Polymers

17 pages, 3986 KiB

Open AccessArticle

Titanate-Coupled Aluminum as an Interfacial Modifier for Enhanced Thermal and Mechanical Performance in Hybrid Epoxy Composites

by Hai-Long Cheng, Seul-Yi Lee, Na Chu, Se-Yeol Lee, Fan-Long Jin and Soo-Jin Park

Polymers 2025, 17(14), 1922; https://doi.org/10.3390/polym17141922 - 11 Jul 2025

Abstract

Thermally conductive polymer composites are essential for effective heat dissipation in electronic packaging, where both thermal management and mechanical reliability are critical. Although diglycidyl ether of bisphenol-A (DGEBA)-based epoxies exhibit favorable properties, their intrinsically low thermal conductivity limits broader applications. Incorporating conductive fillers, [...] Read more.

Thermally conductive polymer composites are essential for effective heat dissipation in electronic packaging, where both thermal management and mechanical reliability are critical. Although diglycidyl ether of bisphenol-A (DGEBA)-based epoxies exhibit favorable properties, their intrinsically low thermal conductivity limits broader applications. Incorporating conductive fillers, such as expanded graphite (EG) and metal powders, enhances heat transport but often compromises mechanical strength due to poor filler–matrix compatibility. In this study, we address this trade-off by employing a titanate coupling agent to surface-modify aluminum (Al) fillers, thereby improving interfacial adhesion and dispersion within the DGEBA matrix. Our results show that incorporating 10 wt% untreated Al increases thermal conductivity from 7.35 to 9.60 W/m·K; however, this gain comes at the cost of flexural strength, which drops to 18.29 MPa. In contrast, titanate-modified Al (Ti@Al) not only preserves high thermal conductivity but also restores mechanical performance, achieving a flexural strength of 35.31 MPa (at 5 wt% Ti@Al) and increasing impact strength from 0.60 to 1.01 kJ/m². These findings demonstrate that interfacial engineering via titanate coupling offers a compelling strategy to overcome the thermal–mechanical trade-off in hybrid composites, enabling the development of high-performance materials for advanced thermal interface and structural applications. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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29 pages, 2673 KiB

Open AccessArticle

Process Parameters Optimization and Mechanical Properties of Additively Manufactured Ankle–Foot Orthoses Based on Polypropylene

by Sahar Swesi, Mohamed Yousfi, Nicolas Tardif and Abder Banoune

Polymers 2025, 17(14), 1921; https://doi.org/10.3390/polym17141921 - 11 Jul 2025

Abstract

Nowadays, Fused Filament Fabrication (FFF) 3D printing offers promising opportunities for the customized manufacturing of ankle–foot orthoses (AFOs) targeted towards rehabilitation purposes. Polypropylene (PP) represents an ideal candidate in orthotic applications due to its light weight and superior mechanical properties, offering an excellent [...] Read more.

Nowadays, Fused Filament Fabrication (FFF) 3D printing offers promising opportunities for the customized manufacturing of ankle–foot orthoses (AFOs) targeted towards rehabilitation purposes. Polypropylene (PP) represents an ideal candidate in orthotic applications due to its light weight and superior mechanical properties, offering an excellent balance between flexibility, chemical resistance, biocompatibility, and long-term durability. However, Additive Manufacturing (AM) of AFOs based on PP remains a major challenge due to its limited bed adhesion and high shrinkage, especially for making large parts such as AFOs. The primary innovation of the present study lies in the optimization of FFF 3D printing parameters for the fabrication of functional, patient-specific orthoses using PP, a material still underutilized in the AM of medical devices. Firstly, a thorough thermomechanical characterization was conducted, allowing the implementation of a (thermo-)elastic material model for the used PP filament. Thereafter, a Taguchi design of experiments (DOE) was established to study the influence of several printing parameters (extrusion temperature, printing speed, layer thickness, infill density, infill pattern, and part orientation) on the mechanical properties of 3D-printed specimens. Three-point bending tests were conducted to evaluate the strength and stiffness of the samples, while additional tensile tests were performed on the 3D-printed orthoses using a home-made innovative device to validate the optimal configurations. The results showed that the maximum flexural modulus of 3D-printed specimens was achieved when the printing speed was around 50 mm/s. The most significant parameter for mechanical performance and reduction in printing time was shown to be infill density, contributing 73.2% to maximum stress and 75.2% to Interlaminar Shear Strength (ILSS). Finally, the applicability of the finite element method (FEM) to simulate the FFF process-induced deflections, part distortion (warpage), and residual stresses in 3D-printed orthoses was investigated using a numerical simulation tool (Digimat-AM^®). The combination of Taguchi DOE with Digimat-AM for polypropylene AFOs highlighted that the 90° orientation appeared to be the most suitable configuration, as it minimizes deformation and von Mises stress, ensuring improved quality and robustness of the printed orthoses. The findings from this study contribute by providing a reliable method for printing PP parts with improved mechanical performance, thereby opening new opportunities for its use in medical-grade additive manufacturing. Full article

(This article belongs to the Special Issue Latest Progress in the Additive Manufacturing of Polymeric Materials)

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19 pages, 4534 KiB

Open AccessArticle

Error Modeling and Error Control Study of PA/Pine Wood Biomass Composites

by Jiaming Dai, Yanling Guo and Haoyu Zhang

Polymers 2025, 17(14), 1920; https://doi.org/10.3390/polym17141920 - 11 Jul 2025

Abstract

Laser sintering (LS) technology is one of the most widely commercialized additive manufacturing technologies. However, the popularization of LS technology in civilian applications has long been constrained by accuracy-related issues. Polyamide (PA), as the most mature LS material, still faces challenges in controlling [...] Read more.

