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Volume 18
Issue 15
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Polymers, Volume 18, Issue 15 (August-1 2026) – 135 articles

Cover Story (view full-size image): Following O2 plasma treatment, highly hydrophobic PTFE undergoes atmospheric ageing, progressively transitioning toward a hydrophilic state. SEM reveals an accompanying relaxation of surface micro- and nanostructures, while FTIR spectroscopy tracks functional group evolution. Mass spectrometry confirms these chemical modifications originate from plasma–surface interactions, and fractal modelling explains the structural evolution from a rough fractal interface to a smoother geometry. These findings demonstrate that wettability ageing in air is governed by a synergistic interplay between morphological relaxation and chemical restructuring. View this paper
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24 pages, 5026 KB  
Article
Thermal Depolymerization Challenges of PTFE:Silicone Rubber Mixtures and Composite Materials
by Lukas Eigenschink, Matthias Mastalir, Michael Harasek and Christian Paulik
Polymers 2026, 18(15), 1929; https://doi.org/10.3390/polym18151929 - 6 Aug 2026
Viewed by 506
Abstract
Thermochemical depolymerization of polymer mixtures and composite materials is challenging due to non-additive degradation behavior and the emergence of new reaction pathways during pyrolysis. Both polytetrafluoroethylene (PTFE) and silicone rubber (SR) can depolymerize into monomers or low-molecular-weight oligomers when pyrolyzed individually, making them, [...] Read more.
Thermochemical depolymerization of polymer mixtures and composite materials is challenging due to non-additive degradation behavior and the emergence of new reaction pathways during pyrolysis. Both polytetrafluoroethylene (PTFE) and silicone rubber (SR) can depolymerize into monomers or low-molecular-weight oligomers when pyrolyzed individually, making them, in principle, suitable candidates for depolymerization-based recycling. Because they are frequently combined in technical applications and composites, their behavior during co-pyrolysis warrants investigation. However, the pyrolysis of PTFE:SR mixtures and composites remains poorly understood. In this study, we examine the pyrolysis behavior of PTFE:SR systems with emphasis on mass balance, product composition, and the formation of new species to address potential limitations for depolymerization-based recycling. Experiments were conducted on virgin PTFE and SR, defined polymer mixtures, and commercially relevant composites, including PTFE-lined silicone tubing and PTFE:SR septa. The results reveal a pronounced, non-linear dependence of product distribution on PTFE content. Product identification by GC-MS, NMR, and FTIR indicates cleavage of Si–O and Si–CH3 bonds and the formation of fluorinated siloxanes as well as new per- and polyfluoroalkyl substances (PFAS). At low PTFE contents, liquid products are dominated by cyclic siloxanes (Dx). These findings show that depolymerization strategies developed for pure polymers cannot be directly applied to PTFE:SR composites. While systems with low PTFE content may be more amenable to depolymerization, higher PTFE fractions promote the formation of PFAS and difficult-to-valorize fluorinated silicon species. These products complicate selective monomer recovery and could pose significant challenges for the depolymerization-based recycling of PTFE-rich composites. Full article
(This article belongs to the Special Issue Depolymerization: Challenges and Future Trends)
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32 pages, 6040 KB  
Article
Bilayer Scaffold for Corneal Stromal Engineering: Solvent-Cast Polyvinyl Alcohol/Sodium Alginate and Electrospun Aligned Polycaprolactone Fibers
by Amin Orash Mahmoudsalehi, Kevin Stalin Catzim Rios, Carlos Enrique Guerrero-Beltrán and Wendy Ortega-Lara
Polymers 2026, 18(15), 1928; https://doi.org/10.3390/polym18151928 - 6 Aug 2026
Viewed by 365
Abstract
Due to their limited functional range, single-layer engineered scaffolds often fall short of meeting the complex clinical requirements for corneal stromal engineering (CSE). To overcome these challenges, bilayer constructs that integrate complementary material properties have emerged as promising alternatives. In this study, we [...] Read more.
Due to their limited functional range, single-layer engineered scaffolds often fall short of meeting the complex clinical requirements for corneal stromal engineering (CSE). To overcome these challenges, bilayer constructs that integrate complementary material properties have emerged as promising alternatives. In this study, we developed a bilayer membrane by electrospinning polycaprolactone (PCL) fibers onto a solvent-cast polyvinyl alcohol/sodium alginate (PVS) membrane. The dense PVS layer provided a smooth, crack-free surface with favorable physicochemical and thermal stability. In contrast, the PCL nanofibrous layer (232 ± 44 nm) exhibited a continuous, bead-free, and highly aligned morphology. Comprehensive characterization confirmed the structural integrity of the bilayer scaffold, which showed two distinct thermal transitions (~65 °C for PCL and ~225 °C for PVS), confirming good stability and minimal interfacial disruption. Functionally, the PCL–PVS bilayer scaffold demonstrated an intermediate contact angle (57.44°), high water uptake capacity (424.44%), and a high gel fraction (96.12%), along with controlled biodegradation (39.65%), highlighting its suitability for physiological environments. Mechanical testing revealed a Young’s modulus of 2.60 ± 0.20 megapascals (MPa), an ultimate tensile strength (UTS) of 5.74 ± 0.02 MPa, and an elongation at break of 3.32 ± 0.10%, values well aligned with the mechanical demands of corneal tissue. Additionally, the construct achieved 85.01% light transmittance, essential for visual clarity, and supported measurable cell viability, although additional optimization is required to further enhance cytocompatibility. These findings demonstrate that the bilayer combines structural stability, favorable physicochemical performance, transparency, and biological compatibility, positioning it as a promising platform for further optimization toward CSE. Full article
(This article belongs to the Topic Advanced Biomaterials: Processing and Applications, 2nd Edition)
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13 pages, 1405 KB  
Article
Production, Characterization and Antioxidant Activity of Electrospun Nanofibers Using Nettle (Urtica dioica L.) Seed Mucilage-Polyvinyl Alcohol
by Merve Dağcı Tekin
Polymers 2026, 18(15), 1927; https://doi.org/10.3390/polym18151927 - 6 Aug 2026
Viewed by 318
Abstract
This study aimed to develop naturally derived composite nanofibers by incorporating nettle seed mucilage (NSM) into a polyvinyl alcohol (PVA) matrix using the electrospinning method, and to evaluate their potential as functional bio-based materials. The produced nanofibers were characterized in terms of their [...] Read more.
This study aimed to develop naturally derived composite nanofibers by incorporating nettle seed mucilage (NSM) into a polyvinyl alcohol (PVA) matrix using the electrospinning method, and to evaluate their potential as functional bio-based materials. The produced nanofibers were characterized in terms of their morphological, structural and functional properties. The optimized NSM/PVA nanofibers exhibited a smooth, continuous, bead-free and porous morphology with an average fiber diameter of 159.26 nm, indicating the successful production of uniform nanofiber structures. Characterization analyses further confirmed that NSM was effectively integrated into the PVA matrix whilst preserving the composite’s desired structural properties. Furthermore, the incorporation of NSM imparted antioxidant activity to the nanofibers, demonstrating its contribution to the material’s functional performance. Overall, the developed NSM/PVA nanofibers, which combine favorable morphological, structural and functional properties, highlight the potential of stinging nettle seed mucilage as a sustainable natural polymer for the development of bio-based nanofiber composites with potential applications in biomedical coatings, controlled drug delivery, filtration and advanced surface engineering. Full article
(This article belongs to the Special Issue Advances in Electrospun Polymeric Nanofibers)
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22 pages, 7406 KB  
Article
Vacuum-Compatible Electrode-Free Poling of PVDF Films Using Glow-Discharge Plasma
by Bogdan A. Basov, Evgeniya L. Buryanskaya, Kamila T. Makarova, Artur R. Zinnatullin, Konstantin M. Moiseev, Alexey S. Osipkov, Alexander A. Maltsev, Bogdan A. Parshin, Dmitriy S. Ryzhenko and Mstislav O. Makeev
Polymers 2026, 18(15), 1926; https://doi.org/10.3390/polym18151926 - 5 Aug 2026
Viewed by 449
Abstract
Glow-discharge plasma (GDP) poling is revisited as an electrode-free method for activating piezoelectricity in poly(vinylidene fluoride) (PVDF) films. Although this method was proposed several decades ago, its effect on the properties of PVDF films has remained poorly understood. In this work, we demonstrate [...] Read more.
