIR) Spectroscopy and X-ray diffraction (XRD) analyses confirmed that all lotus-derived resistant starches formed a type-C crystalline structure, with the crystallinity of resistant starch from lotus seeds being higher than that from lotus rhizomes. This study provides a theoretical foundation for breeding of high-RS lotus varieties and for the effective utilization of lotus germplasm. This work systematically compares RS composition and multi-scale structural differences between two edible lotus organs across a large germplasm population, clarifying the structural basis of RS variation, which distinguishes this study from previous single-material lotus RS research.

Polymers doi: 10.3390/polym18141736

Authors: Marina Gravit Vasily Prusakov Zybina Olga Muhammad Mudassar Chishti Irina Kotlyarskaya Maxim Sychov

Intumescent coatings are widely used to enhance the fire resistance of structural steel. In contrast to traditional fire protection methods, this novel flexible intumescent protection offers several key advantages: universal compatibility with other coatings (via non-contact wrapping), resistance to extreme temperatures (−60 °C to +90 °C), all-weather usability, and suitability for light-gauge cold-formed thin-walled steel structures. This paper describes the development and investigation of these fire-protective, flexible intumescent coatings based on eco-friendly binders (silicone polymers and acrylic resins) with varying intercalated graphite (IG) content from 0% to 40%. An IG content of 25–40% enables a steel I-section with a section factor of 294 mm−1 to reach its limit state at 44 min (compared to 15 min for unprotected steel). Fire tests on steel beams with a section factor of 172 mm−1 demonstrated that samples reached the deflection limit state at the 64th and 66th minutes, respectively. Thermogravimetric analysis (TGA) was used to determine the temperature ranges for the thermal decomposition and expansion of the IG. Mechanical property studies revealed the influence of IG on the elastic modulus and tensile strength. Accelerated climatic testing in moderately cold conditions and salt spray chamber tests confirmed that the intumescent roll coating has no negative impact on the steel substrates.

Polymers doi: 10.3390/polym18141735

Authors: Oana Grad Crina Socaci Mihaela Diana Lazar Adrian Pîrnău Anzar Khan

The cysteine-based thiol–epoxy ‘click’ reaction is demonstrated as an efficient and practical approach for the synthesis of zwitterionic structures. The transformation employs unprotected cysteine, proceeds in aqueous media, and affords quantitative conversions. Notably, acid- and base-catalyzed conditions provide exclusive access to different cysteine-based thioether regioisomers in aqueous conditions. The pH-responsive behavior of the resulting zwitterions is further elucidated by NMR spectroscopy. Finally, the synthetic strategy is extended to the preparation of cysteine- and glutathione-functionalized polyethylene glycol polymers, showcasing its utility for the preparation of amino acid-/peptide-containing macromolecular materials.

Polymers doi: 10.3390/polym18141734

Authors: Xiaoqing Feng Jiangwen Chen Lei Zhu Chao Cao Yunfei Cai Xin Luo

PETG/POE blends are thermo-responsive shape-memory systems with composition-dependent deformation and thermomechanical recovery behavior, but their molecular mechanism remains unclear. In this work, all-atom molecular dynamics simulations were performed for PETG/POE blends with different compositions. Model reliability was supported by density stabilization during equilibration and by reasonable agreement between simulated and experimental glass transition temperatures, with glass transition temperature deviations below 1.3%. Tensile simulations showed that increasing POE content reduced Young’s modulus from 1.81 to 1.10 GPa and yield stress from 0.251 to 0.144 GPa, indicating decreased stiffness and enhanced deformation accommodation. Free-volume and cavity analyses indicated tensile-induced packing loosening, cavity nucleation, and subsequent cavity growth and coalescence. Component-resolved interaction-energy decomposition and phase-resolved mean square displacement analyses showed strong PETG-related cohesive interactions, restricted PETG mobility at 200 K, enhanced POE mobility at 450 K, and relatively stronger PETG-POE interactions at intermediate compositions. These results help us to correlate blend composition, local structure, interaction-energy reorganization, chain conformation, and segmental mobility with fixation-recovery behavior. Under the present simulation protocol, PETG4/POE6 showed a relatively balanced response because of the compromise among rigidity, intermolecular interactions, cavity evolution, and thermally activated mobility.

Polymers doi: 10.3390/polym18141733

Authors: Koffi Enakoutsa Ivan Giorgio

Additive manufacturing has opened an extraordinary design space for polymer metamaterials, enabling microstructures whose macroscopic mechanical behavior is governed largely by geometry rather than by chemical composition. A principled design framework must solve two coupled problems: a forward problem (given a microstructure, predict effective properties) and an inverse problem (given target properties, generate a microstructure). Convolutional neural networks (CNNs) solve the forward problem accurately, but the inverse problem remains more challenging for three reasons reported in the literature: (i) many surrogates predict only a scalar proxy rather than the full second-order elastic tensor; (ii) fixed or randomly initialized inverse decoders create a distribution-shift gap between surrogate predictions and physical re-evaluation; and (iii) dataset bias toward near-solid configurations limits exploration of low-density and anisotropic designs. We present a unified framework, the Operator-Physics-Enhanced Reverse Architecture (OPERA), that addresses all three issues. First, the forward surrogate predicts the complete 3×3 plane-stress stiffness tensor Ceff in Voigt notation, with an analytical layer enforcing Cij=Cji and positive definiteness by construction, achieving R2>0.99 on the directional moduli and density and R2>0.88 on the off-diagonal coupling term C16 and the effective Poisson ratio. Second, a normalizing-flow decoder Fϕ, jointly trained with the forward surrogate, keeps inverse design on the training manifold and reduces the surrogate–PDE re-evaluation gap from more than 30% to below 6% on held-out targets. Third, a five-family dataset with uniform coverage of ρ∈[0.10,0.95] is augmented through an expected-improvement active-learning loop. We embed minimum-feature-size, connectivity, and print-direction constraints into the optimization through differentiable regularization and report agreement of R2=0.987 between predictions and tensile measurements on ten FDM-printed specimens. The framework is demonstrated on five problems (auxetic, extreme anisotropy, isotropic low-density, chiral, and hierarchical), with an average target error of 6.8%. The results are framed relative to a reproduced scalar-proxy baseline; we provide an explicit statistical uncertainty analysis, a baseline-reproduction protocol, and a discussion of the method’s assumptions and numerical enforcement.

Polymers doi: 10.3390/polym18141732

Authors: Yupeng Du Jinying Huang Zhenfang Fan Jiaolin Wei Wenwen Zhang Xiaolong Wang

The ride stability and driving comfort of vehicles are highly dependent on the performance of the damping system. The fatigue life prediction of damping components using rubber as the core damping material has become a research hotspot in the field of vehicle vibration isolation. Taking an automotive engine rubber isolator as the research carrier, this paper jointly carries out finite element simulation analysis and structural component fatigue life tests. A dual-parameter mapping framework is proposed, which integrates maximum strain energy density and cyclic energy dissipation instead of using a single damage indicator. This approach comprehensively accounts for the coupling effect of energy storage and energy dissipation coexisting under actual service conditions. Through uniaxial tensile tests on rubber specimens, combined with finite element simulations and physical model parameters, a quantitative mapping relationship between laboratory specimens and full-scale engine rubber isolators is established. Based on this mapping, the fatigue life curve of the isolator is derived from the specimen-based failure characteristics. Validation tests under two randomly selected operating conditions yield prediction errors of 7.5% and 6.9%, demonstrating that the proposed model can accurately achieve equivalent fatigue life transformation from small specimens to actual components. Unlike conventional direct extrapolation methods, this approach does not require complex multiaxial fatigue tests on the component itself; it only needs simple specimen fatigue data, significantly reducing development costs, while providing a reliable theoretical basis for material selection, fatigue performance optimization, and forward structural design of rubber isolators.

Polymers doi: 10.3390/polym18141731

Authors: Hasan Saygin Asli Baysal

Poly(lactic acid) (PLA) is widely recognized as a biodegradable bioplastic, yet reliance on industrial composting alone can forfeit embedded material and energy value when recovery is technically feasible. Recycling can retain this value, but PLA performance is affected by service-life aging, hydrolytic cleavage, thermal and shear history, and contamination. Whereas previous literature often treats end-of-life routes separately, this review integrates mechanical reprocessing, reactive upgrading, chemical and hydrothermal depolymerization, and life-cycle assessment within a feedstock–process–structure–performance–safety–circularity framework. We examine how molar mass, rheology, crystallinity, and mechanical performance evolve during recycling, and compare upgrading strategies, including chain extenders, plasticizers, blends, and fillers, in terms of property restoration, recyclability, migration, and ecotoxicity trade-offs. Chemical and hydrothermal routes are evaluated according to monomer yield, stereochemical purity, additive tolerance, repolymerization potential, and process severity. Life-cycle evidence shows that circularity cannot be defined solely by climate impact or biodegradability, as burden shifting may occur in terms of toxicity, energy demand, land use, and resource consumption. Accordingly, we propose a decision map linking feedstock quality with suitable routes and target applications. Overall, clean, dry, and traceable PLA should be prioritized for mechanical recycling, whereas degraded or contaminated streams require evidence-based upgrading or depolymerization instead of default disposal or composting practices.

Polymers doi: 10.3390/polym18141730

Authors: Néhémie Miloh Franck W. Boyom-Tatchemo Fabrice Nganbe-Ndjock Albert B. Mbouopda-Poupi Elie Acayanka Georges Kamgang-Youbi

To easily recover and reuse nano-magnetite (Fe3O4) during the catalytic process, Fe3O4 is successfully dispersed by coprecipitation of Fe(II, III) salts on anchoring sites of bagasse-sugarcane fibers generated by gliding-arc plasma. Previously, we explored the effect of ascorbic acid (ASC), hydrochloric acid (HCl) and plasma-activated water (PAW) acting as oxidation inhibitors of Fe(II) solution. Prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The obtained results show that the oxidation inhibitor agent influences the morphology, texture and activity of the synthesized bulk-magnetite, where Fe3O4-nanorods, Fe3O4-nanospheres and Fe3O4-nanosheets were, respectively, obtained with PAW, HCl and ASC. The Fenton-plasmacatalytic treatment of amaranth red dye used as a model pollutant for 30 min revealed degradation rates of 53, 79 and 80%, respectively, for Fe3O4-ASC, Fe3O4-HCl, and Fe3O4-PAW each coupled to plasma. The deposition of nano-magnetite on the plasma-activated bagasse-sugarcane fibers (BM) using PAW as the best oxidation inhibitor agent exhibited characteristic FTIR-absorption bands of -OH, -CH2 and Fe-O, attesting the bagasse-sugarcane-Fe3O4 linkage. The supported magnetite revealed a pollutant degradation rate of 99%, which deeply highlights an activity improvement after Fe3O4 deposition on plasma-activated bagasse sugarcane. The reusability of supported-Fe3O4 catalyst revealed a pollutant degradation rate of 95% after the fourth cycle, thus highlighting its easy recovery and catalytic stability (reuse).

Polymers doi: 10.3390/polym18141729

Authors: Francis Franklin Will Nightingale Jovan Tanasković Zorana Golubović

Rigid polyurethane foam was evaluated as a filler material for a tubular railway vehicle energy absorber. Cubic samples cut from a cylindrical PU foam sample with a density of 175 kg/m3 were tested under quasi-static uniaxial compression to determine the material’s compressive response and provide input data for finite element modelling. The experimental results showed a non-linear stress–strain response typical of cellular foams, while samples from the central region of the cylinder exhibited a lower stress response than those from the outer region. An Ogden foam material model was calibrated in Ansys using compression data obtained by experimental tests and then applied to numerical models of three absorber configurations: an empty steel tube, a fully foam-filled steel tube, and a foam-filled tube with an additional concentric steel core. The simulations compared the force–stroke response and absorbed energy of each configuration under quasi-static axial loading through a conical bushing. Over a 60 mm stroke, compared to the empty tube, the fully foam-filled tube absorbed an additional 16% energy and the concentric-core configuration absorbed an additional 9.5%. These results indicate that rigid PU foam filling can improve the quasi-static energy absorption capacity of tubular railway collision absorbers.

Polymers doi: 10.3390/polym18141728

Authors: Muhammet Aydın Maruf Hurşit Demirel Ercan Aydoğmuş

The development of sustainable polymer composites reinforced with renewable resources and advanced nanomaterials has attracted considerable attention for multifunctional engineering applications. In this study, an environmentally friendly epoxy-based biocomposite (EBC) reinforced with coconut shell powder (CSP) and graphene nanopowder (GNP) was successfully produced through a casting process. CSP was employed as a bio-based filler, while GNP was incorporated at concentrations ranging from 0 to 0.75 wt.% to improve the overall performance of the composites. The effects of GNP loading on bulk density, tensile strength, elongation at break, Shore D hardness, thermal conductivity, dielectric properties, thermal stability, mechanical and microstructural characteristics were systematically investigated. The results demonstrated that the incorporation of GNP significantly enhanced the multifunctional properties of the improved EBCs. Bulk density increased from 1137.5 to 1143.1 kg m−3 with increasing GNP content. The optimum tensile strength of 28.6 MPa and Shore D hardness of 77.4 were achieved at 0.45 wt.% GNP, indicating effective stress transfer and strong interfacial interactions between the epoxy matrix, CSP, and GNP. Thermal conductivity increased from 0.110 to 0.149 W m−1 K−1, while the dielectric constant increased from 3.06 to 4.25 with increasing GNP concentration. Thermogravimetric analysis revealed improved thermal stability and enhanced char formation in graphene-containing composites. FTIR analysis confirmed that graphene acted primarily as a physical reinforcement without altering the fundamental chemical structure of the epoxy network. SEM and EDX investigations demonstrated improved structural compactness, homogeneous filler dispersion, and successful graphene incorporation. The findings indicate that GNP and CSP reinforced EBCs possess significant potential for lightweight structural materials, thermal management systems, dielectric components, and sustainable multifunctional engineering applications.

Polymers doi: 10.3390/polym18141727

Authors: Manav Bhati Mohammad Atif Faiz Afzal Alex K. Chew Andrea R. Browning Mathew D. Halls

The glass transition temperature (Tg) is a pivotal design parameter for polymer performance across diverse applications, yet its rapid prediction within expansive chemical spaces remains a challenge. We present a machine learning (ML) framework for the high-throughput prediction of Tg in binary copolymers, trained on experimental datasets encompassing both homopolymers and copolymers. We evaluate various ML architectures, including graph-based algorithms, to effectively capture non-linear composition–property relationships. The optimized model achieves high predictive accuracy with an RMSE of ~14K and an R2 of ~0.98. Crucially, the framework accounts for the chemical diversity of monomeric units by integrating structural descriptors with molar composition ratios, enabling the model to capture complex dependencies of thermal stability on chemical structure and composition. We validate the model’s robustness using physics-based molecular dynamics (MD) simulations. To showcase the platform’s scalability, we generated a library of approximately 148,000 binary copolymer compositions and predicted their Tg, facilitating the rapid mapping of vast design spaces. This extensive virtual library enables the identification of optimal monomer pairings that would be experimentally inaccessible through traditional trial-and-error methods. Through these large-scale exploration studies, we demonstrate the ability to design copolymers for targeted applications, including a specific case study on elastomeric systems. This integrated approach, combining experimental data, ML modeling, and physics-based validation, offers a transformative path for the accelerated discovery and multi-property optimization of functional copolymers.

Polymers doi: 10.3390/polym18141726

Authors: Pawan Patel Dirk Romeis Marina Saphiannikova

Magneto-active elastomers (MAEs) are polymer composites consisting of magnetic microparticles embedded in an elastomeric matrix. These materials exhibit strong magneto-mechanical coupling under external magnetic fields, resulting in tunable stiffness, reversible shape changes, and nonlinear magnetic responses. This study presents a multiscale theoretical framework to investigate the origin of magnetic hysteresis in MAEs, with emphasis on the evolution of the internal microstructure during magnetization and demagnetization. The total energy of the system is formulated as the sum of magnetic and micromechanical contributions, while macroscopic deformation of a cylindrical MAE sample is fully constrained. Particle interactions are modeled first via pure dipole–dipole interactions and then extended to include higher-order near-field effects at close particle separations. The results show that hysteresis in MAEs with magnetically soft particles primarily arises from trapped microstructural rearrangements, leading to distinct particle configurations under increasing and decreasing magnetic fields. Parametric studies demonstrate that particle volume fraction, sample aspect ratio, and matrix stiffness strongly influence the microstructure evolution and the width of resulting hysteresis loops. The proposed framework provides a solid foundation for modeling magnetic hysteresis, which is essential for the design and optimization of MAEs in practical applications.

Polymers doi: 10.3390/polym18141725

Authors: Seunguk Lee Jeonghyeon Lee Chanhyun Lee Sehun Kim Jinwon Jo Young Chull Ahn

The continuous miniaturization of semiconductor and lithium-ion battery manufacturing processes has intensified the demand for stringent particulate control in cleanrooms while simultaneously increasing the importance of energy efficiency. However, conventional melt-blown (MB) electret filters suffer from severe filtration efficiency degradation under ISO 29463 discharge conditions, whereas glass fiber filters exhibit an excessive pressure drop. To address this trade-off, in this study we propose an electret–nanofiber hybrid multilayer filter and establish a dual-efficiency model for its systematic optimization. The proposed model integrates the slip flow effect of nanofibers and incorporates a structural resistance factor (β = 0.125) derived from the ultrasonic bonding process. Experimental validation demonstrates that the model achieves high predictive accuracy (R2 = 0.9995), and the optimized hybrid filter maintains > 98.1% filtration efficiency after ISO 29463-5:2022 discharge testing, markedly outperforming conventional MB filters (41.4%). Furthermore, the hybrid filter exhibits a quality factor (QF) of 0.117, more than twice that of commercial glass fiber filters. These findings demonstrate that the proposed model-based framework provides robust design guidelines for next-generation energy-efficient air filtration systems capable of meeting stringent international standards.

Polymers doi: 10.3390/polym18141724

Authors: Plamen Simeonov Velislava Todorova Tsvetelina Batsalova Balik Dzhambazov Stanislava Ivanova Plamen Katsarov

Xanthohumol (XN), a prenylated chalcone isolated from Humulus lupulus L., exhibits a wide range of biological activities, including antioxidant, anti-inflammatory, and chemopreventive effects. However, its therapeutic application is limited by poor aqueous solubility, low chemical stability, and rapid clearance from the systemic circulation. The present study aimed to develop and characterize a novel nano-sized drug-delivery system for XN that combines favourable colloidal stability, efficient encapsulation, sustained release, and reduced recognition by macrophages (“stealth-like” properties). To achieve this, XN-loaded cationic liposomes were coated with two marine polysaccharides, iota-carrageenan (CAR) and fucoidan (FUC), followed by Ca2+-mediated cross-linking. Liposomes were prepared by the ethanol injection method, and formulation parameters were optimized using a 23 + 1 full factorial design. Surface modification and cross-linking conditions were further optimized through polyelectrolyte titration and a Taguchi L9 orthogonal array. The resulting nanocarriers were evaluated for particle size, polydispersity, ζ-potential, encapsulation efficiency, release behavior, and cellular uptake. Both coatings significantly prolonged XN release compared with uncoated liposomes, with CAR-coated vesicles providing the most sustained release (≈55% over 48 h). In RAW264.7 macrophages, 50 µg/mL CAR-coated liposomes reduced cellular uptake by approximately 74% following 1-h incubation relative to uncoated controls and maintained this reduction over 2 h whereas FUC-coated vesicles afforded only transient early evasion. The cross-linked iota-carrageenan coating thus represents a promising strategy for conferring stable “stealth-like” characteristics to XN-loaded liposomes intended for prolonged drug delivery.