Laser sintering (LS) technology is one of the most widely commercialized additive manufacturing technologies. However, the popularization of LS technology in civilian applications has long been constrained by accuracy-related issues. Polyamide (PA), as the most mature LS material, still faces challenges in controlling part dimensional errors. Biomass materials, when used as fillers, can improve the printing accuracy of fabricated parts, demonstrating a technically feasible synergy between PA and biomass materials. Therefore, this study analyzes the fundamental material properties of PA/pine biomass composites and investigates error control methods for LS-fabricated parts using PA/biomass materials as feedstock. This study investigates the error modeling of LS-fabricated parts from two perspectives. First, a theoretical mathematical model is established to predict part errors by incorporating material properties, process parameters, and equipment factors. Second, a data-driven model is developed using BP neural network technology based on experimental data to correlate LS process parameters with part dimensional errors. Additionally, the predictive capabilities and compensation effects of both models are examined. The experimental results indicate that the nylon/pine wood biomass composite with a pine wood content of 3 wt% can produce molded parts with a tensile strength of 20 MPa. Additionally, this material exhibits a sintering preheating window range of 10 °C, which facilitates the production of parts with both favorable mechanical properties and dimensional accuracy. Both error prediction models are capable of predicting the dimensional deviations of the parts. The data-driven model demonstrates superior deviation prediction accuracy (approximately 81–91%) for LS parts compared to the theoretical mathematical model (approximately 62–73%). By applying compensation based on the error prediction models, the overall dimensional deviation can be reduced from 1.61–3.49% to 0.41–0.50%. Consequently, the part’s precision grade (according to ISO 2768) is improved from below Grade V to Grade C. Full article

(This article belongs to the Special Issue Wood and Wood-Based Composites: New Frontiers in Modification, Performance, and Sustainability)

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20 pages, 2364 KiB

Open AccessArticle

Novel Core–Shell Aerogel Formulation for Drug Delivery Based on Alginate and Konjac Glucomannan: Rational Design Using Artificial Intelligence Tools

by Carlos Illanes-Bordomás, Mariana Landin and Carlos A. García-González

Polymers 2025, 17(14), 1919; https://doi.org/10.3390/polym17141919 - 11 Jul 2025

Abstract

This study explores novel alginate–konjac glucomannan core–shell aerogel particles for drug delivery systems fabricated via air-assisted coaxial prilling. A systematic approach is needed for the optimization of this method due to the numerous processing variables involved. This study investigated the influence of six [...] Read more.

This study explores novel alginate–konjac glucomannan core–shell aerogel particles for drug delivery systems fabricated via air-assisted coaxial prilling. A systematic approach is needed for the optimization of this method due to the numerous processing variables involved. This study investigated the influence of six variables: alginate and konjac glucomannan concentrations, compressed airflow, liquid pump pressures, and nozzle configuration. A hybrid software using Artificial Neural Networks and genetic algorithms was used to model and optimize the hydrogel formation, achieving a 100% desirable solution. The optimal formulation identified resulted in particles displaying a log-normal size distribution (R² = 0.967) with an average diameter of 1.57 mm. Supercritical CO₂ drying yielded aerogels with macropores and mesopores and a high specific surface area (201 ± 10 m²/g). The loading of vancomycin hydrochloride (Van) or a dexamethasone base (DX) into the aerogel cores during the process was tested. The aerogels exhibited appropriate structural characteristics, and both drugs showed burst release profiles with ca. 80% release within 10 min for DX and medium-dependent release for Van. This study demonstrates the feasibility of producing konjac aerogel particles for delivery systems and the high potential of AI-driven optimization methods, highlighting the need for coating modifications to achieve the desired release profiles. Full article

(This article belongs to the Special Issue Biopolymers for Medical Applications: From Drug Delivery to Tissue Engineering)

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20 pages, 3330 KiB

Open AccessArticle

Impact of Multiple Mechanical Recycling Cycles via Semi-Industrial Twin-Screw Extrusion on the Properties of Polybutylene Succinate (PBS)

by Vito Gigante, Laura Aliotta, Luigi Botta, Irene Bavasso, Alessandro Guzzini, Serena Gabrielli, Fabrizio Sarasini, Jacopo Tirillò and Andrea Lazzeri

Polymers 2025, 17(14), 1918; https://doi.org/10.3390/polym17141918 - 11 Jul 2025

Abstract

This study investigates the effects of repeated mechanical recycling on the structural, thermal, mechanical, and aesthetic properties of poly(butylene succinate) (PBS), a commercially available bio-based and biodegradable aliphatic polyester. PBS production scraps were subjected to five consecutive recycling cycles through semi-industrial extrusion compounding [...] Read more.