Glow-discharge plasma (GDP) poling is revisited as an electrode-free method for activating piezoelectricity in poly(vinylidene fluoride) (PVDF) films. Although this method was proposed several decades ago, its effect on the properties of PVDF films has remained poorly understood. In this work, we demonstrate that GDP enables efficient poling of oriented PVDF films without pre-deposited electrodes and investigate the relationship between plasma treatment time, structural evolution, and piezoelectric response. Commercially available 25 μm-thick oriented PVDF films (PolyK) were treated in a DC glow discharge for 15 s to 15 min and characterized using FTIR, DSC, piezoresponse force microscopy, UV–Vis–NIR spectrophotometry, quasi-static d33 measurements and water contact-angle measurements. GDP poling produced a side-averaged piezoelectric coefficient d33 of up to ~25 pC/N within 1–5 min, with local maxima at approximately 1, 2.5, and 5 min. This behavior was accompanied by pronounced changes in the domain structure, including an increase in the ferroelectric domain size from 86 to 552 nm, while the crystallinity and electroactive phase fraction changed only moderately. Plasma treatment also increased the wettability of the plasma-facing surface, reducing the water contact angle from about 85° to 42° within 3 min. At longer treatment times (>5 min), however, the piezoelectric response decreased and the optical transparency deteriorated because of increased haze and turbidity, most likely associated with plasma-induced chemical modification of the surface layers. These results indicate that GDP poling has an effective processing window of 1–5 min. The proposed approach provides a vacuum-compatible and electrode-free route for preparing PVDF films with increased surface wettability for flexible piezoelectric sensors, wearable electronics, and integrated polymer-based devices, because it is compatible with electrode deposition on an already activated polymer surface within a single vacuum cycle. Full article
(This article belongs to the Special Issue Advances in Polymer Materials for Sensors and Flexible Electronics)
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35 pages, 13960 KB  
Review
Recent Advances in Carboxymethyl Cellulose-Based Solid Polymer Electrolytes Incorporating Lithium Salts and Functional Additives: A Systematic Review
by Asep Muhamad Samsudin, Ridho Prasetyo, Nur Rokhati, Sun Theo Constan Lotebulo Ndruru, Muhammad Aziz and Viktor Hacker
Polymers 2026, 18(15), 1925; https://doi.org/10.3390/polym18151925 - 5 Aug 2026
Viewed by 488
Abstract
Carboxymethyl cellulose (CMC)-based solid polymer electrolytes (SPEs) have attracted significant attention as sustainable alternatives to conventional liquid electrolytes due to their biodegradability, non-toxicity, and excellent film-forming capability. However, pristine CMC suffers from inherent limitations, including low ionic conductivity, poor mechanical strength, and limited [...] Read more.
Carboxymethyl cellulose (CMC)-based solid polymer electrolytes (SPEs) have attracted significant attention as sustainable alternatives to conventional liquid electrolytes due to their biodegradability, non-toxicity, and excellent film-forming capability. However, pristine CMC suffers from inherent limitations, including low ionic conductivity, poor mechanical strength, and limited electrochemical stability. This systematic literature review comprehensively evaluates recent advances in CMC-based SPEs, focusing on the roles of lithium salts (e.g., LiCH3COO, LiClO4, LiI, LiBF4, and LiNO3) and functional additives, including plasticizers, ionic liquids, nanofillers, and cross-linking agents, in tailoring the physicochemical and electrochemical properties. The findings reveal that ionic conductivity can be significantly enhanced from ~10−7 to 10−2 S cm−1 through synergistic modifications that reduce crystallinity and promote segmental mobility. Electrochemical stability is improved by up to ~3.85 V with the incorporation of ionic liquids, while ion transference numbers approaching unity (t+ ≈ 0.96) indicate highly efficient Li+-dominated transport. Mechanical properties exhibit a trade-off between flexibility (elongation up to ~699%) and tensile strength (up to ~12.84 MPa), depending on the balance between plasticization and cross-linking. The degradation temperature is also strongly influenced by system composition, reaching ~508 °C in ionic liquid-modified systems. Overall, the performance of CMC-based SPEs is governed by the interplay between salt chemistry, polymer structure, and additive functionality. This review highlights key structure–property relationships and identifies critical research gaps, including salt-concentration optimization, long-term stability, and scalability, providing strategic insights for the rational design of high-performance, sustainable polymer electrolytes for next-generation energy storage applications. Full article
(This article belongs to the Topic Advanced Battery Materials and Technologies)
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26 pages, 14778 KB  
Article
Synergistic Optimisation of Surface Properties and Surface Quality of FDM ABS Specimens Based on RSM and CWOA
by Jing Zhao, Rui Zhu, Hairui Ma, Xinyan Li, Li Yang, Pei Li, Shuangjun Wang and Tianlu Wei
Polymers 2026, 18(15), 1924; https://doi.org/10.3390/polym18151924 - 5 Aug 2026
Viewed by 301
Abstract
The surface roughness (Ra) and coefficient of friction (COF) of acrylonitrile butadiene styrene (ABS) parts fabricated through fused deposition modelling (FDM) are key determinants of their functional service performance. However, these two objectives often present a trade-off relationship in single-objective optimisation. To achieve [...] Read more.
The surface roughness (Ra) and coefficient of friction (COF) of acrylonitrile butadiene styrene (ABS) parts fabricated through fused deposition modelling (FDM) are key determinants of their functional service performance. However, these two objectives often present a trade-off relationship in single-objective optimisation. To achieve synergistic optimisation of surface quality and surface performance of FDM ABS parts, this paper proposes a multi-objective optimisation framework integrating response surface methodology (RSM) with a chaotic whale optimisation algorithm (CWOA). A Box–Behnken design (BBD) was employed to establish quadratic regression models for Ra and COF as functions of layer thickness (0.16–0.24 mm), extrusion ratio (0.9–1.0), infill density (20–100%) and extrusion temperature (240–270 °C). Based on analysis of variance (ANOVA) and response surface analysis, a non-linear mathematical model with dual responses was constructed. Pareto-dominated CWOA was introduced for multi-objective optimisation, and the optimal process parameter combination was selected using the TOPSIS method. The results showed that the optimal parameters were: layer thickness 0.16 mm, extrusion ratio 0.9, infill density 66%, and extrusion temperature 270 °C. Under these conditions, the experimentally measured Ra was 7.7921 μm (2.04% error from the predicted value) and COF was 0.1504 (2.80% error from the predicted value). Compared with the benchmark reference (the average value of the BBD central experimental runs), a synchronous decrease in Ra and COF was achieved (Ra reduced by 27.4% and COF reduced by 14.9%). Metallographic morphology analysis revealed that the optimal specimen surface exhibited wide filament ridges, narrow and well-defined inter-filament valleys, and no obvious forming defects, achieving synergistic low roughness and low friction. The proposed RSM-CWOA framework provides an effective method for multi-objective optimisation of FDM processes and can be extended to other polymer additive manufacturing systems. Full article
(This article belongs to the Section Polymer Processing and Engineering)
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44 pages, 55656 KB  
Article
Mechanical Durability of Polymer-Encapsulated Electronic Yarns for Electronic Textile Applications
by Tharushi Peiris, Lukas Werft, Sigrid Rotzler, Arash M. Shahidi, Kalana Marasinghe, Carlos Oliveira, Tilak Dias and Theo Hughes-Riley
Polymers 2026, 18(15), 1923; https://doi.org/10.3390/polym18151923 - 5 Aug 2026
Viewed by 428
Abstract
This study presents a standalone yarn-level assessment of the mechanical and functional durability of polymer-encapsulated electronic yarns (E-yarns) for wearable electronic textile applications. The investigated E-yarns consisted of miniaturised electronic components soldered onto fine conductive wires, protected by polymer encapsulation, and enclosed within [...] Read more.
This study presents a standalone yarn-level assessment of the mechanical and functional durability of polymer-encapsulated electronic yarns (E-yarns) for wearable electronic textile applications. The investigated E-yarns consisted of miniaturised electronic components soldered onto fine conductive wires, protected by polymer encapsulation, and enclosed within braided textile yarn structures. This heterogeneous architecture enables textile-compatible functionality but creates local regions that may be susceptible to damage under various deformation modes. E-yarns incorporating light-emitting diode, photodiode, and resistor components were evaluated under cyclic bending fatigue, torsional fatigue, quasi-static tensile loading, and wash durability conditions. Electrical measurements were used to monitor functional degradation and failure, while X-ray imaging, scanning electron microscopy and finite element analysis were used to examine structural damage, failure localisation, fracture surface morphology, and local stress and strain distribution. The results show that E-yarn durability depended on the imposed loading condition, with distinct mechanical and functional responses observed across the different test modes. The polymer-encapsulated region emerged as a mechanically important feature of the E-yarn architecture, particularly at transitions between encapsulated and non-encapsulated regions. By addressing multiple deformation and loading conditions at the standalone yarn level, this work provides a systematic reliability assessment of polymer-encapsulated E-yarns, enabling intrinsic failure mechanisms to be distinguished from textile integration effects and supporting the development of more reliable yarn-based electronic textiles. Full article
(This article belongs to the Special Issue Functional Polymers for Wearable Technology)
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32 pages, 6439 KB  
Article
Effect of Natural Zeolite Modification Route on the Catalytic Pyrolysis of Post-Consumer Polystyrene Toward Styrene-Rich Liquid Products
by Joaquin Hernandez-Fernandez, Rafael Gonzalez-Cuello and Rodrigo Ortega-Toro
Polymers 2026, 18(15), 1922; https://doi.org/10.3390/polym18151922 - 5 Aug 2026
Viewed by 352
Abstract
The catalytic pyrolysis of post-consumer polystyrene (PS) offers a potential route to obtain styrene-rich liquid fractions from plastic waste. In this study, natural zeolites were modified by thermal activation (AT-ZN), acid treatment (AA-ZN), and protonic ion exchange (H-ZN), and their performance was evaluated [...] Read more.