Polymers doi: 10.3390/polym18141723

Authors: Damla Nur Çelik Rüya Kılıç Demircan Güneş Mutlu Avinç Gökhan Kaplan

This study investigated the effects of precursor type, NaOH molarity, and thermal curing temperature on the performance of geopolymer mortars produced using fly ash (FA), ground granulated blast-furnace slag (GBFS), metakaolin (MK), and waste brick powder (WBP). Mortars were activated using 12 M and 16 M NaOH solutions at a constant Na2SiO3/NaOH ratio and thermally cured at 60 and 90 °C for 24 h. Physical, mechanical, transport, microstructural, and cost-performance properties were evaluated. The results demonstrated that the optimum activation conditions strongly depended on precursor type. MK-based mortars cured at 16 M–90 °C exhibited the best overall performance, achieving the lowest apparent porosity (6.1%) and water absorption (5.4%), and the highest oven-dry density (2194 kg/m3), compressive strength (25.8 MPa), and flexural strength (3.43 MPa). These mortars also exhibited the lowest capillary water absorption (1.88 kg/m2), the highest electrical resistivity (248.00 kΩ·cm), and the lowest charge passed (177 C), indicating enhanced pore refinement and chloride-ion penetrability. In contrast, GBFS performed better under milder activation conditions, whereas WBP showed lower performance due to its coarser, more crystalline structure. SEM/EDS analyses confirmed that the formation of dense aluminosilicate gel governed matrix quality and overall performance. Overall, MK activated at 16 M and cured at 90 °C provided the most favorable balance between technical performance and cost efficiency.

Polymers doi: 10.3390/polym18141722

Authors: Emrah Madenci Muhammed İhsan Özgün Ceyhun Aksoylu Yasin Onuralp Özkılıç

This study comprehensively investigates the thermal and mechanical degradation behavior of molded glass-fiber-reinforced plastic (GFRP) grating composites subjected to temperatures ranging from 80 °C to 320 °C. Three types of industrially produced GFRP gratings—open-type (OG), thin closed-skin (CG), and thick closed-skin (TCG)—were evaluated using mechanical, microstructural, chemical, and crystallographic analyses. Three-point bending tests revealed that TCG-type specimens exhibited superior thermal resistance, experiencing only a 43.9% loss in strength at 320 °C, whereas OG-type specimens showed significant resin degradation, fiber–matrix decomposition, and microcrack formation at temperatures above 200 °C. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed significant resin degradation, fiber–matrix decomposition, and microcrack formation. Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) confirmed substantial mass loss and structural disintegration at temperatures above 200 °C. Dynamic Mechanical Analysis (DMA) results revealed that the glass transition temperature (Tg) occurred at approximately 115–120 °C. The second-order regression model developed to estimate flexural strength under increasing temperature provided high accuracy (R2 > 0.99) for all grating types. It should be noted that this investigation focuses on the short-term thermo-mechanical response under fundamental flexural loading to provide an accurate baseline for preliminary engineering design. The findings emphasize that the effect of temperature should be considered a critical parameter in the structural design of GFRP systems, especially in industrial environments with temperatures above 120 °C. Accordingly, tables for material selection and load-carrying capacity should be recalibrated to account for short-term temperature effects.

Polymers doi: 10.3390/polym18141721

Authors: Lu Liu Hongrui Wang Caifeng Zhao Weiliang Zhang Hongke Xie Jianliang Tang Leping Zhang Yuan Yuan Longxin Jin Sai Shao

Stable rice production is critical for ensuring national food security and agricultural sustainability. Climate change is increasing the demand for efficient crop management strategies to maintain rice production. Foliar fertilization enables rapid nutrient supplementation by directly delivering nutrients to aboveground tissues while avoiding soil-related limitations. However, most foliar formulations are primarily designed for rapid nutrient delivery and have limited capacity to prolong water retention and nutrient availability on leaf surfaces after application. Hydrogels possess excellent water-retention and nutrient-delivery capabilities, but their intrinsic crosslinked networks limit water solubility and foliar suitability. Inspired by these characteristics, a sprayable polymer-based formulation was designed to combine hydrogel-like moisture preservation with foliar application compatibility. In this study, a foliar moisture-preserving synergist (FMPS) was developed using radiation-synthesized potassium polyacrylate as the polymer matrix, with urea and glucose incorporated as nitrogen and carbon sources, respectively. Structural characterization revealed morphological changes after incorporation of urea and glucose into PAA-K, while Fourier transform infrared spectroscopy suggested their incorporation and possible intermolecular interactions. Under standard growth conditions, FMPS increased the effective panicle number, filled grain number, and seed-setting rate by 29.3%, 18.4%, and 4.0%, respectively, resulting in significantly improved rice yield. These findings demonstrate the potential of FMPS as a hydrogel-inspired foliar formulation for enhancing rice productivity.

Polymers doi: 10.3390/polym18141719

Authors: Lyazat Tolymbekova Gaini Seitenova Aiymzhan Kazbekova Aisha Baktybek Murat Kassymzhanov Eldar Kopishev Zarina Yelemessova

The growing demand for polymer recycling requires effective approaches to improve the performance of recycled materials and expand their practical applications. In this study, electron-beam irradiation was investigated as a method for modifying recycled polyethylene obtained from façade-fastening elements. Virgin PE-80 polyethylene was used as a reference material for comparison. Irradiation was carried out using an ILU-10 electron accelerator (5 MeV) at doses of 95–125 kGy. Structural, morphological, elemental, thermal, crosslinking, and mechanical characteristics were evaluated using FTIR spectroscopy, SEM/EDS analysis, differential scanning calorimetry (DSC), gel fraction determination, and tensile testing according to ISO 527. The results showed that irradiation promotes the formation of a crosslinked network structure in both materials, as confirmed by the increase in gel fraction with increasing dose. For recycled polyethylene, gel fraction values increased from 46.7 to 56.2%, indicating effective radiation-induced crosslinking despite the structural heterogeneity of the material. FTIR analysis revealed the formation of oxygen-containing functional groups associated with radiation-induced oxidation, which was more pronounced in recycled polyethylene due to the presence of pre-existing defects and degradation products. SEM observations revealed increased surface roughness and localized fibrillar features after irradiation, while DSC analysis indicated a decrease in the crystallinity of recycled polyethylene associated with radiation-induced crosslinking and restricted molecular chain rearrangement. Mechanical testing showed an increase in tensile strength and elastic modulus accompanied by a reduction in elongation at break. Among the investigated irradiation doses, 110 kGy provided the most favorable balance between crosslinking efficiency and preservation of structural integrity. These findings demonstrate that electron-beam irradiation is an effective strategy for upgrading recycled polyethylene by improving its mechanical performance while maintaining structural integrity, thereby expanding its potential for reuse in circular economy applications.

Polymers doi: 10.3390/polym18141720

Authors: Pedro Rodríguez Sandoval Andres Felipe Rubiano-Navarrete Angie Natalia Cuy Talero Edwin Yesid Gómez-Pachón Ricardo Vera Graziano

The development of biodegradable composite materials offers a sustainable alternative to conventional synthetic polymers, particularly in short-lived applications. In this context, the incorporation of nanoscale reinforcements can improve mechanical properties without compromising the material’s degradability. The purpose of this study was to evaluate the composting behavior of a composite material based on low-density polyethylene (LDPE), potato starch, and cellulose acetate nanofibers (NFCA). The material’s degradability and mechanical stability were analyzed over 180 days according to the ASTM D5988 standard. The nanofibers were produced via electrospinning, yielding an average diameter of approximately 85 nm. The composite material was prepared using twin-screw extrusion followed by injection molding to produce ASTM D638 test specimens. The effects of biodegradation were evaluated through mass loss, CO2 generation in a desiccator, tensile testing, Shore D hardness measurements, and microstructural analysis via scanning electron microscopy (SEM). The results demonstrated a progressive increase in CO2 generation, particularly in the reinforced formulations (up to 111.76%). The formulation containing 3% NFCA exhibited the greatest mass loss (20.28%). Tensile testing revealed moderate reductions in maximum stress (1.66–8.44%), whereas hardness increased by up to 5.4% in the reinforced formulations. SEM analysis revealed increased porosity as the composting period progressed. The findings suggest that the incorporation of NFCA enhances biodegradative performance, as evidenced by increased CO2 evolution, mass loss, and morphological changes during composting.

Polymers doi: 10.3390/polym18141718

Authors: Wenyan Gu Xinyi Jin Jiaqiao Zhang Nannan Guo Yu Shi Jiang Shi Xiangrong Lan Licheng Zhu

Carbon nanotube (CNT)- and graphene flake (GF)-modified polyester (PET) nonwoven composites were prepared using a one-sided impregnation process with waterborne polyurethane (PU) as the binder. The objective of this work was to clarify how the geometry and loading of one-dimensional CNTs and two-dimensional GFs regulate conductive network formation, anisotropic mechanical behavior, and thermal response in PU/PET nonwoven composites. The novelty of the study lies in the direct comparison of CNT and GF fillers in the same nonwoven/PU matrix and in correlating filler morphology with mechanical reinforcement, electrical conductivity, and textile-related thermal management performance. The sample codes C5 and C6 represent CNT contents of 5 and 6 wt.%, respectively, while G4 and G6 represent GF contents of 4 and 6 wt.%, respectively. Scanning electron microscopy (SEM) showed that GF tended to form sheet-like coatings on fiber surfaces and to fill inter-fiber pores, whereas CNTs showed more local aggregation because of their high surface energy. The composites exhibited anisotropic tensile behavior, with higher tensile strength in the longitudinal direction than in the transverse direction. In the longitudinal tensile test, G4 reached a tensile strength of 13.01 MPa, while C5 reached 11.35 MPa. With increasing carbon material content, both the electrical and thermal conductivities of the composites increased. The electrical conductivity reached 0.02100 S/cm for C6 and 0.05893 S/cm for G6. The thermal conductivity of the CNT/PU/PET composites increased from 0.1163 to 0.1923 W/(m·K), whereas that of the GF/PU/PET composites increased from 0.1793 to 0.2537 W/(m·K). Infrared thermal imaging further indicated that carbon material addition produced faster heating and slower heat dissipation than the unmodified PU/PET sample. These results provide a useful reference for developing multifunctional nonwoven composites for smart textiles, special protective clothing, wearable thermal management layers, and flexible electronic textile substrates.

Polymers doi: 10.3390/polym18141717

Authors: Wenbo Jin Wenyu Ning Ruoyu Wang Danyang Zhao Liangkun Lu Fei Duan Jian Yang Cheng Zhang Kedong Song

The meniscus is a fibrocartilaginous tissue essential for load transmission, shock absorption, joint stability, and cartilage protection in the knee. However, its intrinsic healing capacity is severely limited, particularly in the avascular region and in complex defects, often resulting in persistent symptoms, functional impairment, and progressive joint degeneration. Although current clinical interventions, including meniscal repair, partial meniscectomy, allograft transplantation, and scaffold-assisted meniscal substitution, can provide symptomatic and functional improvement in selected patients, durable structural and functional restoration remains difficult to achieve. Meniscus tissue engineering has therefore emerged as a potential strategy for tissue preservation and functional reconstruction. This review synthesizes recent advances in meniscus tissue-engineered scaffolds, focusing on biomaterial systems, biofabrication strategies, and translational progress. Natural polymers, decellularized extracellular matrix, synthetic polymers, and composite materials are discussed according to their respective roles in biological regulation, mechanical support, structural organization, and clinical feasibility. Emerging biofabrication strategies are further analyzed with respect to geometric reconstruction, zonal organization, fibrous anisotropy, and their implications for scaffold evaluation. Finally, current in vitro, preclinical, and clinical evidence is critically examined to identify the key barriers that still limit long-term regeneration and clinical translation.

Polymers doi: 10.3390/polym18141716

Authors: Juliana Aristéia de Lima Ruud Cuypers Anders Höije Ignacy Jakubowicz Richard Sott Nazdaneh Yarahmadi

Acrylonitrile butadiene styrene (ABS) is widely used as an engineering plastic, but its extensive use generates a significant amount of waste that is difficult to recycle due to the material’s complex composition. In this study, the physical recycling of ABS using the dissolution technique has been employed to separate the pure copolymer of styrene and acrylonitrile (SAN) from polybutadiene rubber (PBR) and other substances. The relationships between the properties and composition of the original ABS materials were investigated as a starting point and for reference values to evaluate the effects of recycling on the quality and safety of recycled materials. Three different ABS materials were used in the recycling process from which pure SAN polymers were produced. The recycled SANs were then melt-blended with fresh masterbatch. The final ABS materials had the same composition, which facilitated investigation of whether the use of SAN recycled from different sources results in any differences in the properties of the final ABS material. The results showed that all the properties of ABS materials made with recycled SAN are similar regardless of the source of SAN. Several chemical substances were quantified in the original ABS materials and in SAN polymers obtained through the recycling process. The substances were largely removed from all materials except one. The main conclusions from this study are that the quality of ABS materials made with recycled SAN is at the same level as that of virgin ABS and is independent of the source from which SAN comes. This study has also shown that chemical safety is satisfactory because the physical recycling process is able to remove most of the substances that were present in the original ABS materials.

Polymers doi: 10.3390/polym18141715

Authors: Sandeep Bavanam Nagaraja Reddy Kishor Buddha Kadiyala Chandra Babu Naidu Dudekula Baba Basha

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Polymers doi: 10.3390/polym18141714

Authors: Naluemol Sriprasert Nantawan Krajangta Thanakorn Wasanapiarnpong Pavinee Padipatvuthikul Didron Thanasak Rakmanee

A novel alumina-filled ceramic-reinforced polymer (CRP) crown (Hassawat-01; HS) was developed. This study evaluated the effect of luting cement on the marginal and internal adaptation of HS and compared its performance with a commercial DLP-printed CRP (VarseoSmile Crown Plus®; VS) and a milled resin nanoceramic (Cerasmart® 270; CE). Ninety-nine crowns (n = 33/material) were fabricated with a 50 µm cement space and luted using Maxcem Elite®, RelyX Unicem®, or Ketac Cem® (n = 11/subgroup). Adaptation was assessed without and with cementation using micro-computed tomography at 160 measurement points per crown. Without cementation, HS demonstrated the most favorable internal adaptation, whereas VS showed the best marginal adaptation. Following cementation, gap dimensions increased in all groups. Despite its superior non-cementation fit, HS exhibited the greatest increase in marginal and internal discrepancies, suggesting increased hydraulic resistance during seating. Among the evaluated cement–crown combinations, VS luted with RelyX Unicem® showed the most favorable post-cementation adaptation. Post-cementation analysis was limited to HS and VS because the radiopacity of CE prevented reliable cement interface segmentation. These findings indicate that adaptation is influenced by both crown geometry and cement properties, and that highly adapted intaglio surfaces may require careful cement selection to optimize clinical fit.

Polymers doi: 10.3390/polym18141713

Authors: Yilin Liu Zhe Chen Jinlei Qu Baogang Zhang Le Kang Yongtao Qu

Electromagnetic interference (EMI) shielding materials are critical for reducing EMI pollution and enhancing information security. This study presents a systematic comparison of silver-plated copper (Cu@Ag; flake-like morphology; the average particle size D50 = 20.1 μm) and silver-plated aluminium (Al@Ag; spherical morphology; D50 = 47.5 μm) fillers with distinct morphologies incorporated into silicone rubber matrices via Rheomixer blending, open-mill compounding, and peroxide vulcanisation. This work aims to elucidate how filler morphology and multilayer sandwich architecture govern shielding efficiency and related material properties. The flake-like Cu@Ag fillers demonstrated superior low-loading performance. Due to their high aspect ratio and enhanced interfacial contact, Cu@Ag composites reached a critical loading for practical EMI shielding performance at 150 phr. In contrast, spherical Al@Ag fillers required a higher loading of 200 phr to achieve the same effect. Both composites achieved EMI shielding effectiveness exceeding 90 dB at 250 phr filler loading across the X-band frequency range (8.2–12.4 GHz). Innovatively, sandwich-structured composites were fabricated by combining Cu@Ag and Al@Ag layers through co-vulcanization, achieving approximately 110 dB shielding effectiveness, which is a ~33% improvement over single-layer composites at equivalent filler loading (200 phr). Analysis of the shielding mechanisms reveals that this enhancement results from multiple electromagnetic wave interactions, including increased reflection losses at morphologically distinct layer interfaces and enhanced absorption through conductivity gradients. This work demonstrates that a rational combination of flake-like and spherical fillers with contrasting morphologies and conductivity characteristics in multilayer architectures provides a powerful strategy for developing high-performance flexible EMI shielding materials.

Polymers doi: 10.3390/polym18141712

Authors: Hongjie Cao Yanli Sun Shaofeng Lu Bo Li Songcong Lin Qiancheng Yang Chengcheng Tian Fan Zhang

Solid–solid phase change materials integrate high heat storage, leak-proof performance, and dimensional stability, thereby positioning them as optimal candidates for thermoregulating textile applications. This study effectively synthesized PEG-based crosslinked waterborne polyurethane phase change materials (WPU-SSPCMs) with polyethylene glycol (PEG) as the soft segment, hexamethylene diisocyanate (HMDI) as the diisocyanate, and glycerol (GL) as the multifunctional chain extender. The effects of PEG molecular weight, diisocyanate type, chain-extension temperature, and monomer molar ratio on the phase transition behavior and thermal stability of WPU-SSPCMs were systematically investigated. The results indicate that at a PEG molecular weight of 2000, a chain-extension temperature of 70 °C, and a monomer molar ratio of n(PEG:HMDI:GL) = 1:2:0.67, the synthesized WPU-SSPCMs exhibited optimal comprehensive performance. The material demonstrated a melting temperature of 33.38 °C with a high enthalpy of 80.31 J/g. It displayed characteristic solid–solid phase transition behavior without evidence of liquid leakage during heating. Following 100 thermal cycles, the enthalpy variation remained below 1 J/g, indicating exceptional thermal and cycling stability. When applied to cotton fabric, the resultant thermoregulating textile displayed a buffering plateau during both heating and cooling processes, demonstrating a pronounced temperature-regulating effect relative to untreated fabric. The developed WPU-SSPCM holds considerable promise for applications in intelligent temperature regulation.