This study investigates the effects of repeated mechanical recycling on the structural, thermal, mechanical, and aesthetic properties of poly(butylene succinate) (PBS), a commercially available bio-based and biodegradable aliphatic polyester. PBS production scraps were subjected to five consecutive recycling cycles through semi-industrial extrusion compounding followed by injection molding to simulate realistic mechanical reprocessing conditions. Melt mass-flow rate (MFR) analysis revealed a progressive increase in melt fluidity. Initially, the trend of viscosity followed the melt flow rate; however, increasing the reprocessing number (up to 5) resulted in a partial recovery of viscosity, which was caused by chain branching mechanisms. The phenomenon was also confirmed by data of molecular weight evaluation. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed the thermal stability of the polymer, with minimal shifts in glass transition, crystallization, and degradation temperatures during the reprocessing cycles. Tensile tests revealed a slight reduction in strength and stiffness, but an increase in elongation at break, indicating improved ductility. Impact resistance declined moderately from 8.7 to 7.3 kJ/m² upon reprocessing; however, it exhibited a pronounced reduction to 1.8 kJ/m² at −50 °C, reflecting brittle behavior under sub-ambient conditions. Despite these variations, PBS maintained excellent color stability (ΔE < 1), ensuring aesthetic consistency while retaining good mechanical and thermal properties. Full article

(This article belongs to the Special Issue Modeling and Characterization of Recycled High-Performance Polymer Materials)

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12 pages, 2558 KiB

Open AccessArticle

Multi-Walled Carbon Nanotube (MWCNT)-Reinforced Polystyrene (PS) Composites: Preparation, Structural Analysis, and Mechanical and Thermal Properties

by Kadir Gündoğan and Damla Karaağaç

Polymers 2025, 17(14), 1917; https://doi.org/10.3390/polym17141917 - 11 Jul 2025

Abstract

Polystyrene (PS), a thermoplastic polymer, is used in many applications due to its mechanical performance, good chemical inertness, and excellent processability. However, it is doped with different nanomaterials for reasons such as improving its electrical conductivity and mechanical properties. In this study, carbon [...] Read more.

Polystyrene (PS), a thermoplastic polymer, is used in many applications due to its mechanical performance, good chemical inertness, and excellent processability. However, it is doped with different nanomaterials for reasons such as improving its electrical conductivity and mechanical properties. In this study, carbon nanotube (CNT)-added PS composites were produced with the aim of combining the properties of CNTs, such as their low weight and high tensile strength and Young’s modulus, with the versatility, processability, and mechanical properties of PS. In this study, multi-walled carbon nanotube (MWCNT)-reinforced polystyrene (PS) composites with different percentage ratios (0.1, 0.2, and 0.3 wt%) were prepared by a plastic injection molding method. The mechanical, microstructural, and thermal properties of the fabricated PS/MWCNT composites were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy, Atomic Force Microscopy (AFM) and Thermogravimetric Analysis (TGA) techniques. AFM analyses were carried out to investigate the surface properties of MWCNT-reinforced composite materials by evaluating the root mean square (RMS) values. These analyses show that the RMS value for MWCNT-reinforced composite materials decreases as the weight percentage of MWCNTs increases. The TGA results show that there is no change in the degradation temperature of the 0.1%- and 0.2%-doped MWCNT composites compared to pure polystyrene, but the degradation of the 0.3%-doped MWCNT composite is almost complete at a temperature of 539 °C. Among the PS/MWCNT composites, the 0.3%-doped MWCNT composite exhibits more thermal stability than pure PS and other composites. Similarly, the values of the percentage elongation and tensile strength of 0.3% MWCNT-doped composites was obtained as 1.91% and 12.174% mm², respectively. These values are higher than the values of 0.1% and 0.2% MWCNT-doped composite materials. In conclusion, the mechanical and thermal properties of MWCNT-reinforced PS polymers provide promising results for researchers working in this field. Full article

(This article belongs to the Topic Advanced Carbon Fiber Reinforced Composite Materials, Volume II)

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15 pages, 4602 KiB

Open AccessArticle

Antifungal Nanocomposites from Honeybee Chitosan and Royal Jelly-Mediated Nanosilver for Suppressing Biofilm and Hyphal Formation of Candida albicans

by Mousa Abdullah Alghuthaymi

Polymers 2025, 17(14), 1916; https://doi.org/10.3390/polym17141916 - 11 Jul 2025

Abstract

Candida albicans complications challenged researchers and health overseers to discover effectual agents for suppressing such yeast growth, biofilm formation and conversion to hyphal form. The nanomaterials and their composites provided extraordinary bioactivities and functionalities as antimicrobial preparations. The extraction of chitosan (BCt) from [...] Read more.