The catalytic pyrolysis of post-consumer polystyrene (PS) offers a potential route to obtain styrene-rich liquid fractions from plastic waste. In this study, natural zeolites were modified by thermal activation (AT-ZN), acid treatment (AA-ZN), and protonic ion exchange (H-ZN), and their performance was evaluated under different pyrolysis temperatures (400–500 °C), heating rates (10–20 °C min−1), and catalyst loadings (5–10 wt.%). Thermogravimetric analysis indicated that zeolite incorporation shifted the apparent PS degradation profile toward lower temperatures, suggesting that the modified solids altered the polymer’s thermal conversion behavior. Product-yield analysis showed that H-ZN provided the most favorable phase distribution, producing high liquid fractions while limiting solid-residue formation. AT-ZN exhibited an intermediate, comparatively stable response. In contrast, AA-ZN promoted greater solid formation and lower liquid recovery, suggesting that more severe catalytic conditions may favor secondary reactions and the accumulation of carbonaceous residues. Targeted GC–MS analysis revealed that styrene was the dominant aromatic compound among the quantified products, with H-ZN consistently showing the highest styrene proportion in the analyzed liquid fraction. Correlation analysis and ANOVA further indicated that the influence of temperature, catalyst loading, and their interactions depended strongly on the zeolite modification route. Overall, the results demonstrate that the route of modification of the natural zeolite strongly affected its composition, textural properties, acidity distribution, thermal behavior, and catalytic performance during PS pyrolysis. XRF, N2 adsorption–desorption, NH3-TPD, TGA/DTG, and FTIR characterization showed that AA-ZN exhibited the highest Si/Al ratio and BET surface area, whereas H-ZN presented the highest total acidity and the largest contribution of medium- and strong-acid sites. The combined characterization and pyrolysis results indicate that the preservation of styrene-rich liquid products was governed by the balance between acid-site distribution and pore accessibility, rather than by surface area or total acidity considered in isolation. Full article
(This article belongs to the Special Issue Depolymerization: Challenges and Future Trends)
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23 pages, 7761 KB  
Article
Experimental Exploration of Properties and Characterization of Nerium oleander L. Plant Stem Fibers and Their Polymer Composites
by M. Ramesh, M. Tamil Selvan, A. Felix Sahayaraj, P. Ramya, C. Deepa and M. Sathishkumar
Polymers 2026, 18(15), 1921; https://doi.org/10.3390/polym18151921 - 5 Aug 2026
Viewed by 369
Abstract
This study aimed to investigate the physicochemical properties and composites of a novel cellulosic fiber extracted from Nerium oleander L. plant stem. Nerium oleander fibers (NOFs) were separated from mature oleander plants using a microbial degradation technique, and their composites (NOFCs) were fabricated [...] Read more.
This study aimed to investigate the physicochemical properties and composites of a novel cellulosic fiber extracted from Nerium oleander L. plant stem. Nerium oleander fibers (NOFs) were separated from mature oleander plants using a microbial degradation technique, and their composites (NOFCs) were fabricated using a compression molding technique. The chemical composition, physical and thermal behavior of NOFs, and mechanical and water absorption properties of NOFs and NOFCs were investigated. The findings show that NOFs have a cellulose content of 57%, hemicellulose content of 13%, lignin content of 16%, density of 1.46 g/cc, and crystallinity index (CI) of 57.14%. The results further revealed that NOFs had a tensile strength of 438 MPa and a strain rate of 1.8%, whereas NOFCs had a maximum tensile strength of 58.42 MPa. NOFs can withstand temperatures up to 357 °C, according to a thermogravimetric study, and the functional groups were analyzed using Fourier-transform infrared (FTIR) spectroscopy. Scanning electron microscopy (SEM) studies showed that the surface morphology and fractured surfaces of the NOFs and their composites were smooth and circular in cross-section. Full article
(This article belongs to the Special Issue Fiber Reinforced Polymer Composites: Preparation, Applications and Prospects)
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29 pages, 7669 KB  
Article
Glycine-Functionalized Polycaprolactone Electrospun Nanofibers as Bioactive Scaffolds for Skin Repair
by Leonardo Prieto-Abello, Liliana Lizarazo-Fonseca, Gustavo Salguero and Ingrid Silva-Cote
Polymers 2026, 18(15), 1920; https://doi.org/10.3390/polym18151920 - 5 Aug 2026
Viewed by 630
Abstract
Chronic cutaneous ulcers pose a major clinical challenge due to persistent inflammation, impaired angiogenesis, and limited regenerative capacity, underscoring the need to develop bioactive scaffolds that mimic the extracellular matrix (ECM) and promote skin repair. In this study, electrospun Poly(ε-caprolactone) (PCL) scaffolds functionalized [...] Read more.
Chronic cutaneous ulcers pose a major clinical challenge due to persistent inflammation, impaired angiogenesis, and limited regenerative capacity, underscoring the need to develop bioactive scaffolds that mimic the extracellular matrix (ECM) and promote skin repair. In this study, electrospun Poly(ε-caprolactone) (PCL) scaffolds functionalized with 10% (PCLGLI10) and 20% (PCLGLI20) glycine were fabricated, physicochemically and mechanically characterized, and evaluated in combination with human Wharton’s jelly mesenchymal stromal cells (hWJ-MSCs). Glycine incorporation reduced fiber diameter to the nanoscale range (140–155 nm) and increased scaffold porosity (~71–72%) while preserving mechanical properties compatible with skin. FTIR and X-ray diffraction analyses confirmed glycine incorporation and a polymorphic transition from α- to γ-glycine during electrospinning. Cell viability remained above 95% in all scaffolds; however, PCLGLI10 significantly enhanced cell proliferation, metabolic activity, and the secretion of VEGF and HGF, mediators associated with angiogenesis and tissue repair. Furthermore, in a guinea pig full-thickness wound model, the PCLGLI10+hWJ-MSCs construct promoted a modulated inflammatory response and more organized collagen deposition. These findings support the potential of glycine-functionalized electrospun scaffolds as a promising strategy for chronic cutaneous ulcer regeneration. Full article
(This article belongs to the Special Issue Biobased Polymer Composites for Biomedical Applications)
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15 pages, 2592 KB  
Article
One-Step Preparation of Silk Fibroin and Sericin from Silkworm Cocoons Using High-Temperature High-Pressure Treatment
by Yeon Jin Kim, Bo Kyung Park, Ick Soo Kim and In Chul Um
Polymers 2026, 18(15), 1919; https://doi.org/10.3390/polym18151919 - 5 Aug 2026
Viewed by 524
Abstract
Conventional silk degumming processes are primarily designed to recover either silk fibroin (SF) or sericin, resulting in inefficient utilization of silk resources and substantial sericin waste. In this study, a one-step high-temperature high-pressure (HTHP) process was developed for the simultaneous preparation of SF [...] Read more.
Conventional silk degumming processes are primarily designed to recover either silk fibroin (SF) or sericin, resulting in inefficient utilization of silk resources and substantial sericin waste. In this study, a one-step high-temperature high-pressure (HTHP) process was developed for the simultaneous preparation of SF and sericin from silkworm cocoons. To determine the optimum processing conditions, HTHP treatment was performed at 120 °C for 10, 20, and 30 min. The effects of treatment time on the degumming efficiency and the physicochemical properties of SF and sericin were systematically investigated through the characterization of SF as degummed fibers, regenerated solutions, and electrospun fibers, and sericin as solutions and gels. Complete degumming was achieved after 10 min of HTHP treatment, corresponding to a degumming ratio of 25.4%, with no further increase at longer treatment times. While complete degumming was maintained beyond 10 min, prolonged treatment progressively deteriorated the physicochemical properties of sericin and eventually reduced the molecular integrity of SF, as consistently demonstrated across the different material forms. Compared with the conventional soap/soda method, the HTHP process better preserved the molecular integrity of SF while simultaneously recovering an aqueous sericin fraction without chemical degumming. Based on the degumming efficiency and the physicochemical properties of both silk proteins, 10 min was identified as the optimum HTHP treatment time for the simultaneous preparation of SF and sericin. This one-step HTHP process provides a simple and efficient process for improving silk resource utilization and facilitating the industrial production of SF and sericin-based biomaterials. Full article
(This article belongs to the Special Issue Biomass to Biopolymers: Sustainable Materials Engineering)
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18 pages, 2479 KB  
Article
Adhesion and Hydrothermal Performance of Epoxy–Dicyandiamide Adhesive Film for PMMA-PETR
by Guoliang Yu, Lei Wang, Yue Li, Hu Lyu, Dongzhou Sun, Wei Dong, Shudi Liu, Yanting Du, Kexin Ning, Dawei Zhang, Zhiqiang Ning and Xianzhi Kong
Polymers 2026, 18(15), 1918; https://doi.org/10.3390/polym18151918 - 5 Aug 2026
Viewed by 570
Abstract
Epoxy/dicyandiamide adhesive film is required for the bonding of polymethyl methacrylate (PMMA) aircraft cockpit edges. An imidazole/alkanolamine composite accelerator was developed to satisfy the requirement of maintaining a bonding temperature below 90 °C for this structure, successfully reducing the curing temperature of the [...] Read more.