Polymers doi: 10.3390/polym18141711

Authors: Mei Huang Lei Yuan Junjun Ran Huili Liu Yaoxin Huang

This study addresses the inverse design of carbon fibre-reinforced polymer laminated plates with prescribed natural frequencies. The problem is difficult because stacking sequences are discrete, the design space is large, and multiple layups may produce nearly identical frequency spectra. This study does not seek to introduce a new tandem-network architecture. Rather, it adapts the established tandem inverse-design strategy to the discrete and non-unique vibration design of carbon fibre-reinforced polymer laminated plates. In the proposed framework, a trainable inverse network is coupled to a pre-trained forward frequency surrogate, allowing the inverse model to be optimised through frequency reconstruction instead of direct ply-angle supervision. A dataset of 50,000 symmetric CFRP laminates is generated using Classical Laminate Theory and a Rayleigh–Ritz vibration solver, covering four boundary conditions and a range of plate geometries. The forward model achieves R2 values above 0.99 and mean absolute percentage errors below 3% for the first five natural frequencies. Compared with a genetic algorithm, the proposed inverse model provides stacking sequences about 7000 times faster while producing multiple feasible designs for each target. Permutation sensitivity analysis shows that plate geometry has the strongest influence on the frequency response, followed by boundary condition and ply orientation. Four engineering cases confirm the method’s usefulness for vibration isolation, frequency-gap control, and multi-mode frequency prescription. The principal contribution is the integration of multi-boundary-condition vibration modelling, discrete stacking-sequence inverse design, response-based treatment of non-uniqueness, speed/diversity benchmarking, and sensitivity-based physical interpretation within a single composite-laminate design framework.

Polymers doi: 10.3390/polym18141710

Authors: Fang-Yu Hsu Shan-Ni Yu Wen-Shao Chang Jyh-Horng Wu

Wood-based composite panels are renewable and low-carbon materials, but their inherent flammability limits their broader use in applications requiring improved fire safety. In this study, expanded graphite (EG) was incorporated into a melamine–formaldehyde (MF) adhesive system to fabricate fire-retardant Japanese cedar (Cryptomeria japonica) plywood. Two EG types with different expansion ratios, 200-fold expanded graphite (200EG) and 450-fold expanded graphite (450EG), were added to the bonding layer at 10, 20, 30, and 40 phr. The effects of EG expansion ratio and content on the physicomechanical properties, combustion behavior, char morphology, and pyrolysis gas evolution of plywood were investigated. EG had limited effects on air-dried density and moisture content, but increasing EG content reduced bonding shear strength and parallel-direction flexural properties, particularly in the 450EG series. Cone calorimeter analysis showed that EG reduced the heat release rate and total heat release by promoting the formation of an expanded carbonaceous barrier layer. Among the tested formulations, 30 phr 200EG provided the most favorable balance between mechanical performance and fire-retardant efficiency, showing a visually more continuous char coverage while maintaining acceptable bonding properties. High-temperature furnace–FTIR analysis indicated that excessive EG loading or high-expansion-ratio EG increased CO2 and CO-related signals at 400–700 °C, probably because of a visually looser char morphology, structural disruption during expansion, and gas release from EG intercalating agents. Although the tested panels did not fully meet the CNS Grade 3 fire-retardant requirement, the results provide a useful basis for the modification and performance optimization of halogen-free fire-retardant wood-based composite panels.

Polymers doi: 10.3390/polym18141709

Authors: Baran Erkek Mehmet Şükrü Adin Ertan Kosedag Mateusz Bronis Ayşe Didem Erol Erkek Hamit Adin

Vehicle crash boxes are elements that protect the integrity of vehicles and ensure the safety of occupants in potential vehicle accidents. These crash boxes are mounted on the chassis of vehicles. In this study, composite crash boxes fabricated from aluminum, which is known for its lightweight properties, as well as denim and ultra-high-molecular-weight polyethylene, both of which are widely available on the market, were investigated experimentally. Composite crash boxes composed of an epoxy resin matrix reinforced with denim fabric (DenimFRP) and ultra-high-molecular-weight polyethylene (UHMWPEFRP) fibers, as well as aluminum (Al), were produced. The crash boxes were manufactured using a vacuum infusion method. This combination was produced by wrapping these fibers around an aluminum core. The energy absorption values, peak force values, and specific energy absorption values of the manufactured crash boxes were obtained through quasi-static compression tests and then compared. The best energy absorption value was achieved with the Al+denimFRP composite crash box manufactured by wrapping denim around aluminum at a workload of 1645.22 J, and its specific energy absorption value was also calculated as 15.52 J/g. The difference between the highest and lowest energy absorption was determined to be 244.61%. The highest peak strength value was obtained with the Al+denim+UHMWPEFRP sample, which contained a combination of aluminum on the inside, denim fabric in the middle, and UHMWPE fabric on the outside. Among the individually produced samples, the Al+denimFRP composite crash box manufactured with denim fiber exhibited higher results compared with the UHMWPEFRP composite box manufactured with ultra-high-molecular-weight polyethylene.

Polymers doi: 10.3390/polym18141708

Authors: Dilek Kurt Umut Kivanc Sahin

Coating method significantly influences how graphene derivatives perform on textile fibers, especially blended substrates where fiber chemistry varies. Graphene oxide (GO) and GO/fullerene composites were deposited on a blended fabric (45% PET, 25% viscose, 8% elastane, 22% recycled PET) using doctor blade and dip coating, followed by chemical reduction to rGO. Three thickness levels were applied for each method: blade gap settings of 50, 100, and 150 µm for doctor blade coating, and immersion times of 30 s, 2 min, and 5 min for dip coating. A more concentrated, higher-viscosity GO dispersion was prepared for doctor blade coating. FTIR spectra showed spectral changes consistent with chemical reduction in GO, including attenuation of hydroxyl-related absorption bands. Electrical resistivity and mechanical properties were determined via conductivity measurements and tensile testing. Doctor blade coatings achieved 0.81 kΩ/sq for rGO/fullerene at the highest thickness, 27 to 70 times lower than dip-coated samples (22.1–56.9 kΩ/sq), depending on coating material and level. The difference reflects uniform blade deposition on hydrophobic polyester fibers, whereas immersion leads to uneven particle distribution. Fullerene addition reduced sheet resistance by approximately fivefold. Mechanical testing showed that coating did not degrade fabric integrity; elongation values remained above 70% across all samples, with most exceeding 80%. These results suggest that, under the present processing conditions, the lower sheet resistance was mainly related to the more continuous coating morphology obtained by doctor blade coating.

Polymers doi: 10.3390/polym18141707

Authors: Kawisara Sirichaicharoenkol Anchan Khankhuean Weekit Sirisaksoontorn Chainarong Sakulthaew Ut Dong Thach Philip Anggo Krisbiantoro Kevin C.-W. Wu Chih-Feng Huang Tongsai Jamnongkan

Although polylactic acid (PLA) filaments are currently the leading biodegradable polymer in three-dimensional (3D) printing due to their excellent printability, good mechanical properties, and environmental friendliness, they possess low thermal resistance and limited flexibility, which restricts their use in applications requiring enhanced material performance. PLA filaments were reinforced with carboxymethyl cellulose (CMC) derived from durian husk using a single-screw extrusion technique to produce PLA/CMC filaments. CMC was obtained via carboxymethylation of durian husk-derived cellulose using monochloroacetic acid (MCA) in the presence of NaOH. The incorporation of CMC improved the thermal and mechanical properties of the PLA filaments. The presence of carboxylate (–COO–) groups from CMC makes the filaments promising as an adsorbent for a dye pollutant, namely, methylene blue (MB). Adsorption tests showed that the performance of PLA/CMC filaments for MB removal was influenced by the CMC loading, with 0.1 wt.% CMC (PLA/CMC-30 (0.1)) being the optimal one for achieving a higher adsorption rate. Over the filaments, the removal of MB followed a pseudo-first-order kinetic model, with a k1 of 0.020 min−1. Overall, this work demonstrates that PLA/CMC filaments derived from agricultural waste offer a sustainable and multifunctional material with enhanced performance for environmental remediation applications.

Polymers doi: 10.3390/polym18141706

Authors: Mikhail Serbinovsky Olga Popova

The formation technology, structure, and properties of composite membranes based on graphite materials obtained from hydrolytic lignin are studied. Lignin, a large-tonnage polymer waste with high energy potential, is an environmentally friendly and promising material for electrodes. Graphite obtained from lignin is characterized by high purity and fine dispersion, which contributes to its increased efficiency in electrochemical systems. Methods for forming membrane electrodes using various binders and solvents have been developed and have improved the mechanical and rheological properties of the composites. The introduction of surfactants and stabilizers into the paste-like composition contributes to the increased strength and ductility of the resulting materials. The study results show that optimization of the liquid phase composition and the selection of suitable binders are key factors in achieving high-performance characteristics in electrode materials. In particular, the use of aqueous–alcoholic solutions and various surfactants significantly improves the wettability and ductility of the pastes, facilitating the electrode formation process. The heat resistance of the obtained membranes is at least 630–650 °C, which makes them promising for use in modern energy storage systems.

Polymers doi: 10.3390/polym18141705

Authors: Husain Abbas Nadeem A. Siddiqui Mohammed S. Shaik Tarek Almusallam Yousef Al-Salloum

Existing analytical models for Fiber-Reinforced Polymer (FRP)-strengthened timber beams are generally limited to individual strengthening techniques and cannot readily accommodate hybrid reinforcement systems. This study develops a generalized analytical model to predict the flexural capacity of timber beams strengthened with near-surface-mounted (NSM) FRP bars, externally bonded FRP sheets, or their hybrid combination within a unified theoretical framework. The model is formulated based on internal force equilibrium and strain compatibility, incorporating a constitutive model for timber with linear elastic tensile behavior and a bilinear compressive stress–strain relationship including post-peak softening. The generalized formulation can be readily adapted to different strengthening configurations through appropriate simplifications. The proposed model was validated against experimental results obtained from four-point bending tests on small-scale timber beams strengthened with NSM GFRP bars and externally bonded GFRP sheets. The analytical predictions showed good agreement with the experimental results, with differences generally ranging from 2% to 23%, demonstrating satisfactory predictive accuracy. The experimental results further showed that the hybrid strengthening system increased the flexural capacity of the timber beams by up to 84% compared with the unstrengthened control beams, while also improving stiffness, ductility, and overall structural response. Failure was primarily due to timber tensile rupture and longitudinal splitting, whereas the GFRP reinforcement remained effective without rupture, indicating efficient utilization of the strengthening system. The proposed generalized analytical model provides a practical and reliable design tool for predicting the flexural strength of timber beams strengthened with various FRP reinforcement configurations, thereby supporting the structural rehabilitation and sustainable retrofitting of timber structures.

Polymers doi: 10.3390/polym18141704

Authors: Miha Brojan Jacopo Komic Enej Istenič

In this work, we develop a coupled multiphysics model that integrates polymer carriers exhibiting time-dependent thixotropic structural recovery with Darcy flow, linear Biot poroelasticity and advection–diffusion transport in a spherically symmetric, isotropic and homogeneous tissue domain. The formulation explicitly links rheological evolution to pressure-driven flow, interstitial deformation and solute transport through a unified framework, enabling systematic prediction of post-injection behavior. Unlike conventional approaches that assume constant carrier properties, the present model incorporates a time-dependent viscosity evolution, capturing the transition from an initially shear-thinned state to a recovered, highly viscous structure. Numerical simulations using hydroxypropyl methylcellulose and methotrexate parameters as representative components demonstrate that rapid post-injection viscosity recovery suppresses pressure-driven transport and diffusion, thereby enhancing local drug retention near the injection site. A systematic sensitivity analysis identifies the equilibrium viscosity as the dominant parameter controlling spatial localization, whereas tissue mechanical properties exert a comparatively minor influence. An effectiveness metric based on the Kullback–Leibler divergence reveals a tumor-size-dependent trade-off between spatial coverage and retention. The proposed framework thus introduces a predictive tool for analyzing coupled rheological-transport interactions and for the rational design and optimization of thixotropy-enhanced local chemotherapy strategies.

Polymers doi: 10.3390/polym18141703

Authors: Leimapokpam Romina Chanu Guo-Chung Dong Ping-Shan Lai

Reconstructing physiologically relevant in vitro tumor microenvironments (TMEs) that capture coupled biophysical and biochemical complexities remains a significant challenge in cancer modeling. Here, we present a tunable chitosan–gelatin–hyaluronic acid (HA) scaffold platform stabilized by Schiff-base (C=N) crosslinking to investigate how HA molecular weight (MW) affects scaffold architecture, hydration behavior, mechanical properties, degradation stability, and cancer cell organization. We established an isocompositional series of HA-containing scaffolds, with HA MW as the primary variable and polymer composition held constant across all HA-containing groups. Varying HA MW modulated pore morphology, swelling behavior, compressive modulus, and degradation profiles, demonstrating distinct effects on scaffold structural organization. Medium-MW HA yielded a balanced scaffold architecture characterized by high porosity, controlled swelling behavior, and stable mechanical performance under hydrated conditions. A549 cells exhibited a compact, spheroid-like organization, whereas PANC-1 cells displayed more protrusive, spread morphologies that varied with scaffold formulation. Conversely, HA-free scaffolds showed reduced structural stability and less organized three-dimensional (3D) cell morphology. Collectively, these findings substantiate that HA MW is an effective design parameter for tuning scaffold physicochemical properties and influencing scaffold-associated cancer cell organization in 3D culture. This study provides a tunable scaffold platform for future in vitro tumor microenvironment modeling.

Polymers doi: 10.3390/polym18141702

Authors: Anneke Scholz Ricky Selle Michael Großhauser

With the Green Deal and the Circular Economy Action Plan, the European Union aims to replace half of the fossil-based raw materials in plastics with sustainable alternatives by 2030. In the plastic pipe industry, the use of post-consumer recyclates (PCRs) remains very limited due to reduced material quality, economic hurdles, limited availability, non-specific classification requirements, and a lack of testing standards. This paper presents two interconnected contributions to the quality-assured use of PCR for buried utility infrastructure made from Polyethylene (PE), Polypropylene (PP), and unplasticized Polyvinyl Chloride (PVC-U). First, a methodological framework, based on EN 13476, defines suitability as the intersection of material classification and application-specific requirements profile. A review of the current regulatory and technical situation reveals a systemic discrepancy: requirements profiles are oriented toward virgin material, while the scope of classification for PCR remains insufficiently defined. As a result, PCR is either used without adequate suitability assessment or blended with fillers, thereby limiting recyclability. Secondly, the review focuses on additive strategies, including restabilization, compatibilization, chain modification, and recyclate-compatible functional additives. These strategies are among the main technical solutions for closing the gap between PCR properties and the product’s requirements, reducing filler dependency, and enabling the long-term use of PCR in safety-critical applications.

Polymers doi: 10.3390/polym18141701

Authors: Haocheng Liu Bowen Wang Zhiyao Fu Kai Ning Zhuan Jin Haining Wang Zhenglong Jiang

The long-term aging of HTV silicone rubber composite insulators under complex environments severely threatens power transmission line reliability. Traditional single/dual-parameter aging evaluation and lifetime prediction methods have low accuracy and poor generalization because they generally ignore multi-factor synergistic effects, pollution accumulation and electrical erosion. In this work, we systematically studied the aging characteristics of HTV silicone rubber under UV radiation, humidity, salt/ash contamination and their combined effects via accelerated aging tests and field sample verification, quantitatively analyzed the evolution of key mechanical, electrical and hydrophobic properties, and revealed the multi-factor synergistic aging mechanism from a micro–macro perspective with SEM, XPS and FTIR. The acceleration factor of the comprehensive accelerated-aging test was calculated as 43.8 through field-performance matching between 2000 h laboratory aging and 10-year field aging. We further established a “physical-pollution-electrical” three-dimensional evaluation system and constructed a multi-parameter synergistic lifetime prediction model through Pearson correlation analysis, VIF diagnosis and multiple stepwise regression. Compared with traditional dual-parameter models, the proposed model integrates physically interpretable degradation, contamination and electrical-stress indicators, thereby improving both prediction accuracy and engineering traceability. The model has 33% higher accuracy than traditional dual-parameter models, with average prediction errors of 0.55 years (same-manufacturer) and 1.0 years (cross-manufacturer). Five-fold cross-validation gives an MAE of 0.62 ± 0.08 years, and independent testing shows that most validation samples fall within the 95% prediction intervals, confirming favorable applicability within the present validation scope. These results provide theoretical and technical support for condition-based maintenance of composite insulators in power grids.

Polymers doi: 10.3390/polym18141700

Authors: Sana Javaid Azhar Mahmood Habib Nasir Mudassir Iqbal Naveed Ahmed Nasir M. Ahmad

In the original publication [...]

Polymers doi: 10.3390/polym18141699

Authors: Yangjie Huang Haixia Wang Yiyuan Zhang Yuhang Liu

Natural antioxidants are limited in food packaging due to poor stability and compatibility. A multifunctional film was successfully prepared via the incorporation of functional fillers into a guar gum/polyvinyl alcohol (GP) matrix. ZIF-8 was amino-functionalized to enhance rutin (Rt) loading, and the resulting ZIF-8-NH2@Rt was combined with purple sweet potato anthocyanins (PSPA) to fabricate a composite film for pork freshness monitoring. Compared with neat GP, the ZIF-8-NH2@Rt/PSPA/GP film showed a 30.6% increase in tensile strength and an elongation at break of 36.6%. The composite film also imparted exceptional UV-blocking capabilities, with light transmittance plummeting to 3.22% in the UVA region, 0.40% in the UVB region, and 47.53% within the visible light spectrum. The films displayed significant antioxidant properties, with DPPH and ABTS scavenging activities recorded at 73.27% and 67.64%, respectively. During pork storage, the film exhibited stable color changes. The G/R values corresponding to the limit of edibility were determined to be 0.78 and 0.67 for storage at 25 °C and 4 °C, respectively. The film was reusable for four cycles and extended the shelf life of pork by at least one day. These findings highlight the film’s considerable promise in the realm of smart food packaging and dynamic freshness tracing.

Polymers doi: 10.3390/polym18141698

Authors: Aysun Akpınar Merve Öztürk Önder Aybastıer Halil Çelik Gezu Ketema Janka Hüseyin Aksel Eren Semiha Eren

The development of bioactive surgical sutures capable of delivering therapeutic agents directly at the wound site has gained increasing attention in biomedical research. Functionalized sutures may provide localized antimicrobial or anti-inflammatory activity, potentially reducing postoperative complications and promoting tissue healing. In this study, absorbable surgical sutures were impregnated with carvacrol, a natural phenolic compound with well-known antimicrobial properties, using supercritical carbon dioxide (scCO2) technology. The impregnation process was carried out at 35 °C and 10 MPa for 120 min, allowing for the incorporation of carvacrol into the polymeric matrix of the sutures. The in vitro release behavior of the impregnated sutures was evaluated in phosphate-buffered saline (PBS, pH 7.4) at 37 °C over an 8-day period. The concentration of released compounds was determined by UV–Vis spectrophotometry using previously established calibration curves. An analysis of the experimental release data demonstrated that both carvacrol and benzydamine hydrochloride (HCl) (Tantum Verde®) exhibited a sustained release profile throughout the incubation period. Carvacrol release increased progressively from 2.02 ± 0.15 ppm on day 1 to 7.45 ± 0.15 ppm on day 7, followed by a slight stabilization on day 8 (7.25 ± 0.31 ppm). Similarly, benzydamine HCl (Tantum Verde®) release increased from 1.83 ± 0.11 ppm on day 1 to 3.29 ± 0.13 ppm on day 8. Release kinetics were analyzed using the Korsmeyer–Peppas model, indicating that the release mechanism was predominantly diffusion-controlled during the initial stage of the experiment. The results demonstrate that supercritical CO2 impregnation is an effective solvent-free technique for incorporating bioactive compounds into absorbable sutures, enabling controlled release under physiological conditions.