Candida albicans complications challenged researchers and health overseers to discover effectual agents for suppressing such yeast growth, biofilm formation and conversion to hyphal form. The nanomaterials and their composites provided extraordinary bioactivities and functionalities as antimicrobial preparations. The extraction of chitosan (BCt) from honeybee corpuses was achieved as an innovative biopolymer for nanocomposite formation. The green (bio)synthesis of nanosilver (AgNPs) was promisingly performed using royal jelly (RJ) as a mediator of synthesis. The RJ-synthesized AgNPs had an average diameter of 3.61 nm and were negatively charged (−27.2 mV). The formulated nanocomposites from BCt/RJ/AgNPs at 2:1 (F1), 1:1 (F2), and 1:2 (F3) ratios had average diameters of 63.19, 27.65, and 52.74 nm, where their surface charges were +33.8, +29.3, and −11.5 mV, respectively. The infrared (FTIR) analysis designated molecules’ interactions, whereas the transmission microscopy emphasized the homogenous distribution and impedance of AgNPs within the biopolymers’ nanocomposites. Challenging C. albicans strains with nanomaterials/composites pinpointed their bioactivity for suppressing yeast growth and biofilm formation; the F2 nanocomposite exhibited superior actions, with the lowest inhibitory concentrations (MICs) of 125–175 mg/L, whereas the MIC ranges were 150–200 and 175–225 mg/L for F3 and F1, respectively. The different BCht/RJ/AgNP nanocomposites could entirely suppress the biofilm formation of all C. albicans strains. The scanning microscopy reflected the nanocomposite efficiency for C. albicans cell destruction and the complete suppression of hyphal formation. The application of generated BCht/RJ/AgNP nanocomposites is strongly recommended as they are effectual, natural and advanced materials for combating C. albicans pathogens. Full article

(This article belongs to the Special Issue Functional and Biocompatible Nanostructured Polymer Scaffolds for Therapeutic Applications)

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19 pages, 3806 KiB

Open AccessArticle

Electroactive Poly(amic acid) Films Grafted with Pendant Aniline Tetramer for Hydrogen Sulfide Gas Sensing Applications

by Kun-Hao Luo, Yun-Ting Chen, Hsuan-Yu Wu, Zong-Kai Ni and Jui-Ming Yeh

Polymers 2025, 17(14), 1915; https://doi.org/10.3390/polym17141915 - 11 Jul 2025

Abstract

Hydrogen sulfide (H₂S) is a highly toxic and corrosive gas generated in numerous industrial and environmental processes; rapid, sensitive detection at low ppm levels is therefore crucial for ensuring occupational safety and protecting public health. This work explores the effect of [...] Read more.

Hydrogen sulfide (H₂S) is a highly toxic and corrosive gas generated in numerous industrial and environmental processes; rapid, sensitive detection at low ppm levels is therefore crucial for ensuring occupational safety and protecting public health. This work explores the effect of grafting various loadings of pendant aniline tetramer pendants (PEDA) onto electroactive poly(amic acid) (EPAA) films and evaluates their performance as H₂S gas sensors. Comprehensive characterization including ion trap mass spectrometry (Ion trap MS), Fourier-transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and four-probe conductivity measurements, confirmed successful PEDA incorporation and revealed enhanced electrical conductivity with increasing PEDA content. Gas sensing tests revealed that EPAA3 (3 wt% PEDA) achieved the best overall performance toward 10 ppm H₂S, producing a 591% response with a rapid 108 s response time. Selectivity studies showed that the response of EPAA3 to H₂S exceeded those for SO₂, NO₂, NH₃, and CO by factors of five to twelve, underscoring its excellent discrimination against common interferents. Repeatability tests over five successive cycles gave a relative standard deviation of just 7.4% for EPAA3, and long-term stability measurements over 16 days in ambient air demonstrated that EPAA3 retained over 80%. These findings establish that PEDA-grafted PAA films combine the processability of poly(amic acid) with the sharp, reversible redox behavior of pendant aniline tetramers, delivering reproducible, selective, and stable H₂S sensing. EPAA3, in particular, represents a balanced composition that maximizes sensitivity and durability, offering a promising platform for practical environmental monitoring and industrial safety applications. Full article

(This article belongs to the Special Issue Development of Applications of Polymer-Based Sensors and Actuators)

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13 pages, 2269 KiB

Open AccessArticle

Sulfonated Biopolymer Derived from Wheat Straw for the Recovery of Au(III)

by Nyamjargal Lkhamtogmid, Burmaa Gunchin, Burmaa Dashdendev, Munkhbaatar Punsantsogvoo, Munkhpurev Bat-Amgalan and Ganchimeg Yunden

Polymers 2025, 17(14), 1914; https://doi.org/10.3390/polym17141914 - 11 Jul 2025

Abstract

This study investigates the potential of sulfuric acid modified wheat straw, polysaccharide-rich agricultural byproduct, as a low-cost adsorbent for the selective adsorption of Au(III) ions from aqueous solutions. The wheat straw was treated with concentrated sulfuric acid to enhance its surface properties and [...] Read more.

This study investigates the potential of sulfuric acid modified wheat straw, polysaccharide-rich agricultural byproduct, as a low-cost adsorbent for the selective adsorption of Au(III) ions from aqueous solutions. The wheat straw was treated with concentrated sulfuric acid to enhance its surface properties and functional groups, particularly sulfonic and oxygen-containing functional groups. Adsorption experiments were performed under various conditions, including acid concentrations ranging from 1.0 to 3.0 mol/L, contact times from 1 to 6 h, and initial Au(III) concentrations of 60.36, 90.0, and 150.0 mg/L. The highest adsorption efficiency, 99.0%, was achieved at an acid concentration of 1.0 mol/L. Furthermore, it was determined that an increase in the initial Au(III) concentration from 60.36 mg/L to 150.0 mg/L resulted in a 4.5 times increase in maximum adsorption capacity under optimal conditions. Kinetic modeling revealed that the adsorption process followed pseudo-second order kinetics, suggesting chemisorption as the rate-limiting step. Characterization techniques such as SEM/EDS, XRD, BET and XPS confirmed structural modification, surface sulfonating, and the successful adsorption and reduction of Au(III) to elemental gold (Au⁰) on the modified straw surface. This work demonstrates that modified wheat straw is a promising, effective, and low cost for the recovery of gold from low-concentration solutions and provides insight into the adsorption and reduction mechanisms at the molecular level. Full article