Epoxy/dicyandiamide adhesive film is required for the bonding of polymethyl methacrylate (PMMA) aircraft cockpit edges. An imidazole/alkanolamine composite accelerator was developed to satisfy the requirement of maintaining a bonding temperature below 90 °C for this structure, successfully reducing the curing temperature of the adhesive film from 180 °C to 85 °C. The curing process of the low-temperature curing adhesive film and its hydrothermal aging resistance after curing were investigated using mechanical testing, Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The results indicate that the curing process of 85 °C for 6 h enables the adhesive film to fulfill the adhesion strength requirements for aircraft cockpit edge applications. The cured adhesive film is found to exhibit limited intrinsic water resistance due to its low crosslinking density. Therefore, external edge sealing is required in practical engineering applications to isolate moisture. This work provides an application-specific one-component epoxy/dicyandiamide adhesive film for the low-temperature flexible bonding of aviation PMMA cockpit edges to PETR, and clarifies its adhesion performance and hydrothermal aging behavior under the target service scenario. Full article
(This article belongs to the Special Issue Advances in High-Performance Polymers: Innovative Adhesives and Composites)
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19 pages, 20456 KB  
Article
Upgrading of Automotive Polymer Fractions Obtained by a Flotation Separation Process: Properties and Structure
by Wiktoria Kanciak, Dorota Czarnecka-Komorowska and Mikołaj Popławski
Polymers 2026, 18(15), 1917; https://doi.org/10.3390/polym18151917 - 5 Aug 2026
Viewed by 338
Abstract
This study investigated the upgrading process of polymer fractions obtained from automotive waste by a three-stage flotation–sedimentation separation process. The separated automotive recycled blend (ARB) fraction was modified with a compatibiliser at contents of 5, 10 and 15 wt%, and the resulting blends [...] Read more.
This study investigated the upgrading process of polymer fractions obtained from automotive waste by a three-stage flotation–sedimentation separation process. The separated automotive recycled blend (ARB) fraction was modified with a compatibiliser at contents of 5, 10 and 15 wt%, and the resulting blends were processed by extrusion and injection moulding. Multipoint FTIR analysis confirmed the multicomponent character of the ARB fraction and indicated the presence of, among others, polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), high-density polyethylene (HDPE) and polystyrene (PS). The influence of compatibiliser addition on density, Shore D hardness, tensile properties, thermal behaviour and fracture-surface morphology was evaluated using gas pycnometry, static tensile testing, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that increasing compatibiliser content gradually reduced the density of the blends, while hardness remained at a level comparable to that of the reference material. Tensile testing indicated that the addition of the compatibiliser reduced Young’s modulus, whereas ultimate tensile strength and tensile stress at break were maintained close to the unmodified blend. Among the modified blends, the most favourable balance of the evaluated properties was observed for the ARB/10C sample containing 10 wt% compatibiliser. This blend exhibited the highest tensile stress at break among the investigated blends and a comparatively compact fracture-surface morphology. DSC analysis showed similar principal thermal transition ranges for all blends. The results indicate that 10 wt% compatibiliser is an optimal addition for upgrading recycled automotive polymer fractions. Full article
(This article belongs to the Special Issue Recycling of Engineering Polymers: Process and Physico-Chemical Changes, 2nd Edition)
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16 pages, 9633 KB  
Article
Oxygen-Content-Dependent Interfacial and Barrier Effects of Graphene Fillers in PVA Adhesives Toward Durable Polarizer Applications
by Chang Sun, Wentao Huang, Ziyuan Zheng, Rui Huang, Qinghua Zhao and Guohua Chen
Polymers 2026, 18(15), 1916; https://doi.org/10.3390/polym18151916 - 5 Aug 2026
Viewed by 431
Abstract
Waterborne poly(vinyl alcohol) (PVA) adhesives are widely used in iodine-based polarizers, owing to their excellent transparency and interfacial adhesion. However, the intrinsic hydrophilicity of PVA compromises the long-term durability of polarizers under humid conditions. Herein, graphene derivatives with tunable oxygen contents and graphitization [...] Read more.
Waterborne poly(vinyl alcohol) (PVA) adhesives are widely used in iodine-based polarizers, owing to their excellent transparency and interfacial adhesion. However, the intrinsic hydrophilicity of PVA compromises the long-term durability of polarizers under humid conditions. Herein, graphene derivatives with tunable oxygen contents and graphitization degrees, including graphene oxide (GO), partially reduced graphene oxide (rGO), and graphene nanosheets (GNs), were incorporated into a PVA/PEI adhesive system to investigate the oxygen-content-dependent interfacial interactions and moisture-barrier mechanisms. Structural analyses reveal that oxygen-rich GO enhances interfacial hydrogen bonding and polymer–graphene interactions, whereas highly graphitized GN primarily functions through its intrinsic lamellar barrier effect by increasing diffusion tortuosity and reducing water affinity. The rGO exhibits a compromise between interfacial interactions and barrier effects due to its moderate oxygen content and preserved graphene structure. Among them, the GN-modified adhesive demonstrates the most favorable overall performances, achieving a 14.71% reduction in the water vapor transmission rate (WVTR) of the assembled polarizer, enhanced moisture resistance, and improved antistatic capability while maintaining acceptable optical transparency. Furthermore, practical polarizer evaluations confirm that GN effectively suppresses moisture penetration, with only slight bubbling observed after 8 days of water immersion and no delamination or polarization degradation during a 40-day immersion test. These findings provide insights into the relationship between graphene oxygen content, interfacial interactions, and moisture-barrier behavior, offering an effective strategy for designing durable multifunctional waterborne adhesives for advanced optoelectronic polarizer applications. Full article
(This article belongs to the Section Polymer Composites and Nanocomposites)
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21 pages, 11044 KB  
Article
Effect of Long-Term Outdoor Storage on the Multi-Scale Structural and Mechanical Properties of Oriental Beech (Fagus orientalis Lipsky) and European Hornbeam (Carpinus betulus L.) Wood
by Göksu Şirin
Polymers 2026, 18(15), 1915; https://doi.org/10.3390/polym18151915 - 5 Aug 2026
Viewed by 383
Abstract
This study examines the effects of nearly six years of outdoor storage on the chemical, thermal, structural, micromorphological, and mechanical properties of European hornbeam (Carpinus betulus L.) and Oriental beech (Fagus orientalis Lipsky) wood. Differences between fresh (control) and stored samples [...] Read more.
This study examines the effects of nearly six years of outdoor storage on the chemical, thermal, structural, micromorphological, and mechanical properties of European hornbeam (Carpinus betulus L.) and Oriental beech (Fagus orientalis Lipsky) wood. Differences between fresh (control) and stored samples were characterised using attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, thermogravimetric/derivative thermogravimetric analysis (TGA/DTG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and testing of compressive strength parallel to the grain. ATR-FTIR analysis points to alterations in carbohydrate- and lignin-related absorption bands after storage. TGA/DTG profiles suggest that hornbeam largely maintains its thermal degradation behaviour, whereas beech exhibits more pronounced shifts in thermal stability. XRD results indicate a reduction in crystallinity index (CrI) for both species. SEM observations of beech wood revealed filamentous structures within cell lumens, together with localised cell-wall disruption and microcracks, indicating more extensive microstructural modification than in hornbeam. Mechanical testing shows significant reductions in modulus of elasticity (MOE), with decreases of 32.2% in hornbeam and 28.4% in beech. Statistical evaluation confirms the significance and effect sizes of these changes. Overall, the findings demonstrate that long-term outdoor storage induces species-dependent degradation across molecular, microstructural, and macroscopic scales, ultimately compromising wood performance. Full article
(This article belongs to the Special Issue Natural Polymeric Materials: Polysaccharides and Carbohydrate Polymers, 2nd Edition)
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28 pages, 9502 KB  
Article
The Effect of Glass Fiber-Reinforced Mortars on Physical and Mechanical Performance: An Examination of Length and Ratios
by Suna Cetin, Ahmet Filazi and Reyhan Akat
Polymers 2026, 18(15), 1914; https://doi.org/10.3390/polym18151914 - 4 Aug 2026
Viewed by 303
Abstract
This study systematically investigates the combined effects of three different glass fiber lengths (3, 6, and 12 mm) and three different fiber ratios (1%, 2%, and 3%) on the physical, mechanical, and microstructural properties of cement mortars. Glass fibers are known to enhance [...] Read more.