Polymers doi: 10.3390/polym18141697

Authors: Kait Kaarel Puss Eva-Lotta Palmiste Nikolai Treiberg Henry Vider Siim Pikker Ilona Faustova Siim Salmar

Lignin–cellulose mixtures (LCMs) generated as intermediates in wood biorefineries are commonly separated into lignin and cellulose. However, using ultrasound (US) to process these mixtures could create novel, valuable materials not possible with conventional methods. This study looked at how lignin affects the US modification of these mixtures. Crude and partially delignified LCMs were successfully prepared using aqueous solutions of EtOH, THF and dilute NaOH and then subjected to short, high-power US treatment. The resulting materials were characterised using FT-IR spectroscopy, particle size analysis, water retention value analysis, SEM and XRD. Sonication rapidly reduced the mean particle size, generating cellulose nanofibril-like structures in all samples according to SEM. The response depended strongly on lignin content, with samples containing lower amounts of lignin exhibiting substantially higher hydration capacity and stronger US responsiveness. At the molecular level, lignin removal exposes cellulose surfaces and enhances hydrophilic interface formation, increasing water uptake and suspension stability. Thus, results show that lignin limits accessible hydrophilic cellulose surface area rather than preventing fragmentation by sonication. US is therefore a chemical-lean strategy to tune the physicochemical properties of partly delignified LCMs and expand the product portfolio of integrated wood biorefineries towards novel advanced lignocellulosic materials.

Polymers doi: 10.3390/polym18141696

Authors: Mustafa Saleh Saqib Anwar Abdulrahman M. Al-Ahmari Abdelaty E. Abdelgawad Najeeb Al-khalli Abdullah Yahia AlFaify

This study statistically examines how fused deposition modeling (FDM) parameters influence the mechanical behavior of FDM-printed lattice structures. Diamond triply periodic minimal surface (D-TPMS) lattice structures were 3D-printed using carbon fiber-reinforced polylactic acid (PLA/CFs) composites. The effects of FDM parameters, including extruder temperature (ET), printing speed (PS), and layer thickness (LT), on the mechanical behavior of D-TPMS structures were investigated using response surface methodology (RSM). Uniaxial compression testing was performed to evaluate the mechanical properties of the 3D-printed samples, including compressive modulus (E), peak strength (σpeak), and specific energy absorption (SEA). The optimal FDM parameter settings for maximizing E, σpeak, and SEA were determined using multi-objective optimization via the desirability function. A deformation analysis was further conducted. The as-built D-TPMS samples generally matched the design relative density (44%), with absolute errors of 0.3–4.5%, while the largest deviation (~4.5% below the design value) occurred at low-ET and high-LT combinations. The results showed that LT was the dominant factor affecting E and σpeak, accounting for 77.45% and 89.25% of the total variation, respectively, whereas ET had the most significant influence on SEA, accounting for 55.76% of its total variation. In addition, increasing ET improved interfacial bonding and shifted the failure mode from early wall and layer fracturing to predominantly wall yielding, thereby enhancing structural integrity during compression. Higher LT deteriorated the mechanical properties (E, σpeak, and SEA) and promoted a progressive failure mode characterized by gradual interlayer separation. The findings revealed that the optimal settings (60 mm/s PS, 232 °C ET, and 0.2 mm LT) simultaneously maximized E (0.567 GPa), σpeak (15.937 MPa), and SEA (15.510 J/g), with high predictive accuracy (maximum % error ~±1.41%). Correlation analysis further revealed significant relationships between as-built relative density and the compression responses E, σpeak and SEA, with correlation coefficients exceeding 0.8. Overall, this study advances the understanding of how FDM printing parameters govern the mechanical behavior of PLA/CFs D-TPMS lattice structures and highlights the potential for predicting their mechanical performance.

Polymers doi: 10.3390/polym18141695

Authors: Amirthalakshmi Alavanthar Shubrajit Bhaumik Megha Sasidharan Nisha Kiran Mangalampalli Viorel Paleu Vitalie Florea

This study investigates the tribological performance of gum arabic (GA)-reinforced epoxy (EP) overlays on EN8 steel. Four GA concentrations (0.25, 0.5, 1, and 3 wt.%) were incorporated into the epoxy matrix to prepare overlays designated as EPGA1–EPGA4. Tribological performance was evaluated using a reciprocating tribometer under varying loads (5–20 N), sliding frequencies (1–2.5 Hz), and temperatures (40–70 °C). An L16 orthogonal array based on the Taguchi method was used to design the experimental matrix, and multi-criteria decision-making using the TOPSIS technique was employed to identify the optimum tribological condition based on minimum coefficient of friction (COF) and specific wear rate (SPWR). The optimum condition was obtained for the EPGA3 overlay (1 wt.% GA) at 5 N, 2 Hz, and 60 °C, which exhibited the lowest COF of 0.0567 ± 0.0021 and negligible wear. In contrast, the pure epoxy overlay showed severe adhesive wear, catastrophic delamination, a high COF of 1.15 ± 0.0023, and a wear rate of 163 × 10−8 mm3/Nm. Thermal characterization showed that GA improved the thermal stability and thermal transition behaviour of the epoxy matrix. Thermogravimetric analysis revealed an increase in onset degradation temperature from 320 °C for pure EP to 342 °C for EPGA4, while differential scanning calorimetry showed that EPGA3 exhibited the highest glass transition temperature (~118 °C), indicating improved interfacial interactions and restricted polymer-chain mobility. Nanoindentation and pull-off adhesion tests further confirmed the improved mechanical integrity and interfacial adhesion of the GA-reinforced overlays, demonstrating its potential as a sustainable reinforcement for tribological coating applications.

Polymers doi: 10.3390/polym18141694

Authors: Sundarakannan Rajendran Sakthivel Sankaran Yo-Lun Yang Kinga Korniejenko Thirumalai Kumaran Sundaresan Uthayakumar Marimuthu Koppiahraj Karuppiah

Fused deposition modelling (FDM) is increasingly used to produce high-performance polymer components; however, the mechanical performance of printed parts is often limited by weak interlayer adhesion, void formation, and residual thermal stresses. In this study, the effects of nozzle temperature, bed temperature, and post-treatment annealing temperature on the tensile and flexural strength of FDM-printed polyether ether ketone (PEEK) were investigated and optimized using Response Surface Methodology (RSM). A face-centred central composite design was employed to evaluate the individual, quadratic, and interaction effects of the three thermal parameters. The results showed that post-treatment annealing temperature was the most influential factor, contributing 56.48% to tensile strength and 52.73% to flexural strength, followed by nozzle temperature, which contributed 30.56% and 30.15%, respectively. Bed temperature showed a comparatively smaller individual effect; however, its interaction with nozzle temperature significantly influenced both tensile and flexural strength. The confirmation experiment performed at 200 °C post-treatment temperature, 414 °C nozzle temperature, and 142 °C bed temperature produced a tensile strength of 55.65 MPa and a flexural strength of 81.08 MPa, with prediction errors of 5.63% and 4.08%, respectively. SEM fracture analysis provided qualitative evidence that improved thermal processing reduced interlayer separation and visible void-related defects while promoting a more cohesive fracture morphology. These improvements are attributed to enhanced interlayer fusion, possible polymer-chain diffusion across layer boundaries, and thermal-stress relaxation during annealing. The findings demonstrate that thermal-parameter optimization and post-treatment annealing can improve the mechanical performance of FDM-printed PEEK within the investigated processing window.

Polymers doi: 10.3390/polym18141693

Authors: Manel Ben Abdallah Imen Saadaoui Touria Bounnit Ghamza Al-Ghasal Mahmoud Thaher Mohammad A. Al-Ghouti Nabil Zouari Helmi Hamdi Mohamed Chamkha Sami Sayadi

With the increase in Qatar’s population, the generation of plastic waste has grown, resulting in high levels of environmental pollution. Polyhydroxyalkanoates are sustainable bio-alternatives to petrochemical plastics. Despite their market potential, the industrial implementation of PHAs is still limited. This study aimed to develop sustainable processes for PHA accumulation by screening and isolating novel haloarchaeal strains from Qatari extreme environments with the ability to convert carbon sources to PHAs. In total, 24 positive haloarchaeal members, belonging to Natrinema, Haloarcula, and Halostagnicola genera, were identified for the first time in Qatari ecosystems through 16S rRNA and phaC/phaE gene sequence analyses. Among them, the promising PHA-producing archaeon Haloarcula sp. PLQ exhibited the highest production, reaching a PHB concentration of 496 ± 24 mg L−1 and a cell dry weight of 1109.8 ± 58.6 mg L−1, corresponding to a maximum yield of 44.69 wt % ± 2.13 under optimal conditions. Polymer characterization confirmed the production of poly(3-hydroxybutyrate). In addition, the thermal properties analyzed by TGA (Tonset = 250 °C; Td = 270 °C) and DSC (Tm = 169 °C) confirmed a PHB-like film with thermal behavior comparable to standard PHB. Therefore, future pilot-scale studies on the pure culture of a promising strain for PHA production from renewable feedstocks under non-sterile, batch, or continuous fermentation will be conducted.

Polymers doi: 10.3390/polym18141692

Authors: Anar Arinova Alfrendo Satyanaga Gulnur Kalimuldina Rezat Abishev Eriko Dewangga Saltanat Orazayeva Jong Kim

This study presents the development and evaluation of a hydrogel-based superabsorbent polymer sensor (HSPS) for measuring soil suction and establishing the soil–water characteristic curve (SWCC) of unsaturated soils. Polyacrylamide (PAM) hydrogels were synthesized via UV-induced free radical polymerization using acrylamide with varying crosslinking degrees. The polymers were characterized through FT-IR and TGA analyses, confirming successful synthesis and high thermal stability. Swelling, water retention, and kinetic behavior were systematically investigated. Results indicated that lower crosslinking density significantly enhanced swelling capacity, reaching up to 3000% in distilled water, while saline environments reduced absorption due to ionic screening effects. Swelling kinetics followed anomalous (non-Fickian) diffusion behavior and were well described by the pseudo-second-order Schott model. The synthesized polymers were integrated into a modified high-sensitivity pressure sensor operating on the osmotic principle to measure matric suction. The system was validated using natural soil. Among the tested formulations, the HSPS-3 demonstrated the most reliable suction measurements, reaching values up to approximately 1 MPa without significant temperature sensitivity. The resulting SWCC exhibited bimodal characteristics consistent with the soil’s dual pore structure. The proposed method provides a cost-effective, simple, and efficient alternative for suction measurement, expanding the practical range of SWCC determination in unsaturated soil mechanics.

Polymers doi: 10.3390/polym18141690

Authors: Oguzkan Senturk Rupesh Daripa Vivekkumar Chaubey Tirdad Boroomand Tobias Stirl Rajeev Gupta

This study investigates the mechanical performance and fatigue behavior of a woven glass fiber-reinforced epoxy laminated composite classified as IEC 60893 EPGC 203, widely used in structural insulating components for high-voltage (HV) equipment. With evolving energy infrastructures introducing dynamic and cyclic loading conditions, understanding the long-term mechanical reliability of such materials has become increasingly important. A comprehensive experimental program was conducted, including flexural, compressive, tensile, Charpy impact, and fatigue tests. Mechanical properties were evaluated according to relevant ISO standards at room temperature and 120 °C to assess temperature-dependent performance. Fatigue tests were performed under fully reversed loading conditions (R=−1), and stress–life (S-N) curves were established. The results revealed notable reductions in strength and stiffness at elevated temperature, together with progressive damage accumulation under cyclic loading. Failure features observed after fatigue testing were correlated with static mechanical properties to improve understanding of degradation behavior. The study is limited to the mechanical and fatigue characterization of EPGC 203 and does not include dielectric evaluation. Therefore, its relevance to HV applications is considered from the standpoint of the mechanical reliability of structural insulating components. The findings provide essential insights into the durability and reliability of EPGC 203 composites under realistic service conditions.

Polymers doi: 10.3390/polym18141691

Authors: Nina Žibret Tine Vojska Peter Bukovec

The application of lignin as a sustainable replacement for phenol in resin is one of the main priorities in the polymer industry. The partial substitution of phenol by Kraft lignin in the synthesis of resole resin, a mineral and glass wool insulation binder, was thus investigated. Lignin was activated by phenolation in an alkaline medium at low temperature, followed by reaction with formaldehyde in the same batch. Conducting the phenolation reaction in an alkaline medium allows the synthesis of resol resin to continue without interrupting the process, while the low temperature ensures the low viscosity of the synthesized resol, which is a prerequisite for its use as a binder in the manufacture of thermal insulation products. This is an important innovation that streamlines the production of modified resol. Activated lignin and resole resins were characterized by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). Phenolation occurs mainly via the binding of phenol to the lignin macromolecule, increasing the molecular weight of activated lignin, with only small amounts of low molecular weight species observed. Resol resins with and without incorporated lignin have identical FTIR spectra and similar molecular weight distributions, which confirms the successful synthesis of lignin-containing resin. With essential relevance for the undisturbed production of thermal insulation products, the most suitable of the resins synthesized with lignin has appropriate viscosity, double the stability of the reference product, and half the amount of tetradimer (tetradimer can cause problems due to precipitation). In addition, this resin results in significantly lower emissions and has increased flexural strength. The synthesis is transferable to industrial practice.

Polymers doi: 10.3390/polym18141689

Authors: Panya Dangwilailux Natworapol Rachsiriwatcharabul Putipong Lakachaiworakun Visit Eakvanich Wassachol Wattana Wachara Kalasee

The development of bio-based adhesives has emerged as a viable strategy to reduce fossil-derived resin consumption in wood and wood-based panel applications. This review provides a polymer-focused assessment of adhesive systems derived from proteins, carbohydrates, lignin, and tannins, emphasizing molecular architecture, crosslinking chemistry, interfacial interactions, and structure–property relationships. Adhesive performance is primarily dictated by functional group density, crosslinking efficiency, and network topology. Protein-based adhesives rely on hydrogen bonding and covalent crosslinking with lignocellulosic substrates but require structural modification to improve hydrothermal stability. Carbohydrate-based systems, including starch and cellulose derivatives, offer reactive hydroxyl functionalities that enable oxidation, esterification, and etherification pathways for enhanced network formation. Lignin and tannins, characterized by phenolic and aromatic structures, facilitate condensation reactions and enable partial substitution of phenol in thermosetting resins, supporting low-formaldehyde or formaldehyde-free formulations. Hybrid polymer networks, particularly protein–carbohydrate and lignin-modified systems, demonstrate improved crosslink density, reduced hydrophilicity, and enhanced mechanical performance. Life cycle analyses indicate that increasing biogenic carbon content and minimizing fossil-based cross-linkers can lower global warming potential (GWP) and volatile organic compound (VOC) emissions. Overall, a structure–property–sustainability framework is proposed to guide molecular design and performance optimization of next-generation bio-based wood adhesives.

Polymers doi: 10.3390/polym18141688

Authors: Shiqi Gao Minzhen Liu Jiteng Sun Zhicheng Su Ziyun Liao Peiyu Li Yunqi Jiang Can Fu Guangyu Pan

To address the challenges associated with prolonged inflammatory phases and delayed healing in clinically infected wounds, this research developed a multifunctional PB@GC@OD hydrogel integrating self-healing properties, injectability, and photothermal antibacterial efficacy. The hydrogel was constructed using oxidized dextran (OD) and glycol chitosan (GC) as the matrix, which were dynamically cross-linked via a Schiff-base reaction to form the GC@OD hydrogel. Subsequently, the photothermal agent prussian blue (PB) was incorporated to fabricate the PB@GC@OD hydrogel. The resulting PB@GC@OD hydrogel demonstrated robust self-healing capabilities and excellent injectability. Upon exposure to 808 nm near-infrared (NIR) irradiation, the hydrogel achieved efficient photothermal conversion, rapidly inducing localized hyperthermia that effectively eliminated Staphylococcus aureus, Escherichia coli, and methicillin-resistant Staphylococcus aureus (MRSA). In a mouse model of MRSA-infected wounds, the hydrogel not only maintained a moist wound microenvironment but also eradicated pathogenic bacteria via photothermal therapy, thereby significantly accelerating the healing process. Moreover, the hydrogel demonstrated favorable biocompatibility and long-term safety. Therefore, the PB@GC@OD hydrogel integrates photothermal sterilization, self-healing, injectability, hemostasis, and biocompatibility into a single platform, presenting a promising strategy for synergistic therapy and tissue regeneration in bacterially infected wounds.

Polymers doi: 10.3390/polym18141687

Authors: Mingkuan Wang Jiaheng Yao Long Zhang Ang Gao Enchao Zhang Shimin Zhang Xiaoxiao Zhu

To accurately characterize the nonlinear hyper-viscoelastic mechanical behavior of rubber materials under large deformation and stress relaxation conditions, this study investigates fluororubber (FKM) and hydrogenated nitrile rubber (HNBR) with different hardness levels through uniaxial mechanical tests and stress relaxation experiments. A constitutive parameter identification method based on hyperelastic models and the parallel rheological framework (PRF) model is established. First, several representative hyperelastic models, including the Neo-Hookean, Mooney–Rivlin, Yeoh, Ogden, Arruda–Boyce, and Van der Waals models, are comparatively evaluated. The results show that the Ogden model with (N = 3) provides the highest fitting accuracy for the large-deformation responses of FKM and HNBR with different hardness levels, with coefficients of determination (R2) ranging from 0.9879 to 0.9948. Subsequently, the Prony series parameters are identified from the stress relaxation data and converted into the initial parameters of the linear PRF model. To overcome the limitations of the linear PRF model in predicting nonlinear relaxation behavior, the PRF parameters are further optimized using the Isight data matching method combined with the Hooke–Jeeves algorithm. Finite element validation demonstrates that the optimized nonlinear PRF model can accurately predict the stress relaxation behavior of both FKM and HNBR. The mean absolute percentage errors of FKM60, FKM70, and FKM80 are 2.67%, 1.57%, and 2.56%, respectively, while those of HNBR60, HNBR70, and HNBR80 are 2.16%, 2.72%, and 2.58%, respectively. These results indicate that the combination of the Ogden (N = 3) hyperelastic model and the optimized nonlinear PRF model can effectively describe the large-deformation and time-dependent viscoelastic responses of rubber materials, providing a reliable constitutive modeling basis for finite element analysis and parameter calibration of rubber sealing structures.