(This article belongs to the Special Issue Polysaccharides: From Synthesis to Applications)

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15 pages, 5712 KiB

Open AccessArticle

Synthesis of Magnetic Nanoparticle/Polymer Matrix Nanocomposites with Induced Magnetic Performance

by Anastasios C. Patsidis, Aikaterini Sanida, Georgia C. Manika, Sevasti Gioti, Georgios N. Mathioudakis, Nicholas Petropoulos, Athanasios Kanapitsas, Christos Tsonos, Thanassis Speliotis and Georgios C. Psarras

Polymers 2025, 17(14), 1913; https://doi.org/10.3390/polym17141913 - 10 Jul 2025

Abstract

In this work magnetic nanoparticles (Fe₃O₄, or ZnFe₂O₄, or SrFe₁₂O₁₉) and BaTiO₃ microparticles were embedded in an epoxy resin for the synthesis of three series of hybrid magnetic polymer nanocomposites. [...] Read more.

In this work magnetic nanoparticles (Fe₃O₄, or ZnFe₂O₄, or SrFe₁₂O₁₉) and BaTiO₃ microparticles were embedded in an epoxy resin for the synthesis of three series of hybrid magnetic polymer nanocomposites. Barium titanate content was kept constant, while magnetic phase content was varied. Fabricated specimens were structurally and morphologically characterized by employing scanning electron microscopy images and X-ray diffraction patterns. Results implied successful synthesis of the hybrid nanocomposites. The magnetic behavior of the pure magnetic nanoparticles and the fabricated nanocomposites was investigated via a Vibrating Sample Magnetometer. The magnetic performance of each type of magnetic phase (i.e., soft and hard) was induced in the nanocomposites, and magnetic performance is strengthened with the increase in magnetic phase content. Initial magnetization curves were used for the determination of mass magnetic susceptibility of all nanocomposites. Magnetic saturation and magnetic remanence have been found to follow a linear relationship with magnetic phase content, giving the opportunity to predict the system’s response in advance. Full article

(This article belongs to the Special Issue Polymers in Inorganic Chemistry: Synthesis and Applications)

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27 pages, 5530 KiB

Open AccessArticle

The Lipid- and Polysaccharide-Rich Extracellular Polymeric Substances of Rhodococcus Support Biofilm Formation and Protection from Toxic Hydrocarbons

by Anastasiia Krivoruchko, Daria Nurieva, Vadim Luppov, Maria Kuyukina and Irina Ivshina

Polymers 2025, 17(14), 1912; https://doi.org/10.3390/polym17141912 - 10 Jul 2025

Abstract

Extracellular polymeric substances (EPS) are multifunctional biopolymers that have significant biotechnological potential. In this study, forty-seven strains of Rhodococcus actinomycetes were screened for EPS production and the content of its main components: carbohydrates, lipids, proteins, and nucleic acids. The Rhodococcus strains produced lipid-rich [...] Read more.

Extracellular polymeric substances (EPS) are multifunctional biopolymers that have significant biotechnological potential. In this study, forty-seven strains of Rhodococcus actinomycetes were screened for EPS production and the content of its main components: carbohydrates, lipids, proteins, and nucleic acids. The Rhodococcus strains produced lipid-rich EPS (15.6 mg·L⁻¹ to 71.7 mg·L⁻¹) with carbohydrate concentrations varying from 0.6 mg·L⁻¹ to 58.2 mg·L⁻¹ and low amounts of proteins and nucleic acids. Biofilms of R. ruber IEGM 231 were grown on nitrocellulose filters in the presence of n-hexane, n-hexadecane, or diesel fuel. The distribution of β-polysaccharides, glycoconjugates, and proteins between cells and the extracellular matrix was examined using fluorescence microscopy. The observed release of β-polysaccharides into the biofilm matrix in the presence of n-hexane and diesel fuel was regarded as an adaptation to the assimilation of these toxic hydrocarbons by Rhodococcus cells. Atomic force microscopy of the dried EPS film revealed adhesion forces between 1.0 and 20.0 nN, while some sites were highly adhesive (F_a ≥ 20.0 nN). EPS biosynthetic genes were identified, with two glycosyltransferases correlating with an increase in carbohydrate production. The production of EPS by Rhodococcus cells exhibited strain-specific rather than species-specific patterns, reflecting a high genetic diversity of these bacteria. Full article

(This article belongs to the Special Issue Advances in Biocompatible and Biodegradable Polymers, 4th Edition)

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22 pages, 4000 KiB

Open AccessArticle

Structure-Properties Correlations of PVA-Cellulose Based Nanocomposite Films for Food Packaging Applications

by Konstantinos Papapetros, Georgios N. Mathioudakis, Dionysios Vroulias, Nikolaos Koutroumanis, George A. Voyiatzis and Konstantinos S. Andrikopoulos

Polymers 2025, 17(14), 1911; https://doi.org/10.3390/polym17141911 - 10 Jul 2025

Abstract

Bio-nanocomposites based on poly (vinyl alcohol) (PVA) and cellulosic nanostructures are favorable for active food packaging applications. The current study systematically investigates the mechanical properties, gas permeation, and swelling parameters of PVA composites with cellulose nanocrystals (CNC) or nano lignocellulose (NLC) fibers. Alterations [...] Read more.