This study systematically investigates the combined effects of three different glass fiber lengths (3, 6, and 12 mm) and three different fiber ratios (1%, 2%, and 3%) on the physical, mechanical, and microstructural properties of cement mortars. Glass fibers are known to enhance mortar performance, yet the simultaneous influence of fiber length and proportion on fresh, hardened, durability, and microstructural characteristics has not been comprehensively addressed in a single experimental framework. The parameters investigated include flow diameter, dry unit weight, water absorption, flexural and compressive strength (at 7 and 28 days), ultrasonic pulse velocity, water sorptivity, as well as SEM/EDS and XRD analyses. Results demonstrated that increasing fiber length and content decreased flow diameter and increased porosity within the mortar compositions. At a 3% fiber inclusion, dry unit weight values decreased, with the lowest value (below 2100 kg/m3) observed for the 12 mm-3% mixture. Flexural strength results highlighted the critical role of the curing process on fiber-matrix interface development. At 7 days, only 1% fiber content improved flexural strength, while higher contents reduced it. At 28 days, however, increasing fiber content generally enhanced flexural strength, particularly for 6 mm fibers, albeit at the expense of compressive strength. The capillarity test revealed that the optimal fiber proportion was 1%, with mixtures achieving compressive strengths exceeding 50 MPa and capillarity coefficients below 0.10 mm/min0.5, while higher fiber contents led to elevated capillarity coefficients. The study concluded that, under the specific conditions tested, the most suitable fiber length is 6 mm, with a recommended fiber content of 1–2%. The 6 mm-1% combination delivered the best overall performance, achieving 60.18 MPa compressive strength, a capillarity coefficient below 0.10 mm/min0.5, and enhanced flexural strength. While increasing fiber content improved flexural strength, it reduced compressive strength and increased the capillarity coefficient. These findings underscore the importance of using appropriate fiber proportions to optimize mortar performance and provide practical guidance for designing fiber-reinforced mortars in structural and construction applications. Full article
(This article belongs to the Section Polymer Fibers)
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20 pages, 7002 KB  
Article
Performance of Cold Recycled Micro-Surfacing with WER Asphalt and Ultrasonic–Mechanical Pre-Regenerated RAP
by Jie Yang, Mengmei Liu, Lihong Zhang, Yu Wang, Xinchun Gao, Jingwen Shi and Demei Yu
Polymers 2026, 18(15), 1913; https://doi.org/10.3390/polym18151913 - 4 Aug 2026
Viewed by 601
Abstract
Recycled micro-surfacing is a sustainable pavement maintenance technique, yet using fine Reclaimed Asphalt Pavement (RAP) is challenging due to aged asphalt and particle agglomeration. This study aimed to develop cold recycled micro-surfacing with waste edible oil (WEO) and Waterborne Epoxy Resin (WER)-modified emulsified [...] Read more.
Recycled micro-surfacing is a sustainable pavement maintenance technique, yet using fine Reclaimed Asphalt Pavement (RAP) is challenging due to aged asphalt and particle agglomeration. This study aimed to develop cold recycled micro-surfacing with waste edible oil (WEO) and Waterborne Epoxy Resin (WER)-modified emulsified asphalt and proposed a novel pre-regeneration method using ultrasonic–mechanical mixing for fine RAP with WEO before preparing mixtures. Molecular dynamics (MD) simulation and Dynamic Shear Rheometer (DSR) tests were conducted to assess rejuvenator diffusion and rheological recovery. In addition, mixtures with 0–25% WER were tested for wear, rutting, low-temperature splitting, and water resistance to optimize the WEO content, mixing time, and WER dosage. The results of MD simulation showed that WEO diffused faster than aged asphalt molecules and mutually interacted. DSR results indicated that 4% WEO (by mass of aged asphalt) gradually restored the complex modulus and phase angle to the levels of matrix asphalt. The recycled mixtures with 4 min ultrasonic–mechanical mixing had a minimum WTAT of 136.86 g/m2, which was a 9.6% decrease compared to the mixture without ultrasonic–mechanical mixing. The 1 h WTAT, PVD, PLD, 6d WTAT, and tensile strength of recycled mixtures with 20% WER were improved by 72.6%, 68.9%, 68.8%, 75.0%, and 88.7% compared with those of the matrix asphalt mixtures. Although WER weakened the low-temperature performance of the mixtures, the tensile strain was smaller than the maximum specification requirement of 2500 με when the WER content was less than 20%. In summary, pre-regeneration with 0.4% WEO (by mass of mixtures) and 4 min ultrasonic–mechanical mixing effectively activated the fine RAP. Considering the balance of properties of fine RAP micro-surfacing mixtures, the optimum dosage of 20% WER was recommended to provide sustainable high-performance cold recycled micro-surfacing. Full article
(This article belongs to the Section Circular and Green Sustainable Polymer Science)
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14 pages, 4737 KB  
Article
Fabrication, Simulation, and Mechanical Characterization of Curcumin-Loaded PVA/PVP Microneedle Arrays Using Custom 3D-Printed Molds
by Bryan Angelo S. J. Basa, Charlize Dawn Z. Batin, Izabelle Nisha Maxine D. Chan, Adrian Ray B. Gabay, John Ray C. Estrellado, Ron Gilbert R. Rallos, Mary Stephanie S. Carranza, Mark Jefferson U. Lim, Jubert C. Marquez and Joseph Rey H. Sta Agueda
Polymers 2026, 18(15), 1912; https://doi.org/10.3390/polym18151912 - 4 Aug 2026
Viewed by 782
Abstract
Microneedle (MN) arrays offer a novel and minimally invasive platform for transdermal drug delivery. This study presents an approach for the design and fabrication of MN array models for biomedical applications using custom 3D-printed micro-molds. Material analysis of the polyvinyl alcohol (PVA) and [...] Read more.
Microneedle (MN) arrays offer a novel and minimally invasive platform for transdermal drug delivery. This study presents an approach for the design and fabrication of MN array models for biomedical applications using custom 3D-printed micro-molds. Material analysis of the polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) matrix in a 3:1 weight ratio was conducted under varying geometric configurations, curcumin (CUR) dosages, and target penetration depths of 300 to 500 μm. Computational simulation using computer-aided design (CAD) and finite element analysis (FEA) on ANSYS (Canonsburg, PN, USA) measured for total deformation, stress distribution, insertion pressure, and factor of safety. Elimination criteria were applied, narrowing down to specific models that were experimentally validated through material formulation, micro-molding, and material characterization. The selected MN models were analyzed by insertion and penetration efficiency testing on porcine skin. The results showed that higher CUR concentrations reduced mechanical strength and Young’s modulus, while mid-range dosages (2–6 mg) combined with optimized geometric spacing produced MNs with maintained structural integrity and effective performance. Conical microneedles demonstrated the most favorable balance of mechanical stability, controlled swelling behavior, and high insertion efficiency. The study recommends this approach as a feasible and reproducible method for localized wound-healing applications. Full article
(This article belongs to the Special Issue Natural Biopolymers for Biomedical Applications)
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26 pages, 7796 KB  
Article
Development and Biological Evaluation of Aronia melanocarpa Extract-Loaded Gelatin–Collagen Nanofibers on B16F10 Cell
by İrem Gün, Rukiye Yiğit, Filiz Altay and Büşra Yusufoğlu
Polymers 2026, 18(15), 1911; https://doi.org/10.3390/polym18151911 - 4 Aug 2026
Viewed by 714
Abstract
Background: Aronia melanocarpa is a sustainable source of phenolic compounds and anthocyanins with antioxidant and biological activities; however, the instability of these compounds limits their application. This study aimed to develop gelatin–collagen electrospun nanofibers loaded with Aronia melanocarpa extract (AME) to improve phytochemical [...] Read more.