Polymers doi: 10.3390/polym18141686

Authors: Hamdi Kuleyin

Lattice structures are widely utilized in lightweight engineering due to their design flexibility and tailorable mechanical properties. However, polymer lattices often exhibit limited load-bearing capacity and moderate crashworthiness under compression. This study proposes a hybrid reinforcement strategy based on the integration of carbon fiber-reinforced polymer (CFRP) rods into polymeric Kelvin-cell lattices. The specimens were manufactured via masked stereolithography, and the effects of rod placement pattern, the number of rods, and rod-length configuration were systematically investigated under quasi-static compression. Crashworthiness was evaluated in terms of force–displacement response, deformation mode, and crashworthiness metrics. Compared with the empty Kelvin-cell lattice, the best-performing hybrid configuration increased energy absorption, specific energy absorption, and mean crushing force by approximately 356%, 307%, and 356%, respectively. Mechanistically, distributed rod placement promoted more uniform load sharing, while the effect of increasing rod number depended strongly on the rod-length configuration. In addition, delayed or sequential reinforcement strategies provided superior performance and an enhanced balance between energy absorption and force efficiency. Regression models and ANOVA consistently identified rod-length configuration as the dominant design variable. These findings demonstrate that CFRP rod reinforcement can effectively enhance the crashworthiness of polymeric Kelvin-cell lattices, provided that the rod placement pattern, rod number, and rod-length configuration are designed jointly.

Polymers doi: 10.3390/polym18141685

Authors: Hsiuying Wang

Bamboo, a fast-growing and sustainable biomass, has traditionally been used in structural applications; however, its hierarchical architecture and rich chemical composition enable both the derivation of advanced nanomaterials and the fabrication of bamboo-assisted nanostructures. Recent studies demonstrate that such bamboo-based nanomaterials, including nanocellulose, lignin nanoparticles, silica nanoparticles, carbon dots, and carbon-based nanostructures, exhibit unique physicochemical properties suitable for biomedical applications. This review provides an overview of bamboo biology and classification, chemical composition, extraction and synthesis of bamboo-derived nanomaterials, and their biomedical applications. Emphasis is placed on their diverse biomedical applications, including drug delivery, tissue engineering and regenerative medicine, wound healing and antimicrobial dressings, cancer therapy, antioxidant and anti-inflammatory applications, and biomedical imaging and biosensing. In addition, emerging approaches that integrate bamboo-derived materials with plant-based bioactive compounds, particularly rose-derived phytochemicals, are proposed as promising strategies for achieving synergistic, broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. Overall, bamboo-based nanomaterials offer a sustainable and versatile platform for next-generation nanomedicine, with significant potential for future biomedical innovations.

Polymers doi: 10.3390/polym18141684

Authors: Thanikodi Sathish Vinayagam Mohanavel Thandavamoorthy Raja Sinouvassane Djearamane Palanivel Velmurugan Omaima Nasif Saleh Alfarraj Ling Shing Wong Velu Manikandan Manikkam Ravichandran

The Journal retracts the article “Influence of Compression Molding Process Parameters in Mechanical and Tribological Behavior of Hybrid Polymer Matrix Composites” [...]

Polymers doi: 10.3390/polym18141683

Authors: Jin Liu Long Chen Ge Gao Fei Ren Yukui Cai Zhanqiang Liu

Polyetheretherketone (PEEK) is a favorable material in bone tissue engineering due to its excellent mechanical properties and biocompatibility. However, as PEEK is biologically inert, this study introduced hydroxyapatite (HA) and graphene oxide (GO) to modify PEEK, and PEEK/GO/HA composites were prepared via compression molding and sintering. Molecular dynamics simulation results indicated that the Young’s modulus of the composite increased with rising HA content. The trends in the bulk modulus and shear modulus suggested a possible downward trend around HA contents of 10 wt% and 20 wt%; this may be attributed to the polarity mismatch between HA and PEEK, as well as the composite preparation process. The thermal conductivity of the composites exhibited a similar trend, with the thermal conductivity decreasing until the HA content reached 30 wt% due to interfacial thermal resistance between PEEK and HA. Concurrently, in vitro cell culture experiments were conducted on the precursor powder mixture to investigate the effect of the composition ratio on biological properties. The results indicated that cell viability was higher when the HA content was 30 wt%. This demonstrates the significant potential of PEEK/GO/HA composites in the field of bone tissue engineering.

Polymers doi: 10.3390/polym18141682

Authors: Mihai Parparita Paul Bere Razvan Udroiu Mircea Cristian Dudescu

Sandwich structures have gained much interest in drone manufacturing structures based on their lightweight design and excellent mechanical characteristics. In this work, a new solution for lightweight drone wing structures consisting of a thin sandwich skin, a main spar, and ribs was proposed. Seven sandwich structures based on prepreg-based CFRP skins and different cores were proposed for the wing drone sandwich skin. Thus, sandwiches with different chemical configurations and densities, such as ROHACELL 51, AIREX T92.100, balsa, AIREX R82.150, AIREX C71.75, NOMEX ECA-I, and Soric XF, were autoclave-manufactured and investigated. All the samples were tested under three-point bending. Also, microscopic analysis of the fracture zones was performed to establish a direct link between macroscopic flexural behavior and local failure mechanisms. A statistical analysis based on ANOVA with Box–Cox transformation followed by Tukey’s Honestly Significant Difference test was performed for flexural strength and flexural modulus. The results show that the sandwiches containing Soric XF foam with 62.5 kg/m3 density had the best mechanical properties, with a 71.66 MPa flexural strength and a 10,039 MPa flexural modulus.

Polymers doi: 10.3390/polym18141681

Authors: Ersin Ayhan Mehmet Kadri Değer Murat Doğruyol

This study investigates the thermo-mechanical and microstructural performance of concrete incorporating waste tire rubber (WR) and recycled steel fibers (WS) under elevated temperatures. Four mixtures were prepared: plain concrete (PL), rubber-modified concrete (WR5), and hybrid mixtures containing 0.4% and 0.8% steel fibers (WS0.4WR5 and WS0.8WR5). Specimens were exposed to temperatures of 400 °C, 600 °C, and 800 °C to simulate fire conditions. The results indicate that the incorporation of rubber reduces compressive strength at ambient temperature due to its lower stiffness and weak interfacial bonding. However, the addition of recycled steel fibers significantly improves crack resistance and enhances thermal stability. At 400 °C, the WS0.8WR5 mixture showed a retention rate of 92.9% (absolute strength: 44.32 MPa), compared to 72.2% for plain concrete (absolute strength: 44.11 MPa). Although the hybrid mixture has a lower ambient strength (47.68 MPa vs. 61.07 MPa), its superior retention makes it competitive in fire scenarios. Ultrasonic pulse velocity (UPV) measurements revealed a strong correlation with compressive strength degradation, confirming its effectiveness as a non-destructive indicator of internal damage. Microstructural analyses (SEM, XRD, and TGA-DTA) demonstrated that elevated temperatures lead to dehydration, phase transformation, and increased porosity, while steel fibers help maintain matrix integrity through crack-bridging mechanisms. The findings highlight a synergistic interaction between waste rubber and steel fibers, offering a sustainable and effective approach for improving the fire resistance of concrete.

Polymers doi: 10.3390/polym18131680

Authors: Zhongbin Xu Shushan Song Xiang Zhen Akram Ali Nasser Mansoor Al-Haimi Zhongming Wang Guocai Tian

In this paper, a novel biobased phenol formaldehyde resin foam was fabricated. Specifically, lignosulfonate, a byproduct of paper and pulping, is hydroxymethylated with paraformaldehyde and then condensed with phenol to form lignosulfonate-based phenol formaldehyde (LPF) resin, subsequently undergoing foam technology to prepare LPF foam. The structures and properties of the intermediate and target products were characterized by 1H nuclear magnetic resonance (1H NMR) spectroscopy, gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry derivative thermogravimetry (TGA-DTG), scanning electron microscopy (SEM), compression performance test, limiting oxygen index test and thermal conductivity measurement. It was found that the prepared foam exhibited excellent mechanical and thermal properties. At a lignin substitution degree of 10%, the optimal thermal stability (at 800 °C), compressive strength (0.14 MPa) and thermal conductivity (0.0294 W/m·K) were achieved. As the lignosulfonate content gradually increases, the limit oxygen index initially showed a significant increase and then decreased. It is worth noting that when the LS substitution degree is increased to 30%, the limiting oxygen index of foam is up to 32.6%. These results underscore the application potential of industrial lignin as a promising biobased substitute in the synthesizing PF foam with excellent thermal insulation and flame-retardant properties.

Polymers doi: 10.3390/polym18131679

Authors: Karla Katiushka Solís-Arévalo Luis J. Galán-Wong Aida Rodriguez-Garcia Katiushka Arévalo-Niño

Healthcare-associated infections are prevalent in hospitals, clinics, and long-term care facilities. The use of wound dressings on active skin wounds, like burns, can cause damage to the skin barrier when removed for cleaning. Electrospun biodegradable and biocompatible membranes have emerged as promising alternatives for wound dressing applications. In the present study, an electrospun membrane composed of polyvinyl alcohol/kefiran/schizophyllan loaded with gentamicin and ascorbic acid was developed. Kefiran was obtained from kefir with a 0.61% extraction yield. Beadless electrospun membranes with a diameter of 400 nm were obtained. Antimicrobial activity of the membrane against Staphylococcus aureus and Pseudomonas aeruginosa was determined. Growth inhibition halos of 16.4 ± 2.2 mm were found for Pseudomonas aeruginosa. Furthermore, the membrane cytocompatibility assay of the membrane showed no cell toxicity in human dermal fibroblasts (HDFn cells). The produced membranes showed potential to be used as a wound dressing material in the future.

Polymers doi: 10.3390/polym18131677

Authors: HanJiong Ji Shengqiang Liao Shibo Wu Sijia Chen Xue Guan Chenlong Li Dawei Zhang

The skin is the largest organ of the human body and, due to its direct contact with the external environment, is one of the most vulnerable tissues. Traditional medical bandages and gauze exhibit limited efficacy in wound management, often neglecting the control of wound inflammation and the promotion of skin regeneration. Hydrogels, as an emerging material, possess appropriate swelling capacity, oxygen permeability, and the ability to absorb wound exudates, thereby facilitating wound healing, making them an ideal choice for functional applications in skin tissue engineering. In this study, dual-treated balsa wood (BWSM) was used as the hydrogel substrate, with polyvinyl alcohol (PVA), chitosan (CS), and zinc gluconate (ZnG) used as the primary raw materials. The BWSM/PVA/CS/ZnG hydrogel was prepared via gamma-ray irradiation. Balsa wood treated with alkaline solutions, hydrogen peroxide solutions, and microwave treatment processing exhibited enhanced transparency, increased porosity, improved thermal stability and swelling rates, while retaining adequate mechanical strength. Gamma-ray irradiation of the BWSM/PVA/CS/ZnG hydrogel wound dressing demonstrated sustained drug release and antibacterial efficacy through release and antimicrobial tests. Animal experiments showed that the BWSM/PVA/CS/ZnG composite hydrogel promoted wound healing in mice and effectively prevented scar formation. The aforementioned results demonstrate that the PVA/CS/ZnG composite hydrogel loaded with balsa wood exhibits durable antibacterial properties and high mechanical strength and promotes wound healing, making it suitable for applications in biomedical materials such as wound dressings.

Polymers doi: 10.3390/polym18131678

Authors: Yura Choi Namchul Cho

Glass-transition-driven shape memory polymers are promising materials for 4D printing because their thermally activated transition enables programmed deformation and recovery without relying on melting or crystallization-driven switching. In this study, PDMS-MMA-modified photocurable networks were designed for vat photopolymerization-based 4D printing by varying PDMS-MMA content and switching monomer structure while maintaining a fixed TMPTMA crosslinker content. The resin formulations were prepared using tert-butyl acrylate (tBA) or isobornyl acrylate (IBOA) as switching monomers, PDMS-MMA as a flexible mobility-regulating segment, and TMPTMA as a multifunctional crosslinker. The effects of formulation composition on printability, network formation, thermal stability, thermomechanical transition, mechanical properties, and shape memory behavior were systematically investigated. FT-IR analysis confirmed effective photocuring of the acrylate/methacrylate networks, while rheological evaluation showed that resin viscosity depended on monomer structure and PDMS-MMA content. DMA results revealed thermomechanical transition, although some formulations exhibited broad tan δ responses due to network heterogeneity and distributed segmental relaxation. Based on resin printability, printed-part resolution, and relatively well-defined tan δ transitions, T-15 and I-15 were selected as representative formulations for quantitative shape memory evaluation. Shape memory testing was conducted under force-control mode because stable strain-controlled programming was not achievable for the printed specimens. Both T-15 and I-15 exhibited high shape fixity over two programming–recovery cycles. I-15 showed stable recovery behavior with recovery ratios of 91.51% and 95.87%, whereas T-15 showed apparent over-recovery with recovery ratios exceeding 100%, likely due to residual stress release during reheating. Overall, these results demonstrate that thermally activated shape-memory performance is governed not only by the nominal transition temperature but also by the coupled effects of PDMS-mediated segmental mobility, switching monomer structure, mechanical integrity, and elastic energy storage within a fixed crosslinked network framework.

Polymers doi: 10.3390/polym18131676

Authors: Al Mamun Maha Alruwaili Abdullah Al–Mamun Md. Shafiquzzaman Gary S. Coombs Aljawad Mohammed Alolaywi Amira Salman Alazmi

Crystallization can be exploited as an architecture-forming step for polymer membranes because it builds a load-bearing semicrystalline scaffold while simultaneously defining amorphous regions that later become transport pathways. Herein, we quantify how thermal history programs isotactic polystyrene (iPS) crystallization and translate the resulting microstructures into membrane-relevant design rules. Lux-calibrated digitally extracted pixel intensity (DPI) from polarized optical microscopy provides a quantitative, spatially resolved crystallinity proxy; benchmarking against differential scanning calorimetry confirms that the DPI proxy exhibits the same onset, peak, and completion signatures under matched temperature programs. The DPI–DSC agreement yielded R2 = 0.98 under matched programs. We compared crystallization initiated from molten and glassy states across a wide range of melt pretreatments and crystallization temperatures. Molten-state pathways display pronounced melt-memory behavior: modest changes in melt pretreatment shift induction time and half-time and drive textures from dense, fine spherulitic fields to sparse, coarser morphologies. In contrast, glassy-state crystallization largely suppresses melt history, yielding overlapping sigmoidal crystallinity curves and stable kinetic parameters consistent with relaxation-mediated nucleation. Avrami analyses indicate three-dimensional growth in both routes but highlight the strong melt-history sensitivity of apparent rate constants in the molten state. The crystallization rate and half-life show bell-shaped temperature dependence. Finally, saturated nucleation density correlates with the melting response, providing a practical link between kinetic observables and morphology. The processing–morphology map provides membrane-relevant design rules by linking thermal history to nucleation density and scaffold texture, which are expected to influence transport and mechanical stability in downstream membrane fabrication. In this study, “membrane architecture” is used in a pre-fabrication sense to denote the crystallization-programmed semicrystalline scaffold expected to govern subsequent pore-generation behavior and mechanical stability. Accordingly, the present work establishes a quantitative process–structure map for iPS scaffold design.

Polymers doi: 10.3390/polym18131675

Authors: Bingxuan Wang Tianfu Zhou Jiayu Li Yingjie Shi Meiqi Yang Yuxin Qian Yanzi Gao Meina Yu Cheng Zou Yuanwei Chen Huai Yang

Polymer-stabilized liquid crystal (PSLC) films are promising for smart window applications because of their transparent-to-scattering switching behavior. However, conventional acrylate-based PSLC films often suffer from poor mechanical robustness and weak interfacial adhesion, limiting their use in flexible devices. Herein, epoxy-based PSLC films have been prepared through radical-promoted cationic photopolymerization using a difunctional epoxy monomer, E6M, and a series of liquid-crystalline monoepoxy monomers, E-nOCB. The effects of alkyl chain parity, chain length, and E6M/E-10OCB ratio on polymer morphology, electro-optical behavior, and peel strength were systematically investigated. Even-numbered E-nOCB monomers favored the formation of regular columnar polymer structures and improved optical contrast, whereas odd-numbered monomers produced more disordered networks with higher peel strength. Among them, the sample prepared with E-10OCB showed a better balance between electro-optical performance and mechanical adhesion. At a fixed total polymer content of 15 wt%, optimizing the E6M/E-10OCB ratio enabled the sample doped with E-10OCB to achieve the highest contrast ratio of 160.91 while increasing the peel strength from 47.28 to 55.69 kPa compared with the sample without E-10nOCB. These results demonstrate that regulating monoepoxy/diepoxy composition and alkyl chain structure is an effective strategy for improving the overall performance of epoxy-based PSLC films for smart windows.

Polymers doi: 10.3390/polym18131674

Authors: Ziyan Shi Haibin Wang Huibin Sun Wei Huang

The spreading and film formation of organic polymer solutions on liquid surfaces are key processes in coating, printing, and interfacial processing. However, the mechanisms by which aqueous polymers regulate spreading kinetics and film morphology are not yet fully understood. In this study, the free spreading of Poly(3-hexylthiophene-2,5-diyl) (P3HT)/chlorobenzene solution on poly(vinyl alcohol) (PVA) aqueous surface was employed as a model system to investigate how PVA concentration, molecular weight, degree of hydrolysis, and temperature collectively govern spreading behavior and film formation. Video recording was used to monitor the evolution of the spreading and front-edge morphology, while step-profilometry, UV–visible absorption spectroscopy, and atomic force microscopy were employed to characterize the resulting films in terms of thickness distribution, optical uniformity, and surface roughness. The results reveal that PVA can significantly regulate both the spreading kinetics of P3HT/chlorobenzene droplets and the final film morphology. PVA concentration exhibited a non-monotonic effect on spreading behavior, with intermediate concentrations favoring larger spreading areas and more continuous films. Increasing the PVA molecular weight altered the concentration-dependent spreading window and enhanced asymmetry at the spreading front, whereas reducing the degree of hydrolysis decreased interfacial tension and thereby increased the thermodynamic driving force for spreading, yet the actual spreading rate remained constrained by molecular diffusion, interfacial adsorption, and chain-segment rearrangement. Temperature and a saturated chlorobenzene vapor atmosphere further modulated the interplay among solvent evaporation, interfacial driving force, and viscous dissipation. Under optimized conditions, the resulting P3HT films displayed uniform thickness profiles, consistent optical absorption, and nanoscale surface roughness, and could be repeatedly transferred, assembled into well-defined multilayer structures, and printed onto flexible and curved substrates. These findings demonstrate that PVA aqueous subphase provides a tunable low-shear route for transferable P3HT thin-film fabrication and suggests its potential applicability to other polymer film-forming systems.

Polymers doi: 10.3390/polym18131673

Authors: Youyun Zou Yi Liu Xin Zha Ang Wang Zongrong Wang Jin Qian

Insufficient interfacial interaction between nanoconductive materials and polymer matrices severely limits the mechanical, electrical, and pressure-sensing properties. Carbon nanotubes (CNTs), widely used as polymer reinforcements due to their excellent properties, can significantly enhance the mechanical performance of nanocomposites by improving the interfacial interactions with the matrix. Given the diversity of functionalized CNTs, a systematic study of their interfacial bonding mechanisms is of great importance for both scientific research and engineering applications. To this end, this study employs molecular dynamics simulations to investigate the interfacial characteristics and mechanical responses of functionalized CNT/polyimide (PI) systems. The results demonstrate that functionalization treatments significantly enhance both the interfacial interaction and the shear performance of CNT/PI nanocomposites. Specifically, the interfacial shear strength of the carboxylated CNT/PI composite reaches 269.83 MPa, representing a 20% improvement; furthermore, this property further increases with higher functional group content. This work elucidates the influence of functional group type and content on the interfacial shear performance of CNT/PI composites at the atomic scale, providing new physical insights.