Bio-nanocomposites based on poly (vinyl alcohol) (PVA) and cellulosic nanostructures are favorable for active food packaging applications. The current study systematically investigates the mechanical properties, gas permeation, and swelling parameters of PVA composites with cellulose nanocrystals (CNC) or nano lignocellulose (NLC) fibers. Alterations in these macroscopic properties, which are critical for food packaging applications, are correlated with structural information at the molecular level. Strong interactions between the fillers and polymer host matrix were observed, while the PVA crystallinity exhibited a maximum at ~1% loading. Finally, the orientation of the PVA nanocrystals in the uniaxially stretched samples was found to depend non-monotonically on the CNC loading and draw ratio. Concerning the macroscopic properties of the composites, the swelling properties were reduced for the D1 food simulant, while for water, a considerable decrease was observed only when high NLC loadings were involved. Furthermore, although the water vapor transmission rates are roughly similar for all samples, the CO₂, N₂, and O₂ gas permeabilities are low, exhibiting further decrease in the 1% and 1–5% loading for CNC and NLC composites, respectively. The mechanical properties were considerably altered as a consequence of the good dispersion of the filler, increased crystallinity of the polymer matrix, and morphology of the filler. Thus, up to ~50%/~170% enhancement of the Young’s modulus and up to ~20%/~50% enhancement of the tensile strength are observed for the CNC/NLC composites. Interestingly, the elongation at break is also increased by ~20% for CNC composites, while it is reduced by ~40% for the NLC composites, signifying the favorable/unfavorable interactions of cellulose/lignin with the matrix. Full article

(This article belongs to the Special Issue Cellulose and Its Composites: Preparation and Applications)

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32 pages, 9426 KiB

Open AccessArticle

Multi-Output Prediction and Optimization of CO₂ Laser Cutting Quality in FFF-Printed ASA Thermoplastics Using Machine Learning Approaches

by Oguzhan Der

Polymers 2025, 17(14), 1910; https://doi.org/10.3390/polym17141910 - 10 Jul 2025

Abstract

This research article examines the CO₂ laser cutting performance of Fused Filament Fabricated Acrylonitrile Styrene Acrylate (ASA) thermoplastics by analyzing the influence of plate thickness, laser power, and cutting speed on four quality characteristics: surface roughness (Ra), top kerf width (Top KW), [...] Read more.

This research article examines the CO₂ laser cutting performance of Fused Filament Fabricated Acrylonitrile Styrene Acrylate (ASA) thermoplastics by analyzing the influence of plate thickness, laser power, and cutting speed on four quality characteristics: surface roughness (Ra), top kerf width (Top KW), bottom kerf width (Bottom KW), and bottom heat-affected zone (Bottom HAZ). Forty-five experiments were conducted using five thickness levels, three power levels, and three cutting speeds. To model and predict these outputs, seven machine learning approaches were employed: Autoencoder, Autoencoder–Gated Recurrent Unit, Autoencoder–Long Short-Term Memory, Random Forest, Extreme Gradient Boosting (XGBoost), Support Vector Regression, and Linear Regression. Among them, XGBoost yielded the highest accuracy across all performance metrics. Analysis of Variance results revealed that Ra is mainly affected by plate thickness, Bottom KW by cutting speed, and Bottom HAZ by power, while Top KW is influenced by all three parameters. The study proposes an effective prediction framework using multi-output modeling and hybrid deep learning, offering a data-driven foundation for process optimization. The findings are expected to support intelligent manufacturing systems for real-time quality prediction and adaptive laser post-processing of engineering-grade thermoplastics such as ASA. This integrative approach also enables a deeper understanding of nonlinear dependencies in laser–material interactions. Full article

(This article belongs to the Section Polymer Composites and Nanocomposites)

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15 pages, 1414 KiB

Open AccessArticle

Metal-Free A₂/B₂-Type Azide–Alkyne Polyaddition: Effect of Azides Structure on Their Reactivity and Properties of Polymerization Products

by Andrey Galukhin, Roman Aleshin, Alexander Gerasimov, Alexander Klimovitskii, Roman Nosov, Liana Zubaidullina and Sergey Vyazovkin

Polymers 2025, 17(14), 1909; https://doi.org/10.3390/polym17141909 - 10 Jul 2025

Abstract

Non-isothermal calorimetry is performed to study the kinetics of metal-free A₂/B₂-type azide–alkyne polyaddition between the dipropargyl ether of bisphenol A with different organic diazides. The diazide structure is varied to probe the effect of the nature of a hydrocarbon [...] Read more.