Background: Aronia melanocarpa is a sustainable source of phenolic compounds and anthocyanins with antioxidant and biological activities; however, the instability of these compounds limits their application. This study aimed to develop gelatin–collagen electrospun nanofibers loaded with Aronia melanocarpa extract (AME) to improve phytochemical stability. Methods: AME-loaded nanofibers were produced by electrospinning and evaluated for their physicochemical properties, antioxidant activity, antimicrobial effects, antiproliferative potential, and molecular interactions with epidermal growth factor receptor (EGFR). Results: AME incorporation increased the viscosity from 0.66 to 1.54 Pa·s and the fiber diameter from 0.39 to 0.84 μm while reducing the contact angle from 39.71° to 28.83°. The total phenolic content increased from 19.365 to 48.775 mg GAE/g, and the antioxidant capacity increased from 2.852 to 7.880 mg TE/g. At 500 μg/mL, AME reduced the maximum growth rate of S. aureus from 0.227 to 0.121 OD600/h and prolonged the lag phase, indicating a 53% bacteriostatic effect. While Cyanidin-3-O-glucoside (Cy3G) was the dominant anthocyanin, cyanidin showed the highest retention rate after electrospinning, and cyanidin-3-rutinoside demonstrated strong interaction with EGFR (−9.0 kcal/mol). Conclusions: AME-loaded nanofibers are potential sustainable products for health applications. Full article
(This article belongs to the Section Polymer Fibers)
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15 pages, 3092 KB  
Article
Constructing High-Transparency, Self-Healing and Reprocessable Poly(thiourethane) Elastomers Based on Zn2+-Multidentate Pyrimidine Coordination
by Na Wei, Hanxu Zhu, Bing Li and Weijun Yang
Polymers 2026, 18(15), 1910; https://doi.org/10.3390/polym18151910 - 4 Aug 2026
Viewed by 444
Abstract
To develop self-healing polyurethane materials with high transparency and superior mechanical performance, in this work, the poly(thiourethane) elastomers were prepared by incorporating the dynamic thiourethane bonds via thiol–isocyanate click reaction, followed by the addition of 1-(3-aminopropyl)imidazole (IZ), 3-hydroxypyridine (HP), and 2,4-diamino-6-hydroxypyrimidine (HPM) as [...] Read more.
To develop self-healing polyurethane materials with high transparency and superior mechanical performance, in this work, the poly(thiourethane) elastomers were prepared by incorporating the dynamic thiourethane bonds via thiol–isocyanate click reaction, followed by the addition of 1-(3-aminopropyl)imidazole (IZ), 3-hydroxypyridine (HP), and 2,4-diamino-6-hydroxypyrimidine (HPM) as ligands to produce three different polyurethane networks (named PTU-IZ, PTU-HP, and PTU-HPM). Zinc chloride (ZnCl2) was further introduced to construct metal-coordinated crosslinking networks, recorded as PTU-IZ-Zn, PTU-HP-Zn, and PTU-HPM-Zn, respectively. The effects of ligands and Zn2+ coordination on the materials’ optical transmittance, mechanical properties, self-healing capability, and reprocessability were systematically investigated. The results demonstrate that HPM and Zn2+ will facilitate the formation of more effective crosslinking, which significantly enhances the mechanical properties of PTU-HPM from 4.61 MPa up to 9.04 MPa (PTU-HPM-Zn), while maintaining high transparency (89.0% light transmittance at 650 nm). Self-healing tests reveal that the PTU-HPM-Zn scratches can fully repair within 4 h at 70 °C. Reprocessability tests demonstrate that the internal crosslinked network of the material undergoes reversible dissociation, enabling a topological transition from a crosslinked to a linear structure and thereby imparting excellent thermal reprocessability. This study provides novel insights for the design and fabrication of high-performance transparent self-healing polyurethane materials. Full article
(This article belongs to the Section Polymer Networks and Gels)
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12 pages, 6866 KB  
Article
Does Thermoforming Setup Affect Thickness in Thermoplastic Orthodontic Appliances? A Comparison of Single vs. Dual-Model Fabrication
by Ferdi Allaf, Meriç Arslan, Mustafa Özcan and Buket Erdem
Polymers 2026, 18(15), 1909; https://doi.org/10.3390/polym18151909 - 4 Aug 2026
Viewed by 337
Abstract
Thermoforming remains the predominant fabrication route for clear thermoplastic orthodontic appliances, yet it reduces and redistributes sheet thickness, which governs force delivered to teeth. Simultaneous thermoforming of two models may reduce fabrication time and material waste; however, its effect on final appliance thickness [...] Read more.
Thermoforming remains the predominant fabrication route for clear thermoplastic orthodontic appliances, yet it reduces and redistributes sheet thickness, which governs force delivered to teeth. Simultaneous thermoforming of two models may reduce fabrication time and material waste; however, its effect on final appliance thickness has not been evaluated. This in vitro study compared appliance thickness after thermoforming over a single model or two models simultaneously, using ten commercial aligner brands with different polymer composition and initial thickness. Thickness was measured with a digital caliper at anterior, canine and posterior sites, and analyzed using three-way ANOVA with Tukey post hoc tests. A significant three-way interaction (measurement point × number of models × brand; p < 0.001) was found. Significant single- versus dual-model differences emerged in some brand–region combinations; in most, dual-model appliances were thicker than single-model appliances. Four brands showed no significant difference at any site. Within the limits of this study, simultaneous fabrication of two appliances in a single thermoforming cycle produced appliances with thicknesses comparable to, and often slightly greater than, those fabricated over a single model. Simultaneous thermoforming maintained comparable appliance thickness and may improve manufacturing efficiency. Full article
(This article belongs to the Section Polymer Applications)
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23 pages, 9332 KB  
Article
Response of Mechanical Properties in PVC-P GMB to Tensile Rate and Low Temperature
by Xinyan Li, Zhenxue Zhu, Jian Sun and Xianlei Zhang
Polymers 2026, 18(15), 1908; https://doi.org/10.3390/polym18151908 - 3 Aug 2026
Viewed by 293
Abstract
Plasticized polyvinyl chloride (PVC-P) geomembranes (GMBs) are widely used in cold regions as impervious barriers, facing combined low-temperature and variable loading effects. However, design specifications rely on room-temperature tests at fixed rates, not reflecting actual conditions. This study systematically investigates the axial tensile [...] Read more.
Plasticized polyvinyl chloride (PVC-P) geomembranes (GMBs) are widely used in cold regions as impervious barriers, facing combined low-temperature and variable loading effects. However, design specifications rely on room-temperature tests at fixed rates, not reflecting actual conditions. This study systematically investigates the axial tensile properties of a 1.5 mm thick PVC-P GMB across eight temperatures (−40 °C to 20 °C) and five tensile rates (1–100 mm/min). A total of 211 uniaxial tensile tests were conducted using a low-temperature system with a servo-hydraulic machine and DIC extensometer. Nominal and true stress–strain curves were analyzed. Results show that fracture strength, fracture strain, and elastic modulus are highly sensitive to temperature and tensile rate, with a pronounced coupling effect between these two factors. Lower temperatures increase fracture strength and elastic modulus but reduce fracture strain, leading to brittle transition at −40 °C, especially at high rates. The fracture strength, fracture strain, and elastic modulus all increased with tensile rates at low tensile rates (1–20 mm/min). However, negligible difference in these parameters at high rates (20–100 mm/min) was observed. Elastic modulus follows a Boltzmann function with temperature, and fracture strain linearly correlates with temperature (R2 > 0.93). The mechanical properties measured at room temperature overestimate the deformability at low-temperature and hence underestimate the brittle failure risk. Therefore, future cold-region testing should adopt tensile rates of 10 or 20 mm/min, and temperature-rate coupled constitutive models should be developed. These findings provide essential data and guidance for material selection, design, and standard revision for PVC-P GMBs in cold-region applications. Full article
(This article belongs to the Section Polymer Applications)
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26 pages, 9936 KB  
Article
Sustainable Valorization of Agro-Industrial Waste and Polymer Residues for High-Plasticity Clay Stabilization: An Agro-Rubber Hybrid Approach
by Fahad Alshawmar, Bisma Khalid, Sana Ullah, Waqas Hassan, Mudassir Mehmood and Sofia Sarwar
Polymers 2026, 18(15), 1907; https://doi.org/10.3390/polym18151907 - 3 Aug 2026
Viewed by 341
Abstract
Expansive soils, characterized by pronounced volumetric instability under moisture fluctuations, pose a persistent challenge to the safety, serviceability, and long-term stability of civil infrastructure. In response to these challenges, increasing attention has been directed toward the use of sustainable waste-derived additives as environmentally [...] Read more.