Polymers doi: 10.3390/polym18131672

Authors: Sogand Ghafari Movahed Iman Rezvani Ali Dorieh Saeed Kamrani Meysam Mehdinia Mohammadreza Pourpilehkesh Mohammad Hassan Shahavi Sara Nabipoor Petar Antov Viktor Savov Viktoria Dudeva Widya Fatriasari Lee Seng Hua Antonio Pizzi

Biobased wood adhesives are essential to reducing the dependence of wood-based panels on petrochemical and formaldehyde-emitting resins. This review critically synthesizes recent progress in lignin-, tannin-, starch-, furan/HMF-, organic acid-, and soy protein-based adhesive systems, with emphasis on chemical reactivity, curing mechanisms, water resistance, processability, and industrial relevance. The discussion distinguishes laboratory performance from industrial feasibility by considering specific press time, solids content, viscosity, raw material variability, emissions, cost, life-cycle performance, and compatibility with particleboard, medium-density fibreboard, plywood, and related engineered wood products. Lignin and tannins are highlighted as the most chemically compatible phenolic platforms, starch and soy systems as abundant but moisture-sensitive binders requiring targeted crosslinking, HMF and furan derivatives as promising aldehyde-type formaldehyde-free crosslinkers, and citric acid systems as attractive polyester-forming binders with pressing-temperature limitations. The review concludes that near-term adoption will most likely proceed through hybrid and partially biobased systems, whereas fully biobased adhesives require faster curing, standardized feedstocks, pilot-scale validation, and transparent techno-economic and life-cycle assessment.

Polymers doi: 10.3390/polym18131671

Authors: Yirui Shen Xiaomei Wang Yangyang Xiong Xinmeng He Pingping Jiang Guizhen Xing

Dioctyl adipate (DOA) and dioctyl sebacate (DOS) are widely used cold-resistance plasticizers; however, their low molecular weight and weak polarity result in poor thermal stability and migration resistance. Here, we report the synthesis and performance of bio-based cold-resistance plasticizers derived from trans-aconitic acid with enhanced migration resistance. Tri-n-butyl trans-aconitate (TBTA), tri-n-hexyl trans-aconitate (THTA), and tri-n-octyl trans-aconitate (TOTA) were synthesized via one-step esterification with aliphatic alcohols and applied in poly(vinyl chloride) (PVC). Compared with commercial plasticizers di-(2-ethylhexyl) phthalate (DEHP), tributyl citrate (TBC) and DOA, the synthesized plasticizers demonstrated excellent thermal stability and cold-resistance. After freezing treatment, the Tg values of TBTA/PVC (18.99 °C) and THTA/PVC (20.88 °C) were lower than those of DEHP/PVC (22.74 °C). The branched architecture was supposed to strengthen interactions between plasticizers and PVC, improving volatility resistance and solvent extraction resistance. Compared with DOA/PVC at 48 h, TBTA/PVC, THTA/PVC and TOTA/PVC displayed volatility mass loss reduction of ~1.5%, 4% and 7%, respectively. Their extraction mass loss in ethanol decreased by 5–6%, while in petroleum ether, TBTA/PVC and TOTA/PVC dropped by 11.95% and 2.63%, respectively. These bio-based plasticizers are promising alternatives to the poor migration resistance of conventional low-temperature plasticizers.

Polymers doi: 10.3390/polym18131670

Authors: Joaquín Hernández-Fernández Juan López-Martínez

Maintaining a stable melt flow index (MFI) is a critical objective in industrial polypropylene production because MFI directly reflects polymer molecular weight and strongly influences downstream processing performance. Although the effects of catalyst formulation and hydrogen concentration on polypropylene properties are well established, the operational origins of residual fluctuations in MFI under highly stable industrial conditions remain poorly understood. In this work, the relationships between feedstock quality, process operation, and residual MFI variability were investigated during the production of a commercial polypropylene grade in an industrial gas-phase reactor. A dataset comprising 61 industrial observations was assembled by integrating laboratory quality measurements with operational variables related to hydrogen concentration, catalyst management, reactor hydrodynamics, thermal behavior, productivity, and fouling. In parallel, the concentrations of key catalyst inhibitors, including carbon oxides, sulfur compounds, water, oxygen, acetylene, methylacetylene, propadiene, arsine, and phosphine, were quantified before and after the use of a modified zeolite-based purification system. The purification process reduced catalyst poisons to ppb levels, producing polymer-grade propylene with monomer purity exceeding 99.95 wt.%. Under these highly controlled conditions, the production campaign exhibited remarkable quality stability, with an average MFI of 3.03 g/10 min and a coefficient of variation of only 6.63%. Principal component analysis revealed that two dominant operational domains could describe 86.49% of the total process variability. The first domain was associated with reactor hydrodynamics, fouling behavior, and thermal conditions, whereas the second domain was governed by catalyst-system variables and hydrogen-mediated chain-transfer mechanisms. Variable importance in projection analysis identified Plate Fouling Factor (VIP = 2.17), Production Rate (VIP = 1.33), and H2/C3 Ratio (VIP = 1.17) as the variables most strongly associated with residual MFI fluctuations. The results demonstrate that once feedstock-related disturbances are effectively minimized, residual MFI variability arises from interactions among the hydrodynamic, thermal, and catalytic operational domains rather than from a single controlling parameter. These findings provide new insights into process–quality relationships in industrial polypropylene manufacturing and establish a practical framework for identifying the operational origins of subtle fluctuations in polymer quality in highly stabilized production systems.

Polymers doi: 10.3390/polym18131669

Authors: Supanicha Alapol Thidarat Imyen Khemmathin Lueangwattanapong Nutchapon Chiarasumran Maythee Saisriyoot Anusith Thanapimmetha Yi-Shen Huang Chih-Feng Huang Penjit Srinophakun

Wastewater containing heavy metals and dyes poses serious environmental risks. This study developed a multifunctional composite by coating polyurethane foam (PUF) with milled activated carbon (mAC) and a zirconium-based metal–organic framework (Zr-MOF) for the simultaneous removal of hexavalent chromium (Cr(VI)) and Congo red (CR). The composite was synthesized using a hydrothermal method to grow Zr-MOF on the surface. The SEM analysis confirmed the successful incorporation of mAC and surface modification with Zr-MOF, which resulted in increased surface roughness and porous morphology. XRD and FTIR confirmed the presence of organic ligands connected to the metal structure and the functional groups of each component in composite materials. The optimum conditions for Zr-MOF/mAC/PUF adsorption (nearly 100% removal) in the binary Cr(VI)/CR solution (50 mg/L each) were 25 °C, pH 9, and 150 rpm for 24 h. The Zr-MOF/mAC/PUF was hydrophilic with a swelling ratio of 2.64 g/g. The thermodynamic investigation of Zr-MOF/mAC/PUF resulted in 141.6218 kJ/mol for Cr(VI) and 166.111 kJ/mol for CR of ΔH° (rapid adsorption), negative ΔG° (spontaneous adsorption), a high positive value of ΔS° (disorder structure) and low activation energy (approximately 2.5 to 2.8 kJ/mol). After analyzing the isotherm and reaction kinetics, the possible mechanism could be endothermic physicochemical adsorption and pseudo-second-order kinetic behavior, with electrostatic attraction and diffusion control. The study of 6-times-reused Zr-MOF/mAC/PUF adsorption identified as a decrease of 7.55 percentage point without changing notable morphology and functional groups, based on SEM and FTIR.

Polymers doi: 10.3390/polym18131668

Authors: Sergei L. Shmakov Natalia N. Pozdnyakova Oksana V. Tkachenko Anna B. Shipovskaya

Nanoparticles of the aminopolysaccharide chitosan (ChNPs) are effective delivery platforms for biologically active substances for agrobiotechnological applications and hold great promise for solving precision problems in sustainable and efficient agriculture. This review presents an analysis of research publications during the past 20 years examining methods for producing ChNPs through ionotropic gelation using sodium tripolyphosphate for cross-linking macrochains, which are of practical interest for agriculture. Key aspects of the nanostructure formation process are analyzed, including the influence of the physicochemical characteristics of the aminopolysaccharide, the concentration and ratio of reagents, and ionic cross-linking conditions on the average size, size distribution (polydispersity), and zeta potential of nanoparticles. Particular attention is paid to several approaches proposed in the literature for determining optimal gelation conditions to obtain ChNPs with pre-specified size characteristics. Potential applications of nanostructured preparations based on these nanoparticles for agrobiochemical purposes are considered, including the encapsulation of antifungal, antiviral and antimicrobial agents, pesticides, NPK fertilizers, metal ions, plant extracts, essential oils, etc., to develop biodegradable stimulants for seed germination and plant growth, increased crop yields, and improved agricultural product quality. It is concluded that blocking the protonated amino groups of chitosan with tripolyphosphate anions is undesirable due to the reduced biological activity of the macromolecules and the nanostructured preparations obtained therefrom. An alternative approach for producing ChNPs with high biological activity with neither use of cross-linking agents nor encapsulation of agrochemicals is described.

Polymers doi: 10.3390/polym18131667

Authors: Pedro Valentín Badía-Hernández Rocío Díaz-Puertas Paula del Carmen Sánchez-García Alberto Falcó Pilar García-Morales Ricardo Mallavia

Poly(methyl vinyl ether-alt-maleic anhydride) (PMVEMA) is a versatile synthetic copolymer that has gained considerable attention in biomedical and pharmaceutical applications due to its biocompatibility, biodegradability, bioadhesive properties and chemical reactivity. This review summarizes the current knowledge regarding the derivatives, physicochemical properties, functionalization and crosslinking strategies of PMVEMA, with particular emphasis on their relevance to biomedical applications. A comprehensive literature analysis was performed using major scientific databases, combined with artificial intelligence-assisted text mining, to identify the principal research trends associated with PMVEMA. The reviewed studies demonstrate that the reactive anhydride groups of PMVEMA enable the formation of a wide variety of derivatives, including hydrogels, nanoparticles and nanofibers with tunable properties. These characteristics have facilitated its application in different fields, including immunology, drug delivery, dentistry and dermatology. In particular, PMVEMA-based systems exhibit enhanced mucosal adhesion, controlled drug release, immunoadjuvant activity and biocompatibility in vitro and in vivo. Despite its broad applicability, further studies are still needed to fully elucidate its biodegradation mechanisms in vivo and optimize its clinical translation.

Polymers doi: 10.3390/polym18131666

Authors: Chi-Hsuan Su Selveraj Nagarajan Chean-Cheng Su Eamor M. Woo

Through microscopy analyses onto 3D-dissected interiors of crystallized poly(ethylene adipate) (PEA) at isothermal 28 °C temperatures that are known to pack with double ring-banded spherulites, complete surface-relief patterns correlating with interior periodic assembly profiles on mechanisms are obtained. Top-surface-relief ridge bands exhibit different width caused by slant angles between the interior radially orientated lamellae with respect to the top surface. The detailed interior structures gained from analyses on the dissected PEA spherulites yield critical correlations between the interior assembly and topology banding patterns, leading to a clue that analyses cannot be restricted to simply just on the top-surface-relief patterns. With advanced dissection techniques, 3D views on bulk interiors have offered dramatic breakthrough views and led to unique clarity in assembly mechanisms of periodic crystal aggregation.

Polymers doi: 10.3390/polym18131665

Authors: Nello Russo Federica Recupido Loredana Tammaro Maria Oliviero Barbara Liguori Roberta Marzella Letizia Verdolotti Giuseppe Cesare Lama

The food packaging sector widely relies on polymeric materials, and as sustainability concerns grow, commodity polymers need to be replaced with innovative and more sustainable materials. Thermoplastic polyurethane (TPU) is a versatile elastomeric polymer characterized by flexibility, strength, chemical and abrasion resistance, and biocompatibility. However, it presents some limitations, notably in terms of functional properties (i.e., barrier properties). The use of nano-sized renewable fillers, such as cellulose nanocrystals (CNCs), may improve these properties, extending the applicability range of TPU. In this work, bio-based TPU nanocomposites were obtained by adding commercial silane-modified cellulose nanocrystals (Si−O−CNC) at different contents (1–5 wt.%). The nanocomposites were produced via melt mixing followed by compression molding and were characterized in terms of chemical (FTIR), morphological, thermal, mechanical, rheological, wettability, and barrier properties (i.e., water vapor permeability, WVP and oxygen transmission rate, OTR). The presence of Si−O−CNC promoted hydrogen bonding interactions with the TPU matrix, affecting the microphase separation and organization of the hard segments. These microstructural changes improved thermal stability, reduced WVP and OTR, and increased tensile properties at lower nanofiller contents (1–3 wt.%). At higher contents, partial nanofiller aggregation was observed, leading to a reduction in mechanical performance. Overall, these results suggest that TPU/Si−O−CNC nanocomposites have promising potential as sustainable food packaging materials.

Polymers doi: 10.3390/polym18131664

Authors: Ray Tahir Mushtaq Ghulam Hassan Askari Mudassar Rehman Rakan Albarakati Yanen Wang Aqib Mashood Khan

Triply periodic minimal surface (TPMS) gyroid lattices are promising lightweight and energy-absorbing polymer structures, but their manufacturability by material extrusion (MEX) depends strongly on cell size, grading direction, and relative density. This study investigates PLA gyroid lattices with uniform and graded cell-size configurations using initial and final cell sizes of 1, 1.5, and 2 mm and target relative densities of 10, 20, and 30%. A full-factorial design was used to construct a printability map, followed by quasi-static compression testing, areal surface-roughness characterization, and SEM observation of representative specimens. The printability results showed that low-density fine-cell configurations were most prone to incomplete wall formation and collapse, whereas the 30% relative-density group was printable for all investigated cell-size combinations. Under compression, the 30% relative-density uniform 1 mm gyroid showed the highest maximum stress among the tested configurations, while graded structures terminating in smaller cells also provided favorable load bearing and energy-absorption behavior. The plateau stability index, calculated from stress fluctuations between collapse and densification, helped distinguish stable progressive collapse from more oscillatory deformation. Surface roughness and SEM observations further indicated that smoother, more continuous wall surfaces were associated with more uniform deformation, whereas rougher and defect-rich surfaces promoted localized buckling, cracking, and brittle collapse. Overall, the results identify experimentally supported relationships between gyroid cell-size configuration, printability, surface integrity, and compressive response within the investigated PLA MEX design space.

Polymers doi: 10.3390/polym18131663

Authors: Jiang Li Fulun Peng Jianzhao Zhao Xinliang Chai Junjie Fu Shaoying Li Xujiang Chao

Powder Bed Fusion-Laser Beam/Polymer (PBF-LB/P) is a key additive manufacturing technology widely used in aerospace, but its process parameters are difficult to optimize for thermoplastic composites due to poor powder flowability and unstable melting regions. To address this challenge, this paper develops discrete element and finite element models to systematically determine the PBF process window for both powder spreading and sintering stages, with verified reliability. In the spreading stage, the powder layer performance is evaluated through surface profile, density, and uniformity. The effects of reinforcement phase, spreading speed, and layer thickness are analyzed, establishing reasonable spreading parameter windows. It is found that the optimal layer thickness for PEEK powder is determined to be 0.13 mm, while that for PEEK/CF composite powder is 0.12 mm. At the optimal layer thickness, the powder bed exhibits desirable properties, which minimize its adverse influence on the sintering process and serve as a prerequisite for subsequently establishing the sintering process window. For the sintering stage, sufficient sintering constraint criteria are established, and a systematic determination method is proposed. By analyzing microscopic sintering mechanisms and characterizing the effects of laser power, scanning speed, and hatching space on melt pool dimensions and temperature, a reasonable sintering process window can be efficiently determined. It is found that within the process window, the PEEK specimens achieved a maximum relative density of 99.31% and exhibited a tensile strength 13.1% higher than that of specimens processed outside the window, demonstrating a clear superiority.

Polymers doi: 10.3390/polym18131662

Authors: Haitao Hu Hailiang Dong Mingpeng He Boxin Ma Yanli Liu Junguo Gao

The concentration of electric fields at the end region of stator bars in large generators can readily induce corona discharge. Under long-term operation, corona discharge may cause drift in the surface conductivity and nonlinear coefficient of anti-corona materials, thereby weakening their capability to homogenize the tangential electric field. In severe cases, this can lead to charring failure of the anti-corona material. To improve the electrical-parameter stability and surface morphological resistance to corona aging of silicon carbide (SiC)-based anti-corona materials under long-term corona exposure, epoxy-resin-based anti-corona materials were investigated in this study. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were first employed to analyze the effects of corona aging on the microstructure and chemical structure of the anti-corona layer, thereby revealing its failure mechanism. Subsequently, the evolution of surface conductivity, nonlinear coefficient, and surface morphology of bisphenol A epoxy resin (EP)- and hydrogenated bisphenol A epoxy resin (H-EP)-based anti-corona materials during 120 h of corona aging was comparatively investigated. On this basis, different mass fractions of organically modified montmorillonite (OMMT) were introduced into the H-EP-based anti-corona material for synergistic modification. The OMMT used in this study had a particle size of approximately 5 μm and an interlayer spacing of 2.6 nm, and its lamellar morphology and dispersion state in the epoxy matrix were characterized by cross-sectional SEM. Meanwhile, the trap-regulation mechanism of the OMMT-modified anti-corona materials was analyzed using isothermal surface potential decay (ISPD). The results show that erosion of the epoxy resin matrix by corona discharge is the primary cause of internal conductive-pathway disruption and anti-corona layer failure. Compared with the EP-based material, the H-EP-based material exhibited better conductivity and nonlinear stability during aging, although a certain degree of drift still occurred. The incorporation of an appropriate amount of OMMT further improved the corona resistance of the material. Among the investigated samples, the material containing 1 wt% OMMT showed the best performance, with its conductivity stabilized within the range of 10−13–10−11 S, the lowest variation rate of 104.76%, a relatively stable nonlinear coefficient, and slight surface damage. The ISPD results indicate that the interfaces introduced by OMMT increase the deep-trap density and suppress carrier migration, thereby stabilizing the conductive network. Overall, the synergistic effect of the H-EP matrix and 1 wt% OMMT can effectively enhance the corona resistance of SiC-based anti-corona materials.

Polymers doi: 10.3390/polym18131661

Authors: Alexandru Constantin Stanciu Anton Hadăr Nicolae Goga Mihai-Constantin Butolo Florin Baciu Stefan-Dan Pastrama Daniel Vlăsceanu

In this paper, a machine learning model to predict the Young’s modulus of polylactic acid specimens manufactured by Fused Deposition Modeling is proposed, based on a stacked ensemble architecture. The model uses as input parameters the fill degree, printing speed, filling pattern, yield strength, and tensile strength, along with additional features obtained through feature engineering. The proposed approach integrates nine base models with a linear meta-model, allowing it to capture both linear and nonlinear relationships between the variables. The results obtained on the test dataset show strong predictive performance, with a Mean Squared Error with a value of 7.31 together with a Coefficient of Determination R2 with a value of 0.99, which is noticeably better than the performance of the individual models. To validate the model, a separate group of specimens was tested, and the difference between the measured and predicted Young’s modulus was about 1% on average. The model was also implemented in a desktop application with a graphical interface, in which the calculation can be run directly, thus allowing a rapid estimation of Young’s modulus. In this way, the need for laborious experimental testing is reduced with the help of AI-based approaches in additive manufacturing.