Non-isothermal calorimetry is performed to study the kinetics of metal-free A₂/B₂-type azide–alkyne polyaddition between the dipropargyl ether of bisphenol A with different organic diazides. The diazide structure is varied to probe the effect of the nature of a hydrocarbon spacer between the azide groups on their reactivity. Isoconversional analysis demonstrates that the polymerization processes are characterized by the same activation energy of 84 kJ mol⁻¹ for all studied diazides. It is found that diazides with aromatic spacers demonstrate ~1.6 times higher reactivity than that of diazides with the alkyl spacer. The difference in the reactivity is explained by the difference in the electronic effects of the hydrocarbon spacers on the azide groups as well as by the difference in their steric availability. The veracity of the obtained kinetic parameters is validated by a polymerization test at the time–temperature conditions predicted from the obtained kinetic data followed by independent assessment of the monomer conversion using FTIR. Full article

(This article belongs to the Section Polymer Physics and Theory)

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13 pages, 1305 KiB

Open AccessArticle

A Wavelength Rule for the Analysis of Clusteroluminescence

by Frank B. Peters and Andreas O. Rapp

Polymers 2025, 17(14), 1908; https://doi.org/10.3390/polym17141908 - 10 Jul 2025

Abstract

A key discovery of this study is the strong correlation (r = 0.96) between excitation and emission maxima across chemically distinct clusteroluminogens. All 157 evaluated peaks fall along a single regression line (Ex = 0.844 Em − 12 nm), a pattern that was [...] Read more.

A key discovery of this study is the strong correlation (r = 0.96) between excitation and emission maxima across chemically distinct clusteroluminogens. All 157 evaluated peaks fall along a single regression line (Ex = 0.844 Em − 12 nm), a pattern that was not valid for conventional fluorophores. This suggests a general principle of clusteroluminescence. We show that in lignocellulosic materials, peak positions reflect chemical interactions: isolated lignin and cellulose showed short excitation and emission wavelengths, while native wood exhibited longer wavelengths. Fungal or photoinduced degradation led to a further red-shift. These effects are attributed to increased molecular heterogeneity, reducing the effective energy gap within the lignocellulosic complex. We conclude that the spectral position reflects the degree of molecular interaction rather than the chemical structure of individual molecules. It may serve as a novel analytical parameter for assessing purity and degradation in a wide range of polymers. Full article

(This article belongs to the Special Issue Advanced Preparation and Application of Cellulose: 2nd Edition)

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14 pages, 2757 KiB

Open AccessArticle

Starch Films Reinforced with Pistachio Shell Particles: A Sustainable Biocomposite

by Cynthia G. Flores-Hernandez, Alicia Del Real, María de los Ángeles Cornejo-Villegas, Beatriz Millán-Malo, Gerardo A. Fonseca-Hernández and José Luis Rivera-Armenta

Polymers 2025, 17(14), 1907; https://doi.org/10.3390/polym17141907 - 10 Jul 2025

Abstract

This study investigates the development of corn starch-based biocomposites reinforced with pistachio shell powder, focusing on improving their mechanical and thermal performance. Composite films were prepared by solution casting with pistachio shell contents ranging from 2 wt% to 8 wt% by weight. The [...] Read more.

This study investigates the development of corn starch-based biocomposites reinforced with pistachio shell powder, focusing on improving their mechanical and thermal performance. Composite films were prepared by solution casting with pistachio shell contents ranging from 2 wt% to 8 wt% by weight. The materials were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and tensile testing. The incorporation of pistachio shell particles led to a progressive improvement in tensile strength and elastic modulus, with the highest values observed in the formulation with 8% reinforcement (SP08). The TGA results indicated a shift in degradation temperatures for the sample with the highest percentage, reflecting a higher thermal stability that is attributed to the interactions between the starch, plasticizer, and cellulosic components of the pistachio shell. The FITR spectra shows very similar structures between starch and pistachio. An XRD analysis shows the alpha-type structure for starch and the cellulose type 1 structure for pistachio. Overall, the results suggest that pistachio shell powder can serve as an effective natural reinforcement, improving the functional properties of starch matrices and promoting the development of environmentally friendly materials derived from agro-industrial waste. Full article

(This article belongs to the Special Issue Biobased Polymers and Its Composites)

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Graphical abstract

13 pages, 1612 KiB

Open AccessArticle

Ozone-Mediated Washing Process of Reference Stain Textile Monitors

by Tanja Pušić, Vanja Šantak, Tihana Dekanić and Mirjana Čurlin

Polymers 2025, 17(14), 1906; https://doi.org/10.3390/polym17141906 - 10 Jul 2025

Abstract

The complex chemical composition of certain color stains on textiles requires an optimal proportion of thermal and chemical action in the Sinner cycle of the washing process. In this study, both factors were analyzed by varying the composition of the liquid detergent, bleach, [...] Read more.