Expansive soils, characterized by pronounced volumetric instability under moisture fluctuations, pose a persistent challenge to the safety, serviceability, and long-term stability of civil infrastructure. In response to these challenges, increasing attention has been directed toward the use of sustainable waste-derived additives as environmentally responsible alternatives for improving problematic soils. This study investigates the mechanical behavior of expansive soil stabilized with waste eggshell powder (ESP) and recycled tire powder (RTP), an elastic polymeric waste material rich in rubber and carbon black derived from discarded tires. A comprehensive experimental program was conducted to evaluate the combined effects of ESP/RTP on soil performance. For this purpose, Atterberg’s limits, compaction, unconfined compressive strength (UCS), Swell potential, and California bearing ratio (CBR) tests were performed on untreated soil and soil modified with up to 25% ESP and 9% RTP. The experimental findings revealed that the incorporation of ESP and RTP significantly reduced the Atterberg limits, optimum moisture content (OMC), and swelling potential of the soil, with the optimum blend of 20% ESP and 6% RTP yielding the most pronounced overall improvement. Such changes signify a considerable reduction in soil plasticity and expansive susceptibility, thereby enhancing the volumetric stability of the treated soil. At the same time, maximum dry density (MDD), UCS, and CBR values increased appreciably, demonstrating improved compaction behavior, greater mechanical resistance, and superior load-bearing performance. Moreover, one-way ANOVA confirmed that the enhancements in UCS and CBR achieved at the optimum mix proportions were statistically significant at the 95% confidence level. Overall, the findings demonstrate that ESP and RTP can serve as a sustainable, cost-effective, and environmentally friendly stabilization solution for improving the engineering performance of expansive soils. Full article
(This article belongs to the Special Issue Polymers in the Face of Sustainable Development)
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21 pages, 4649 KB  
Article
Long-Term Osteochondral Repair Induced by Electrospun PLA/PCL Scaffolds Functionalized with Polypyrrole and Aggrecan: Histological and Mechanical Evaluation in a Rabbit Model
by Nancy C. Islas-Arteaga, Atlántida M. Raya-Rivera, Juan Morales-Corona, Diego R. Esquiliano-Rendon, Patricia G. Ontiveros-Nevares, Omar E. Uribe-Juárez, Roberto Olayo and María G. Flores Sánchez
Polymers 2026, 18(15), 1906; https://doi.org/10.3390/polym18151906 - 3 Aug 2026
Viewed by 361
Abstract
Articular cartilage possesses a limited intrinsic repair capacity, and current treatment strategies frequently result in fibrocartilaginous repair tissue with inferior structural and mechanical properties compared with native hyaline cartilage. Increasing evidence indicates that successful restoration of joint function requires regeneration of the entire [...] Read more.
Articular cartilage possesses a limited intrinsic repair capacity, and current treatment strategies frequently result in fibrocartilaginous repair tissue with inferior structural and mechanical properties compared with native hyaline cartilage. Increasing evidence indicates that successful restoration of joint function requires regeneration of the entire osteochondral unit and adequate integration between cartilage and subchondral bone. Cartilage tissue engineering has emerged as an effective approach for repairing damaged cartilage. The present study evaluated the long-term performance of electrospun PLA/PCL (70/30) scaffolds coated with iodine-doped polypyrrole (PPy-I), with and without aggrecan incorporation, in a rabbit osteochondral defect model after 12 months of implantation. Two scaffold formulations were evaluated: M1 (PLA-PCL-PPy-I) and M2 (PLA-PCL-PPy-I-AG), each implanted either without cells or after in vitro pre-culture with autologous chondrocytes prior to implantation. Histological analyses were performed to assess tissue organization and osteochondral integration, while indentation testing was used to characterize the mechanical behavior of the regenerated tissues. Experimental force–displacement data were further analyzed using a generalized nonlinear Maxwell viscoelastic model. Histological evaluation revealed that scaffold composition and cellularization influenced the characteristics of the regenerated tissue. The M2 scaffold pre-cultured with autologous chondrocytes exhibited the structural organization most closely resembling native hyaline cartilage, including a tri-zonal architecture and a continuous tidemark indicative of improved osteochondral integration. Mechanical testing demonstrated nonlinear viscoelastic behavior and hysteresis in both regenerated and native tissues. The proposed generalized nonlinear Maxwell viscoelastic model provides a practical framework for the mechanical characterization of regenerated osteochondral tissues using only two effective parameters representing the elastic and viscous response, and may support future studies aimed at estimating their intrinsic mechanical properties. Full article
(This article belongs to the Special Issue Advances in Electrospun Polymeric Nanofibers)
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28 pages, 906 KB  
Review
Lignin-Based Adhesives for Various Packaging Applications
by Urška Klenovšek and Urška Vrabič-Brodnjak
Polymers 2026, 18(15), 1905; https://doi.org/10.3390/polym18151905 - 3 Aug 2026
Viewed by 429
Abstract
Growing demand for more sustainable packaging has increased interest in bio-based adhesives as alternatives to conventional fossil-derived systems. Among renewable raw materials, lignin is particularly attractive because of its aromatic structure, phenolic functionality, and availability as a side stream of pulp, paper, and [...] Read more.
Growing demand for more sustainable packaging has increased interest in bio-based adhesives as alternatives to conventional fossil-derived systems. Among renewable raw materials, lignin is particularly attractive because of its aromatic structure, phenolic functionality, and availability as a side stream of pulp, paper, and biorefinery processes. This review critically examines the potential of lignin-based adhesives for packaging applications. Selected polysaccharide-, protein-, vegetable-oil-, and tannin-based systems are briefly discussed as comparative references, while the main focus is placed on the properties of kraft lignin, lignosulfonates, organosolv lignin, and soda lignin. Their structural differences, adhesive behaviour, and suitability for chemical modification through hydroxymethylation, phenolation, demethylation, depolymerization, oxidation, and epoxidation are evaluated. Because most lignin-adhesive research concerns wood bonding, the transferability of these findings to paper, paperboard, labels, coatings, films, and hot-melt packaging adhesives is critically assessed. Direct evidence for packaging applications remains limited, although existing studies demonstrate promising opportunities for paper bonding, pressure-sensitive systems, and paperboard hot-melt adhesives. Key challenges include lignin heterogeneity, processing complexity, moisture resistance, colour, food-contact safety, scalability, and compatibility with recycling. Full article
(This article belongs to the Special Issue Recent Advances in Biobased and Biodegradable Polymer Materials for Packaging Applications)
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26 pages, 6641 KB  
Article
High-Efficiency Adsorption of PS, PE, and PP Microplastics from Environmental Waters Using a Cross-Linked Chitosan/Graphitic Carbon Nitride/ZIF-67 Nanocomposite
by Amr A. Yakout and Faten M. Ali Zainy
Polymers 2026, 18(15), 1904; https://doi.org/10.3390/polym18151904 - 3 Aug 2026
Viewed by 435
Abstract
Municipal wastewater is a major pathway for the continuous release of microplastics into aquatic environments, making the development of efficient and reusable capture materials essential for advanced water treatment. In this study, a multifunctional ZIF-67/g-C3N4/CS nanocomposite was [...] Read more.
Municipal wastewater is a major pathway for the continuous release of microplastics into aquatic environments, making the development of efficient and reusable capture materials essential for advanced water treatment. In this study, a multifunctional ZIF-67/g-C3N4/CS nanocomposite was designed by integrating cobalt-based zeolitic imidazolate framework ZIF-67 with graphitic carbon nitride (g-C3N4) and a chitosan (CS) biopolymer matrix. The novelty of this material lies in combining the high porosity and tunable surface chemistry of ZIF-67, the π-rich layered structure of g-C3N4, and the hydrophilic, amino-rich chitosan framework into a single adsorptive platform for simultaneous removal of chemically different microplastics. The nanocomposite achieved high removal efficiencies for polystyrene (PS), polypropylene (PP), and polyethylene (PE) microplastics with particle sizes of 20–25 μm, reaching 97.4%, 92.1%, and 90.3%, respectively, at pH 7.6 within 25 min. The higher affinity toward PS is attributed to additional π–π interactions between the aromatic PS chains and the conjugated domains of g-C3N4/ZIF-67, whereas PP and PE removal is mainly governed by hydrophobic adhesion, surface trapping, and interfacial interactions with the chitosan-supported porous framework. The equilibrium data were well described by both Langmuir and Freundlich models, with maximum adsorption capacities of 97.69, 94.86, and 93.67 mg g−1 for PS, PP, and PE, respectively. The nanocomposite retained high recyclability, maintaining 95–97 ± 3.1% removal after five adsorption–desorption cycles. These findings demonstrate that ZIF-67/g-C3N4/CS is a durable and high-performance adsorbent for microplastic remediation, with strong potential for application in municipal wastewater treatment, constructed wetlands, and advanced water-polishing systems. Full article
(This article belongs to the Special Issue Polymer Materials for Ecological and Environmental Applications)
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21 pages, 4423 KB  
Article
Valorization of Sunflower Seed Husks into Cellulose Nanofibrils and Nanocrystals for Sustainable Hydrogel Adsorbents in Heavy Metal Removal
by Ainur K. Battalova, Kydyrmolla Akatan, Ansagan Demeukhan, Esbol Shaimardan, Nariman R. Kaiyrbekov, Zhandos R. Sagdollin, Ainur K. Kabdrakhmanova, Sana K. Kabdrakhmanova, Bhanumathyamma Deepa and Sabu Thomas
Polymers 2026, 18(15), 1903; https://doi.org/10.3390/polym18151903 - 3 Aug 2026
Cited by 1 | Viewed by 481
Abstract
The application of cellulose-based nanocomposite sorbents as environmentally friendly materials for water purification has emerged as an important and rapidly developing research area. In this context, cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) were successfully extracted from microcrystalline cellulose (MCC) derived from sunflower [...] Read more.