Polymers doi: 10.3390/polym18131660

Authors: Kai Rist Iris Lamparth Sadini Omeragic Lauren Geurds Benjamin Grob Yohann Catel

The development of 3D printing high-impact denture bases is challenging, as materials exhibiting both high flexural strength/modulus and fracture toughness are required. Nowadays, most of the commercially available 3D printing denture bases contain significant amounts of crosslinking monomers and therefore behave as brittle materials. In this contribution, urethane dimethacrylate DMA1/(octahydro-4,7-methano-1H-indenyl)methyl acrylate (OMIMA) 1/1 (wt/wt) formulations containing a poly(ε-caprolactone)-polydimethylsiloxane-poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymer (BCP1) and fumed silica SiO2-NPs were evaluated for DLP 3D printing of fracture-tough denture bases. The post-curing step was performed at various temperatures (RT, 60 °C, 80 °C, 100 °C and 120 °C). This parameter was shown to strongly influence the Tg and mechanical properties of 3D printed materials. A post-curing temperature of 100 °C was found to be ideal. Under these conditions, 3D printed materials exhibiting excellent mechanical properties were successfully obtained. Furthermore, the amounts of BCP1 and SiO2-NPs were varied. The formulation containing 8.0 wt% of BCP1 and 10.0 wt% of SiO2-NPs (FS = 67.5 ± 1.3 MPa, FM = 2450 ± 71 MPa, Kmax = 2.11 ± 0.06 MPa m1/2, Wf = 1109 ± 19 J m−2) was able to fulfill the ISO 20795-1:2013 requirements in terms of flexural strength (FS)/modulus (FM) and fracture toughness for denture bases with improved impact resistance (FS > 65 MPa, FM > 2000 MPa, Kmax > 1.9 MPa m1/2, Wf > 900 J m−2). This material showed better performance than the commercially available formulations Printodent® GR-14.2 denture HI (FS = 69.2 ± 1.8 MPa, FM = 2153 ± 76 MPa, Kmax = 0.82 ± 0.04 MPa m1/2, Wf = 79 ± 10 J m−2) and Lucitone Digital PrintTM 3D denture base (FS = 56.7 ± 1.9 MPa, FM = 2144 ± 12 MPa, Kmax = 1.92 ± 0.09 MPa m1/2, Wf = 1272 ± 177 J m−2).

Polymers doi: 10.3390/polym18131659

Authors: María Guadalupe Morán-Aguilar Iván Costa-Trigo José Manuel Domínguez Fabiola Vilaseca

The transition toward renewable and environmentally responsible materials has intensified interest in cellulose-based systems for use in sustainable packaging applications. Although cellulose offers biocompatibility, structural versatility, and tuneable physicochemical properties, conventional modification routes rely on harsh chemicals and generate environmentally burdensome effluents. In this study, an efficient and a potentially green strategy for cellulose modification was developed using acid-based deep eutectic solvents (DES) composed of choline chloride and lactic, acetic, or citric acid at different molar ratios. Under mild conditions (110 °C, 4 h), DES pretreatment reduced glucan content in sulphite pulp from 99% to 79–93%, depending on the hydrogen bond donor (HBD), while suggesting an apparent increase in relative crystallinity, from approximately 82% to 90%, as estimated by the Segal method. FTIR, XRD, and morphological analyses revealed the disruption of the hydrogen bonding network, enhanced fibrillation, and residual DES-derived functional groups detectable by FTIR. Although DES pretreatment increased structural order, it also reduced enzymatic digestibility due to the higher proportion of crystalline domains. Overall, the results demonstrate that acidic DES constitutes a sustainable and recyclable medium capable of modulating cellulose structure and generating materials with enhanced physicochemical properties. These findings suggest that DES-modified cellulose could serve as a potential reinforcement platform for future biodegradable packaging and bioplastic formulations, enabling the development of high-performance, renewable, and environmentally compliant packaging materials.

Polymers doi: 10.3390/polym18131658

Authors: Tetsuo Takayama Koki Tsuchiya Akito Endo

For the impact-resistance evaluation of thermoplastics, the DuPont impact test is widely used to replicate multiaxial stress states inherent in actual product environments. However, conventional evaluation methods remain constrained by probabilistic pass/fail judgments or empirical calculations of absorbed energy. Consequently, quantifying the “material-specific fracture criterion,” which is indispensable for high-fidelity computer-aided engineering (CAE) analysis, persists as an important challenge. While our previous works established the derivation of CES from uniaxial tensile tests, the core originality of this study lies in extending this mechanical framework to the dynamic and multiaxial stress states of the DuPont impact test. By integrating a mathematical model with the probabilistic results of the staircase method, we enable for the first time the quantitative identification of material-specific fracture thresholds directly from standard drop-weight impact configurations. For this study, a novel mechanical model for deformation and fracture behavior in the DuPont impact test is constructed. Then a quantitative evaluation method is proposed for the “Critical Expansion Stress (CES),” a material-specific threshold triggering fracture under multiaxial stress. Specifically, using thermoplastic materials of five types and seven grades (including PP, POM, PS, ABS, and PC), the surface impact energy absorbed per unit volume was calculated via the DuPont impact test using the staircase method, accounting for size effects. Furthermore, microscopic parameters (shear modulus G and critical void volume fraction f0) were identified theoretically based on the mechanical properties obtained from short-beam shear tests. These parameters were integrated into a mathematical model to derive the CES. Comparing the derived CES with the true-stress-based uniaxial tensile strength, which incorporates the necking behavior during large deformations, revealed a distinct correlation governed by their mechanical relation (the 1:3 rule) based on the theoretical definition of hydrostatic stress. For the highly ductile polymer exhibiting significant strain hardening, this correlation holds universally when evaluated at the initial plastic flow stage prior to massive molecular orientation. The proposed method serves as a practical quantitative screening tool for evaluating the surface impact characteristics of plastic materials, providing an accessible framework for identifying material-specific fracture thresholds.

Polymers doi: 10.3390/polym18131657

Authors: Khalifa Salem Gallouz Shaban Ismael Albrka Ali Amina B. Abubakar Faridah Hanim Khairuddin Munder Bilema Nasradeen Ali Khalifa Mustafa Alas

The effects of weather conditions on modified asphalt mixtures were investigated in this study. Acrylonitrile Styrene Acrylate (ASA) polymer was used as a modifier with concentrations of 3, 5, and 7%. The viscosity test was performed to determine the blending and compaction temperatures for the base and modified mixtures, while Field Emission Scanning Electron Microscopy (FE-SEM) was utilized to explore the dispersion of the polymer in the asphalt binder matrix. Moreover, mechanical tests were applied to observe the changes in the modified asphalt binders. The highest improvements were obtained for a 5% ASA concentration. The resilient modulus increased by 78%, while resistance to dynamic creep improved by 74% compared with the base asphalt mixture. The wheel tracking and moisture susceptibility results further illustrated that the modified asphalt mixtures were less susceptible to moisture than the base asphalt mixture. The aging index results showed that the modifier can mitigate the effects of weather conditions, and the 5% ASA showed the best performance among the mixtures.

Polymers doi: 10.3390/polym18131656

Authors: Sarai Agustin Salazar Paolo Maria Riccobene Sabrina Carola Carroccio Fabiana Convertino Antonis Mistriotis Christina Pyromali Andrea Antonino Scamporrino Evelia Schettini Giuliano Vox Pierfrancesco Cerruti

This study evaluates the performance of major types of conventional and bio-based plastic items commonly used in agriculture to provide comprehensive insights into their key structural and functional properties, including the chemical composition of the polymer matrix and additives, mechanical behavior, and thermal and radiometric properties. Twelve agricultural plastic (AP) items were analyzed: covering mulch films, geotextile ground cover, protection fleece and low tunnel fleece cover, fertilizer sack, fly trap, irrigation pipe, tree binding net, guide for tree, silage film and hay bales protection fabric. This selection of APs also encompasses a broad range of basic polymers, including conventional materials (mainly polyethylene and polypropylene) and bio-based formulations (primarily starch- or lignocellulose-containing blends). Mass spectrometry and infrared spectroscopy analyses were performed to assess polymer composition and additives. Mechanical properties were assessed through tensile and puncture tests; in addition, radiometric, thermogravimetric, surface wettability, water absorption and permeability tests were also performed to assess other relevant physical characteristics. The study identified significant differences among bio-based biodegradable APs and compared them with their conventional polyolefin-based counterparts. Material composition and structure were found to critically influence water interactions, shaping the balance between durability, degradation, and crop protection performance. Notably, bio-based mulch films exhibited higher water vapor permeability (0.6–1.1 × 10−13 g/m Pa s), reduced penetration resistance (12.1 N) and lowered impact and tensile strengths (21.8 MPa). Water interaction tests showed that the starch-based mulch film displayed very high swelling (above 100%), favoring biodegradation, whereas a biodegradable blend based on polyhydroxybutyrate and polybutylene succinate exhibited minimal swelling (<3%). Material composition and morphology were also key determinants of water vapor transport: dense polymer films provided superior moisture barriers (permeability range 0.013–0.04 × 10−13 g/m Pa s), while fibrous or biodegradable materials allowed enhanced vapor permeability. The results of this study, highlighting functionality, advantages and limitations of biodegradable APs versus conventional APs, are intended to guide future innovation in AP design, ensuring alignment with both the operational demands of modern agriculture and environmental sustainability goals. The data obtained from this study can support scientific advancements and policy recommendations on the use and management of plastics in agriculture.

Polymers doi: 10.3390/polym18131655

Authors: Nuttapong Khiaonoi Kwanchai Kraitong Punyawan Lumpaopong Jarupa Viyoch

Andrographolide-loaded microparticles with an aqueous-based carrier system were developed with the aim of pulmonary drug delivery. Five formulations of andrographolide (0.6–5.8% w/w) loaded on mixed-polymer carriers containing chitosan (CHS), hydroxyethyl cellulose (HEC), Poloxamer 188, and PEG 20,000, with various ratios were produced under various spray-drying parameters: solution viscosity (5–20 cP), atomization air pressure (0.8–1.5 bar) and solution feed rate (3–6 mL/min). The physiochemical properties of the microparticles were strongly affected by carrier composition and atomization air pressure. The optimal formulation: andrographolide 0.6% w/w, CHS 62.2% w/w, HEC 15.5% w/w and Poloxamer 188 21.7% w/w, spray dried using solution viscosity 15 cP, atomization air pressure 1.1 bar and feed rate 3 mL/min, was selected according to its particle sizes (3–5 µm) with rough morphology, encapsulation efficiency (54.47%) and release behaviors (22.31%/h and 89.23% within 4 h). Good physical, chemical, and thermal stabilities under room storage condition (28 ± 2 °C, 50% relative humidity) were also proven. Importantly, it demonstrated potent antiviral activity against Influenza A/H1N1, achieving a 3.3-log10 reduction in viral titer with 99.95% inhibition. Overall, this aqueous-based carrier approach and spray-drying technique offer a stable and effective inhalable formulation for localized treatment of influenza infections.

Polymers doi: 10.3390/polym18131654

Authors: Zhiwei Yin Limin Zhang Rui Shi Xin Xia Zhaoxin Wang Ling Li Zhuo Chen

Cell therapies for gastric disorders lack minimally invasive delivery platforms that preserve cell viability during storage and enable effective tissue penetration, owing to the high toughness and harsh environment of the gastric wall. Herein, we developed a mechanically reinforced, porous silk-based cryogenic microneedle (silk-cryoMN) platform for in situ cell delivery to the gastric wall. The optimized 1.5% (w/v) silk scaffolds exhibited interconnected pores (24.4 ± 7.9 μm, ~81% porosity), a compressive strength (422.8 ± 73.4 MPa), and a 3.4-fold increase in β-sheet content. The silk-cryoMNs showed greater thermal stability than H2O-cryoMNs, maintaining structural integrity for over 60 s at room temperature. With a cryopreservation medium containing 100 mM sucrose and 2% DMSO, post-thaw cell viability exceeded 80% after 11 days of freezing, and most cells were released within 1 h. Furthermore, ex vivo studies confirmed penetration of porcine gastric tissue to depths of 422–448 μm within 30 s. These results suggest that the platform may address several translational barriers, including tissue penetration, handling stability, and cell viability preservation. Further in vivo studies and long-term safety evaluations are needed before clinical translation can be considered.

Polymers doi: 10.3390/polym18131653

Authors: Vera V. Budaeva Anna A. Korchagina Yulia A. Gismatulina Evgenia K. Gladysheva Polina A. Gorbatova Anastasia A. Zenkova Vladimir N. Zolotukhin Gennady V. Sakovich

This paper reports new results on the synthesis and comparative characterization of cellulose nitrates (CNs) derived from Miscanthus × giganteus stems and from commercial microcrystalline cellulose (MCC). Miscanthus CNs synthesized by nitration with mixed sulfuric–nitric acids containing 16–20% water exhibit new functional properties: a high solubility in organic solvents (100% in acetone and 97–99% in alcohol–ether solvent) and a high viscosity (17–51 mPa·s), with a nitrogen content of 10.54–12.08 wt%. CNs from Miscanthus × giganteus are similar in nitrogen content and solubility to those from MCC (11.54% and 99%) but have a significantly greater viscosity (3 mPa·s), which is an undoubted advantage and considerably expands their potential application range. The solubility test of CNs synthesized from both sources demonstrated that Miscanthus CNs have a better film-forming ability. SEM analysis revealed a great difference in fiber length, despite the same cylindrical shape and observed aggregation: 1.0–2.0 mm for CNs from Miscanthus versus 40–60 μm for CNs from MCC. IR spectra of CNs from both sources showed the appearance of five new characteristic frequencies (1632–1633, 1273–1274, 823–826, 748, 677–686 cm–1 for Miscanthus CNs and 1659, 1277, 832, 747, 691 cm–1 for CNs from MCC), allowing the obtained compounds to be identified as nitric acid esters of cellulose. According to TGA/DTA analysis, the synthesized polymers have similarly high values of the onset temperature of both intense decomposition (197–198 °C) and narrow exothermic peaks (209–211 °C and 212 °C), respectively, indicating their high thermal stability. The combination of high solubility, viscosity, thermal stability and chemical purity of CNs derived from Miscanthus × giganteus stems suggests that strong thin films can be obtained and recommended for use in the manufacture of nitrocellulose membranes.

Polymers doi: 10.3390/polym18131652

Authors: Musiliu A. Liadi Tawakalt O. Ayodele Ibrahim A. Bello C. Igathinathane Hammed M. Ademola

Mycelium-bound composites (MBCs) have emerged as a promising class of biofabricated materials that integrate fungal hyphal networks with lignocellulosic substrates to form lightweight, biodegradable structures without synthetic adhesives. Despite rapid growth in the field, the current literature remains fragmented, with inconsistent methodologies and widely varying reported material properties. This review advances the field by moving beyond descriptive synthesis toward a quantitative and conceptual integration of existing studies. We systematically analyze how key fabrication variables—including fungal species, substrate composition, growth conditions, and post-processing parameters—govern density, porosity, and mechanical performance. A process–structure–property (PSP) framework is proposed to combine these relationships and explain discrepancies across studies. We highlight the dominant role of densification and moisture conditioning in determining compressive strength, often outweighing species-level effects. A comparative synthesis of reported data reveals significant variability in compressive strength (0.05–1.2 MPa) and elastic modulus, attributable to inconsistencies in sample preparation, testing protocols, and environmental conditioning. To address this, we identify critical gaps in standardization and propose actionable testing protocols and reporting guidelines for reproducibility. Furthermore, we assess the technology readiness level (TRL) of MBC systems and distinguish between laboratory-scale innovations and commercially viable processes. While hybridization strategies and biofunctional applications offer promising avenues, their maturity varies widely. This work provides a decision-oriented framework for MBC design and a roadmap for transitioning these materials from experimental systems to scalable, standardized, and application-ready biomaterials.

Polymers doi: 10.3390/polym18131651

Authors: Maksim Nikonovich Amilcar Ramalho Nazanin Emami

Cryogenic environments impose severe thermal and mechanical stresses on polymer components, yet the effects of long-term cryogenic cycling on their subsequent room-temperature performance remain insufficiently understood. This study investigated the influence of cryogenic cyclic aging on the mechanical and tribological behaviour of polyimide (PI)-based materials, including neat PI and composites reinforced with MoS2, graphite, and/or PTFE. Repeated cryogenic cycling was followed by mechanical characterisation and tribological testing at 25 °C in air and vacuum. This work systematically compares neat and filled PI materials after cryogenic cyclic aging and correlates mechanical changes with transfer-film formation and wear behaviour. Cryogenic cyclic aging had only minor effects on weight and thermal stability but significantly altered the viscoelastic behaviour, increasing creep and residual strain, with variations depending on the polymer structure and filler content. Fracture toughness showed a statistically significant improvement only for PI2 (up to 93%). Changes in PI1, PI3, PI4, and PI5 fell within the experimental scatter and were interpreted as non-significant trends. In air, abrasive wear dominated in unreinforced PI, while graphite/PI composites exhibited adhesive wear and improved transfer film formation, reducing wear rates by up to 26%. In vacuum, the wear rate of aged graphite/PI increased by up to two orders of magnitude.

Polymers doi: 10.3390/polym18131649

Authors: Cristóbal Donoso Isidora Reyes-González Katherine Sossa Fernández Javier Coronil Pablo Reyes-Contreras Isabel Carrillo-Varela Benjamín Opazo Rodrigo Hasbún Regis Teixeira Mendonҫa

Cellulose and chitosan are biopolymers widely used to prepare composites due to their complementary charges and intrinsic biocompatibility. While they are mainly of interest for medical applications, they are also suitable for water remediation. In their native states both biopolymers are non-porous; however, after dissolution and subsequent regeneration they can form porous structures that are better suited for such applications. In this work, cellulose pulp and chitosan were dissolved in an ionic liquid and regenerated in water at different mass ratios to produce hydrogels and their corresponding aerogels. The materials were structurally characterized and evaluated for dye adsorption and antimicrobial performance. Methylene blue and Congo red were selected as cationic and anionic dyes, respectively. The concentrations went from 5 to 80 mg/L in 24 h batch adsorption experiments. Chitosan-rich and intermediate cellulose–chitosan hydrogels preferentially removed Congo red, reaching 27 ± 1 mg/g and 24 ± 1 mg/g at 80 mg/L, respectively; the fully cellulose hydrogel maximized methylene blue uptake, achieving 23 ± 1 mg/g under the same conditions. SEM and XRD analyses revealed a hybrid architecture in which chitosan coats cellulose fibers and becomes more amorphous, while cellulose preserves crystalline domains that act as a rigid, highly porous backbone. Aerogels derived from freeze-dried hydrogels exhibited high porosity and water uptake, together with broad-spectrum antimicrobial activity, achieving bactericidal levels (≥99.9% inhibition) against Staphylococcus aureus for all compositions and against Escherichia coli for selected cellulose–chitosan ratios. These results demonstrate that cellulose–chitosan hydrogels and aerogels function as multifunctional bio-based materials whose supramolecular organization, surface charge distribution, and porosity can be tuned to balance adsorption selectivity and antimicrobial performance for advanced environmental applications.