The complex chemical composition of certain color stains on textiles requires an optimal proportion of thermal and chemical action in the Sinner cycle of the washing process. In this study, both factors were analyzed by varying the composition of the liquid detergent, bleach, and ozone at temperatures of 30 °C, 40 °C, 60 °C, 75 °C, and 90 °C. Standard cotton fabrics stained with tea, red wine, and blood/milk/ink were selected as monitors, which were evaluated before and after the washing process by spectral parameters. The data sets and their interrelationships were evaluated by a cluster analysis (CA) and ANOVA. An unstained standard cotton fabric was selected as a reference for qualification of the sanitation effect. The stain removal effects showed a selective influence of ozone in the washing processes under the investigated conditions, including the synergy of standard materials—stain monitors and different Sinner cycle factors. The most effective sanitation was achieved in processes using formulations with higher concentrations of liquid detergent (D) and bleaching agents (BA) across all tested temperatures. A lower ozone concentration in combination with lower concentrations of detergents and bleaching agents in washing processes at 30 °C and 40 °C also contributed positively to the effect on sanitation. Full article

(This article belongs to the Special Issue Environmentally Friendly Textiles, Fibers and Their Composites)

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23 pages, 3314 KiB

Open AccessArticle

The Effect of Poly (Methyl Methacrylate) Content on Chemical, Thermomechanical, Mechanical, and Fatigue Life Characteristics of Ternary PC/ABS/PMMA Blends

by Hamdi Kuleyin and Recep Gümrük

Polymers 2025, 17(14), 1905; https://doi.org/10.3390/polym17141905 - 10 Jul 2025

Abstract

Polymer blending techniques enable the tailoring of desired properties for diverse applications. This study investigates the effect of PMMA content on the thermomechanical, chemical, mechanical, and fatigue life properties of PC/ABS/PMMA (polycarbonate/acrylonitrile–butadiene–styrene/polymethylmethacrylate) ternary blends. To this end, various characterization analyses, as well as [...] Read more.

Polymer blending techniques enable the tailoring of desired properties for diverse applications. This study investigates the effect of PMMA content on the thermomechanical, chemical, mechanical, and fatigue life properties of PC/ABS/PMMA (polycarbonate/acrylonitrile–butadiene–styrene/polymethylmethacrylate) ternary blends. To this end, various characterization analyses, as well as tensile, impact, and fatigue tests, were conducted. The results indicate that the viscoelastic modulus improves with increasing PMMA content in ternary blends. Furthermore, PC/ABS/PMMA blends exhibit an immiscible phase morphology. The elastic modulus, yield strength, and tensile strength increase with higher PMMA content, while the elongation at break and impact strength decrease. Fatigue strength and the fatigue strength exponent were found to vary nonlinearly with PMMA content. Compared to PC/ABS blends, PC/ABS/PMMA blends demonstrated improvements of approximately 12% to 58% and 26% to 117% in hysteresis energy and the dynamic elastic modulus, respectively. Additionally, fatigue life cycles improved by 5% to 11% at low stress amplitudes. This experimental study provides comprehensive insight into the complex interplay among the chemical, thermomechanical, mechanical, and fatigue properties of ternary PC/ABS/PMMA blends, highlighting their potential for applications requiring balanced or tailored structural and material characteristics. Full article

(This article belongs to the Section Polymer Analysis and Characterization)

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19 pages, 2134 KiB

Open AccessArticle

Valorization of Rice-Bran and Corn-Flour Hydrolysates for Optimized Polyhydroxybutyrate Biosynthesis: Statistical Process Design and Structural Verification

by Gaurav Shrimali, Hardik Shah, Kashyap Thummar, Esha Rami, Rajeshkumar Chaudhari, Jens Ejbye Schmidt and Ajit Gangawane

Polymers 2025, 17(14), 1904; https://doi.org/10.3390/polym17141904 - 10 Jul 2025

Abstract

The extensive environmental pollution caused by petroleum-based plastics highlights the urgent need for sustainable, economically viable alternatives. The practical challenge of enhancing polyhydroxybutyrate (PHB) production with cost-effective agro-industrial residues—rice-bran and corn-flour hydrolysates—has been demonstrated. Bacillus bingmayongensis GS2 was isolated from soil samples collected [...] Read more.

The extensive environmental pollution caused by petroleum-based plastics highlights the urgent need for sustainable, economically viable alternatives. The practical challenge of enhancing polyhydroxybutyrate (PHB) production with cost-effective agro-industrial residues—rice-bran and corn-flour hydrolysates—has been demonstrated. Bacillus bingmayongensis GS2 was isolated from soil samples collected at the Pirana municipal landfill in Ahmedabad, India, and identified through VITEK-2 biochemical profiling and 16S rDNA sequencing (GenBank accession OQ749793). Initial screening for PHB accumulation was performed using Sudan Black B staining. Optimization via a sequential one-variable-at-a-time (OVAT) approach identified optimal cultivation conditions (36 h inoculum age, 37 °C, pH 7.0, 100 rpm agitation), resulting in a PHB yield of 2.77 g L⁻¹ (66% DCW). Further refinement using a central composite response surface methodology (RSM)—varying rice-bran hydrolysate, corn-flour hydrolysate, peptone concentration, and initial pH—significantly improved the PHB yield to 3.18 g L⁻¹(74% DCW), representing more than a threefold enhancement over unoptimized conditions. Structural validation using Fourier Transform Infrared spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance spectroscopy (¹H-NMR) confirmed the molecular integrity of the produced PHB. That Bacillus bingmayongensis GS2 effectively converts low-cost agro-industrial residues into high-value bioplastics has been demonstrated, indicating substantial industrial potential. Future work will focus on bioreactor scale-up, targeted metabolic-engineering strategies, and comprehensive sustainability evaluations, including life-cycle assessment. Full article

(This article belongs to the Section Biobased and Biodegradable Polymers)

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