The application of cellulose-based nanocomposite sorbents as environmentally friendly materials for water purification has emerged as an important and rapidly developing research area. In this context, cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) were successfully extracted from microcrystalline cellulose (MCC) derived from sunflower seed husks (SFHs) and comprehensively characterized. The obtained nanocellulosic materials were subsequently utilized to fabricate nanocomposite hydrogels, designated as HGCNF and HGCNC. The results revealed distinct structural and physicochemical characteristics of CNFs and CNCs, which significantly affected the morphology, swelling behavior, and stability of the resulting hydrogels. Swelling experiments conducted under various environmental conditions demonstrated that HGCNF exhibited higher water uptake and swelling capacity than HGCNC. Both hydrogels showed maximum swelling under near-neutral conditions (pH ≈ 6.5) and exhibited pronounced sensitivity to changes in ionic strength and solvent polarity. Furthermore, adsorption studies confirmed the effective removal of Cu2+ ions by both hydrogels, with HGCNC exhibiting a slightly higher adsorption capacity than HGCNF; the degree of sorption was 51.5%. These findings demonstrate that nanocellulose-based hydrogels possess tunable physicochemical properties and considerable potential as sustainable sorbent materials for water treatment, while also offering promising applications in environmental remediation, controlled drug delivery, and biomedical engineering. Full article
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17 pages, 2866 KB  
Article
Photo–Thermally Sequentially Responsive Shape Memory Polymers Based on Side–Chain Azobenzene–Functionalized Epoxy
by Jinxiong Wen, Xianhao Mao, Shaojun Chen, Yuanyuan Li, Zhiwen Tu, Huilin Lai and Haitao Zhuo
Polymers 2026, 18(15), 1902; https://doi.org/10.3390/polym18151902 - 3 Aug 2026
Viewed by 596
Abstract
To address the critical limitations of traditional photothermal–responsive epoxy–based shape memory polymers (ESMPs), such as poor compatibility and cyclical instability, a series of side–chain azobenzene (Azo)–functionalized linear ESMPs (EPDm) were successfully synthesized via chemical bonding. Highly rigid 4–aminoazobenzene (Azodm) units were covalently integrated [...] Read more.
To address the critical limitations of traditional photothermal–responsive epoxy–based shape memory polymers (ESMPs), such as poor compatibility and cyclical instability, a series of side–chain azobenzene (Azo)–functionalized linear ESMPs (EPDm) were successfully synthesized via chemical bonding. Highly rigid 4–aminoazobenzene (Azodm) units were covalently integrated into the Bisphenol A–type epoxy backbone as functional photo–responsive side chains. Systematic characterizations confirmed that the glass transition temperature (Tg) of the EPDm polymers could be precisely tuned from 41.53 °C to 53.26 °C by adjusting the Azodm content. Benefiting from the proposed homogeneous covalent architecture, the EPDm films exhibited superior photothermal sequential behavior and remarkable shape memory stability despite a slight reduction in tensile strength (≈10–12 MPa). Under 365 nm UV irradiation, the pre–stretched EPDm10 specimen achieved a rapid macroscopic bending angle of over 150° within 15 s, driven exclusively by the trans–to–cis molecular photoisomerization of the Azo side chains well below the matrix Tg. Furthermore, standard shape memory cycles demonstrated excellent shape fixity (Rf > 98%) and recovery (Rr > 95%) ratios, alongside exceptional anti–fatigue performance with minimal strain variance (≈5%) over consecutive cycles. This work establishes a robust and high–efficiency molecular design strategy for photo–thermally sequentially responsive shape memory polymers, offering immense potential for smart actuators and flexible electronics. Full article
(This article belongs to the Special Issue Shape Memory Polymer Materials, 2nd Edition)
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18 pages, 12073 KB  
Article
Synergistic Flow Field and Ion–Dipole Interactions Enable γ-β Phase Transformation in Poly(vinylidene fluoride)
by Qian Wang, Hong-Biao Yin, Hua-Jian Li, Xiang Bai, Fei Wang, Jianguo Liang, Guo-Zhen Ma, Jia-Yi Ren and Zhanchun Chen
Polymers 2026, 18(15), 1901; https://doi.org/10.3390/polym18151901 - 3 Aug 2026
Viewed by 542
Abstract
Poly(vinylidene fluoride) (PVDF) exhibits excellent piezoelectric properties governed by the content and orientation of its polar phases. Herein, a synergistic regulation strategy integrating a flow field induced by a designed solid-phase extrusion die and ion–dipole interactions introduced by CTAB is established to achieve [...] Read more.
Poly(vinylidene fluoride) (PVDF) exhibits excellent piezoelectric properties governed by the content and orientation of its polar phases. Herein, a synergistic regulation strategy integrating a flow field induced by a designed solid-phase extrusion die and ion–dipole interactions introduced by CTAB is established to achieve highly oriented β phase in PVDF. The incorporation of CTAB promotes the formation of the γ phase before extrusion, providing a structurally favorable precursor for the subsequent flow-induced γ-β phase transformation. During solid-phase extrusion, the converging flow field drives extensive molecular chain alignment, promoting the γ-β phase transformation and substantially enhancing both β phase content and orientation. The synergistic effects of CTAB-induced ion–dipole interactions and the converging flow field further regulate the melting behavior and crystal perfection of PVDF, driving the transformation of the lamellar structure into highly oriented lamellar bundles along the extrusion direction. Among all compositions studied, the blends containing 5 wt% CTAB exhibit the optimal polar phase content and orientation characteristics, along with the highest dielectric constant. This work elucidates the synergistic regulation of PVDF hierarchical structures by ion–dipole interactions and flow fields, offering an effective strategy for fabricating high-performance piezoelectric PVDF materials. Full article
(This article belongs to the Section Polymer Chemistry)
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12 pages, 8896 KB  
Article
Backbone Engineering of Polythiophenes via Quinoid and Cyano Dual Functionalization for n-Type Polymers
by Weipeng Sun, Yanlin Wei, Peng Wang, Dingqin Hu, Peng Dai, Wenge Zhang, Dian Zhang, Jianfeng Li, Yongqiang Shi and Xugang Guo
Polymers 2026, 18(15), 1900; https://doi.org/10.3390/polym18151900 - 3 Aug 2026
Viewed by 392
Abstract
Developing high-performance n-type polymer semiconductors is hindered by the scarcity of strong electron-deficient building blocks. Herein, we report a dual-functionalization strategy that integrates both quinoid and cyano groups into polythiophene backbones to construct n-type polymers. Two new polymers, PQTTCN and PQTVTCN, were synthesized [...] Read more.
Developing high-performance n-type polymer semiconductors is hindered by the scarcity of strong electron-deficient building blocks. Herein, we report a dual-functionalization strategy that integrates both quinoid and cyano groups into polythiophene backbones to construct n-type polymers. Two new polymers, PQTTCN and PQTVTCN, were synthesized via the Stille copolymerization of a thienoquinoid-based dibrominated monomer (TTD2T-Br) with cyano-functionalized bithiophene and thienylene-vinylene-thienylene distannyl monomers, respectively. Electrochemical and computational analyses confirm that both polymers exhibit low-lying LUMO levels of −4.07 eV and highly planar backbones. In organic field-effect transistors, PQTTCN and PQTVTCN show unipolar n-type charge transport, with electron mobilities of 0.036 and 0.002 cm2 V−1 s−1, respectively, which are attributed to their deep frontier molecular orbitals and planar conformations. Upon doping, both polymers exhibit n-type thermoelectric performance, achieving an electrical conductivity and power factor values of 0.16 S cm−1 and 0.75 μW m−1 K−2 for PQTTCN and 0.043 S cm−1 and 0.17 μW m−1 K−2 for PQTVTCN, respectively. AFM and GIWAXS results demonstrate that PQTTCN has better dopant compatibility and higher crystallinity than PQTVTCN. This work highlights that the combination of quinoid and cyano units offers a promising strategy for developing high-performance n-type polymer semiconductors for organic electronics. Full article
(This article belongs to the Topic Advanced Materials for Flexible and Wearable Electronics)
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