Polymers doi: 10.3390/polym18131650

Authors: Elahe Parvini Abdollah Hajalilou

Gallium (Ga)-based liquid metal (LM) composites, particularly those based on eutectic gallium–indium (EGaIn) and related alloys, have emerged as a promising materials platform for soft and deformable energy storage owing to their unique combination of metallic conductivity, fluidic deformability, and adaptive interfaces. Despite rapid advances in LM-enabled devices, binders remain insufficiently understood and are still commonly regarded as passive structural components. Here, we present a comprehensive binder-centered perspective for LM composites, establishing the binder as a key regulator of electro-chemo-mechanical coupling, interfacial stability, transport behavior, and processability in soft energy systems. We show that tailored binder chemistries in Ga-based LM systems—including stretchable batteries, printable conductors, and soft electrochemical devices—govern LM droplet dispersion, suppress coalescence and leakage, and preserve conductive percolation under large deformation, while enabling room-temperature fabrication and printability through rheological regulation and interfacial wetting. Beyond mechanical confinement, emerging binder functionalities—including dynamic bonding, supramolecular interactions, ionically conductive networks, and reversible polymer architectures—enable self-healing interfaces, adaptive transport pathways, and robust adhesion in deformable devices. By integrating recent advances in stretchable batteries, flexible supercapacitors, printable electronics, and multifunctional soft energy systems, we establish a unified multiscale framework linking binder molecular design to device-level electrochemical and mechanical performance. We further discuss sustainability and manufacturing considerations, including recyclable polymer networks, low-temperature fabrication, and scalable processing strategies. Finally, we outline current challenges and future opportunities toward programmable binder systems with tunable viscoelasticity, interfacial reactivity, and adaptive functionality. This Review establishes binder-centered engineering as a key pathway for transforming LM composites from proof-of-concept materials into resilient, manufacturable, and multifunctional soft energy technologies for wearable, stretchable, and biointegrated electronics.

Polymers doi: 10.3390/polym18131648

Authors: Ghizlane Akhouy Salih Birhanu Ahmed Cemhan Dogan Mehmet Durmus Calisir Manal Zefzoufi Faissal Aziz Nagham Elberishy Yasin Akgul Islam Shyha

Developing biodegradable and functional polymeric materials for active food packaging is essential to mitigate the environmental burden of petroleum-based plastics. In this context, gelatin/chitosan (G–Ch) nanofibrous mats were fabricated via solution blow spinning (SBS) and functionalized with snail slime (SS) and Pinus sylvestris essential oil (PSEO) to enhance their bioactivity and barrier performance. SS is rich in glycoproteins and natural bioactive compounds, while PSEO is characterized by terpene-based antimicrobial and antioxidant activities. SS and PSEO were incorporated into the G–Ch polymeric matrix to enhance the bioactivity, structural functionality and preservation performance of the nanofibrous mats. Three formulations (G–Ch, G–Ch–SS, and G–Ch–SS–10PSEO) were designed to elucidate the influence of snail slime and essential oil incorporation on the structure–property–function relationships of the nanofibrous mats. Morphological analysis revealed a smooth and bead-free fibrous structure across all formulations. The average fiber diameter (AFD) increased from 191.83 nm for G–Ch to 263.88 nm for G–Ch–SS and 295.83 nm for G–Ch–SS–10PSEO. FTIR and XRD analyses showed the physical encapsulation of the active compounds without significant chemical interactions. Furthermore, the incorporation of PSEO increased surface hydrophobicity and reduced air permeability, indicating the formation of a more compact fibrous structure with enhanced barrier properties. The functional performance of the nanofibrous mats was significantly improved by the addition of snail slime and PSEO. The G–Ch–SS–10PSEO formulation exhibited the highest antioxidant activity, reaching 36.8% for DPPH and 42.7% for ABTS, along with enhanced antibacterial efficacy against both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Application tests on chicken wings demonstrated that the bioactive nanofibers effectively suppressed microbial growth, limited pH increases, and reduced lipid oxidation during 14 days of refrigerated storage. Overall, the results demonstrate that the synergistic integration of snail slime and essential oil within a biodegradable polymer matrix provides a promising strategy for designing active nanofibrous materials with enhanced structural and bioactive properties for sustainable food-packaging applications.

Polymers doi: 10.3390/polym18131647

Authors: Zhongqiu Ge Hengfeng Zhu Yiyang Chen Yihang Rong Zhuqun Shi Quanling Yang

Most adsorbent materials typically face difficulties such as poor blood compatibility, weak mechanical strength, and high cost. In this study, oxidized 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was used to obtain cellulose nanofiber (TOCN), and cellulose beads were prepared using a drop curing method. The structure, adsorption properties, and blood compatibility of the prepared beads were thoroughly investigated. The TOCN beads exhibit a uniform, nanometer-scale, three-dimensional porous structure. With increasing carboxyl content, after adsorption of TOCN beads, the bilirubin concentration in rabbit plasma decreased from 0.03 to 0.0089 mg mL−1 within 90 min, which is significantly lower than the average bilirubin concentration in humans (about 0.01 mg mL−1), and the bilirubin concentration decreased by about 70%. The results illustrated the excellent blood compatibility, self-anticoagulant ability, and superior toxin removal capabilities of the TOCN beads, highlighting their potential as an ideal blood purification adsorbent.

Polymers doi: 10.3390/polym18131646

Authors: Flavia Cano Matilde Arese Graziano Brocani Silvia Ponti Gabriele Ciaccio Valentina Brunella

In the context of increasing environmental awareness and the transition toward a circular material economy, the development of sustainable polymeric materials has become a key focus of industrial research. Within this framework, thermoplastic elastomers (TPEs) represent a promising class of materials that combine the elasticity of rubbers with the processability and recyclability of thermoplastics. Their ability to incorporate recycled content further enhances their potential for reducing environmental impact in advanced automotive applications. This study investigates styrenic thermoplastic elastomers (TPS) based on a SEPS (Styrene–Ethylene–Propylene–Styrene) and polypropylene matrix containing over 50% recycled content, with the aim of evaluating the influence of recycled material on structure and performance. TGA, DSC, and ATR-FTIR analyses revealed comparable degradation behavior and similar chemical features between virgin and recycled compounds, while minor differences were possibly related to variations in the plasticizer fraction and polymer-oil interactions. These differences did not significantly compromise the mechanical integrity of the recycled materials under the conditions investigated. Mechanical tests (tensile, tear, hardness, compression set) confirmed that recycled TPS maintains mechanical performance comparable to virgin formulations, while accelerated weathering resulted in minimal color variation and excellent surface appearance retention. Overall, TPS with high recycled content exhibit stable thermal, chemical, and mechanical behavior, confirming their suitability as sustainable alternatives for automotive components.

Polymers doi: 10.3390/polym18131645

Authors: Alba Torres Cenit Soto Javier Carmona Raúl Muñoz Laura Palacio Pedro Prádanos Alberto Tena Antonio Hernández

Mixed-matrix membranes (MMMs) incorporating porous organic fillers into high-performance polyimides were developed to investigate the influence of free volume and molecular architecture on gas transport. Four structurally rigid, intrinsically porous fillers (TFAP-Trp, Is-Trp, TFAP-TPB, and Is-TPB) were incorporated into a range of polymer matrices (P84®, Matrimid®, Pi-DAPOH, Pi-DAROH, Pi-HABAc, Pi-DAM, and PIM-1), enabling the development of a matrix-independent methodology for estimating intrinsic filler permeabilities for five gases (He, O2, N2, CH4, and CO2). This comprehensive multi-matrix, multi-gas study reveals a strong correlation between filler fractional free volume (FFV), BET surface area, and gas permeability, with isatin-based fillers exhibiting particularly high CO2 permeability. Filler incorporation generally resulted in substantial permeability enhancements (100–350%) while maintaining selectivity, often with only minor losses or even favorable improvements in CO2/CH4 and He/CH4 separation performance. Several MMMs, particularly those based on Pi-DAPOH and Pi-DAROH polyimides, approached or exceeded the Robeson upper bound. Analysis of permeability as a function of gas kinetic diameter further elucidated clear structure–property relationships, confirming that filler-induced disruption of polymer chain packing and the creation of additional transport pathways are the primary factors governing separation performance. Overall, these findings demonstrate that rationally designed porous organic fillers provide a robust and broadly applicable strategy for mitigating the permeability–selectivity trade-off in polymer membranes and enhancing gas separation efficiency.

Polymers doi: 10.3390/polym18131644

Authors: Furkan Yapıcı

Chitosan and chitin-derived biomaterials, including native chitosan and chemically modified derivatives, have been widely investigated across orthopedic tissue engineering, implant functionalization, infection control, local delivery, and interface repair, but the evidence is dispersed across heterogeneous formats and indications. This single-author structured narrative review synthesizes 258 unique publications and interprets chitosan through a polymer design, quantitative performance, and clinical translation framework. Literature was identified (January–May 2026) using PubMed/MEDLINE as the primary database, with targeted verification in Web of Science, Scopus, and Google Scholar; no formal risk-of-bias or certainty grading was performed. Chitosan was studied as scaffolds, hydrogels, coatings, nanoparticles, microspheres, fibers, bioadhesives, bone-cement additives, cartilage adjuncts, tendon-to-bone systems, and intervertebral disk biomaterials. The highest human clinical evidence supported BST-CarGel/chitosan–blood implant augmentation of knee marrow stimulation, where randomized, 5-year, and biopsy data favored structural repair over microfracture alone; most other applications—bone regeneration, coatings, osteomyelitis hydrogels, bone cements, tendon/rotator cuff systems, and disk biomaterials—remain preclinical or translational-preclinical. Chitosan should be interpreted as a tunable polymer platform, not a single material; translation requires chemistry-defined formulation, indication-specific mechanical qualification, clinically relevant comparators, and standardized reporting.

Polymers doi: 10.3390/polym18131643

Authors: Samar Ben Atig Bruna F. Gonçalves Moufida Chaari Samia Dhahri Hugo Salazar Fathi Jomni Senentxu Lanceros-Mendez

The remediation of contaminants of emerging concern (CECs) requires innovative, high-efficiency, and sustainable technologies. Here, we investigate active polymeric membranes incorporating TiO2/ZnO heterojunctions for synergistic sono-enhanced photocatalytic water treatment under both UV and visible-light irradiation. TiO2/ZnO composites were synthesized and characterized, confirming the formation of type II heterojunctions with tailored optical properties for sunlight-driven photocatalysis. The catalysts were integrated into poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) matrixes using electrospinning (ES) and thermally induced phase separation (TIPS). ES membranes, specifically the ZnO-rich heterojunction within a PVDF-TrFE matrix (3T-7Z@TrFE ES), achieved the highest performance toward ciprofloxacin (CIP) degradation, reaching 71 and 57% under UV and visible light, respectively. The hybridization of the method by coupling ultrasound induced significant synergistic effects, with relative enhancement factors up to 1.38. Furthermore, the sono-enhanced photocatalytic pathway shifted the degradation mechanism towards the early fragmentation of the harmful piperazine ring, yielding a more sustainable degradation process. In addition, the composite membranes showed selective antibacterial activity against S. aureus, making this a multifunctional platform able not only to degrade CECs but also to mitigate membrane fouling. Overall, this work demonstrates the potential of tailored heterojunctions and composite membranes as sustainable platforms for the remediation of recalcitrant CECs in water, highlighting the synergy between photoactivity, piezoelectricity, and mechanistic control.

Polymers doi: 10.3390/polym18131642

Authors: Mohamed Anwar Ismail Ibrahim Dubdub Suleiman Mousa Abdulrahman Almithn

This study investigated the combustion behaviour of Hassawi rice straw (HRS) at industrially relevant high heating rates through a combination of detailed physicochemical characterisation and non-isothermal thermogravimetric analysis. The biomass was characterised for proximate and ultimate composition, lignocellulosic fibre fractions (Van Soest method), and surface functional groups (FTIR). Thermogravimetric combustion experiments were conducted at heating rates of 20, 40, 60, and 80 K min−1 under oxidative conditions. The results demonstrate that HRS is a promising renewable solid biofuel, with high volatile matter content (72.48 wt%), moderate ash (10.27 wt%), and a higher heating value of 16.04 MJ kg−1. Ultimate analysis revealed low nitrogen (0.67 wt%) and sulphur (0.31 wt%) levels, indicating low potential for NOx and SOx emissions. Thermal decomposition proceeded through three distinct stages, with the main devolatilisation phase occurring between 515 and 680 K due to the breakdown of hemicellulose and cellulose. Kinetic evaluation using six model-free isoconversional methods (FR, FWO, KAS, STK, K, and VY) together with the Coats–Redfern model-fitting approach yielded an average apparent activation energy of 139 kJ mol−1, with the three-dimensional diffusion (D3) model providing the best fit mechanism to the experimental data. Thermodynamic analysis showed positive ΔH and ΔG values with predominantly negative ΔS, confirming the endothermic and non-spontaneous character of the process. These findings offer valuable kinetic and thermodynamic parameters for the design of efficient combustion systems utilising Hassawi rice straw as a sustainable biofuel in arid regions.

Polymers doi: 10.3390/polym18131641

Authors: Lorenzo Novembre Luca Sconosciuto Vito Emanuele Carofiglio Domenico Centrone Alessandro Sannino Antonio Greco

The development of fully biodegradable poly(3-hydroxybutyrate) (PHB)-based materials with improved mechanical performance remains a major challenge due to the limited ductility and processability of this highly crystalline polymer. Blending and plasticisation are viable strategies to enhance PHB toughness; however, the interactions governing polymer–plasticiser compatibility and their impact on structure–property relationships remain not fully understood. In this work, the compatibility and plasticisation mechanisms of two citrate-based plasticisers, tributyl citrate (TBC) and acetyl tributyl citrate (ATBC), were systematically investigated in biodegradable blends based on PHB, polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT). Polymer–plasticiser affinity was evaluated through Hansen Solubility Parameters and interaction radius, which indicated good compatibility of PHB with both plasticisers and a stronger affinity for ATBC. Differential scanning calorimetry showed that citrate plasticisers reduced the glass transition temperature, modified crystallisation kinetics, and altered the crystalline morphology of the blends. Dynamic mechanical analysis confirmed the reduction in the glass transition temperature of PHB–PLA systems, which is in agreement with the DSC results. Migration experiments showed equilibrium after approximately 72 h, with PHB–PLA blends exhibiting better plasticiser retention than PHB–PBAT systems. TBC consistently showed higher migration than ATBC, in line with its lower molecular weight and higher volatility. Mechanical testing demonstrated that plasticisation efficiency strongly depended on blend composition: TBC was more effective in enhancing ductility in PHB–PLA blends, whereas ATBC performed better in PHB–PBAT systems. It was also highlighted that the plasticisers had a remarkable ability to substantially increase the ductility of the blends compared with their unplasticised counterparts, as reflected by the pronounced decrease in stiffness and the marked increase in elongation at break. SEM analysis of tensile fracture surfaces evidenced a brittle failure mode for PHB–PLA blends, whereas PHB–PBAT systems exhibited a ductile fracture mode with fibrillar features and clear signs of phase separation. Finally, thermogravimetric analysis showed no appreciable thermal degradation within the processing temperature window used for mixing and hot pressing, confirming the thermal stability of the materials under the selected conditions. These findings establish clear correlations between thermodynamic compatibility, migration behaviour, thermal properties, fracture mechanisms, and mechanical performance, providing useful guidelines for the design of citrate-plasticised PHB-based biodegradable materials.

Polymers doi: 10.3390/polym18131640

Authors: Azizollah Khormali Soroush Ahmadi

Polymer flooding is one of the most widely implemented chemical-enhanced oil recovery (EOR) techniques for improving sweep efficiency and mobilizing residual oil in mature reservoirs. However, the performance of partially hydrolyzed polyacrylamide (HPAM) flooding is strongly influenced by reservoir temperature, formation water salinity, and polymer concentration, particularly in carbonate formations where harsh reservoir conditions may significantly reduce polymer effectiveness. In this study, laboratory core flooding experiments combined with Response Surface Methodology (RSM) and Analysis of Variance (ANOVA) were employed to systematically investigate and optimize the effects of temperature, HPAM concentration, and salinity on the incremental recovery factor (RF) of matrix-type carbonate core samples. A total of 45 flooding experiments were conducted under temperatures ranging from 20 to 80 °C, polymer concentrations between 500 and 2500 ppm, and salinities from 1000 to 100,000 ppm. A highly significant quadratic model was developed, exhibiting excellent predictive capability (R2 = 0.9991, p < 0.0001) and accurately describing the individual and interactive effects of the investigated variables. Among the examined parameters, HPAM concentration was identified as the dominant factor controlling flooding performance, followed by salinity and temperature. The incremental recovery factor varied from approximately 6 to 19%, and optimization analysis predicted a maximum RF of 18.82% at 20 °C, 2500 ppm HPAM concentration, and 10,000 ppm salinity. Furthermore, optimization under high-temperature and high-salinity conditions revealed that a minimum HPAM concentration of about 2150 ppm is required to maintain RF values above 10%. The proposed experimental–statistical framework provides a reliable tool for predicting and optimizing HPAM flooding performance and offers practical guidance for polymer flooding design in carbonate reservoirs.

Polymers doi: 10.3390/polym18131638

Authors: Ernesto Battaglia Eduart Gutiérrez-Pineda César Barbero Gustavo Abraham Sergio Moya Silvestre Abel

Here, we report a facile, reproducible, fully aqueous route to fabricate citric acid–crosslinked poly(vinyl alcohol) (PVA) composite hydrogels incorporating polyaniline nanoparticles (PANI-NP) of ca. 200 nm mean diameter and polydispersity index (PDI) below 0.2, synthesized directly in water. Nanocomposites incorporating 2, 3, and 5% w/w PANI-NP were thoroughly characterized in terms of thickness (obtaining materials of approximately 500 µm), morphology, spectroscopic and thermal properties, surface properties, swelling behavior, and nanomechanical behavior assessed by atomic force microscopy (AFM) operating in Peak Force Quantitative Nanomechanical Mapping (PF-QNM) mode. Incorporation of PANI-NP progressively increased the elastic modulus of the composites (from 794 MPa for neat PVA to values exceeding several GPa at 3–5% w/w loading) and modified swelling capacity to values as low as 140% (from 247% for neat PVA), reflecting nanoscale interfacial interactions. Notably, the hydrogel composites exhibited significant photothermal activity under low-power near-infrared (NIR) LED irradiation (850 nm, 90 mW cm−2), achieving temperature increases of up to 13.7 °C even at low PANI-NP loadings, with a stable and reproducible response across multiple heating–cooling cycles. Overall, this work establishes a straightforward, water-based fabrication platform for structurally stable, photothermally active nanocomposites with promising potential in light-responsive smart material applications.