Polymers

39 pages, 33532 KB

Open AccessArticle

Multi-Statistical Pragmatic Framework to Study UV Exposure Effects via VIS Reflectance in Automotive Polymer Components

by Jose Amilcar Rizzo-Sierra, Luis Alvaro Montoya-Santiyanes, Cesar Isaza, Karina Anaya, Cristian Felipe Ramirez-Gutierrez and Jonny Paul Zavala de Paz

Polymers 2025, 17(21), 2849; https://doi.org/10.3390/polym17212849 (registering DOI) - 25 Oct 2025

Abstract

This study evaluates the cosmetic degradation of polyethylene (PE) and polypropylene (PP) automotive components under four exposure scenarios—no exposure, outdoor exposure with and without glass shielding, and accelerated UV chamber weathering (ASTM G154)—through the evolution of visible (VIS) reflectance. Thirty-two samples (16 PE, [...] Read more.

This study evaluates the cosmetic degradation of polyethylene (PE) and polypropylene (PP) automotive components under four exposure scenarios—no exposure, outdoor exposure with and without glass shielding, and accelerated UV chamber weathering (ASTM G154)—through the evolution of visible (VIS) reflectance. Thirty-two samples (16 PE, 16 PP) were monitored over five time points; surface reflectance was recorded at 21 wavelengths and summarized into seven VIS bands, and hardness (Shore D) was measured pre/post-exposure. Repeated-measures univariate and multivariate analyses consistently revealed significant effects of Condition, Time, and their interaction on reflectance, with initial-reflectance adjustment improving inference stability across bands. PE exhibited more gradual and coherent reflectance decay, whereas PP showed greater band-to-band variability—most notably under UV chamber exposure. Additionally, hardness decreased in most exposed groups, aligning with optical changes. To place spectral trajectories in a kinetic context, a family of exponential models with small-sample information criterion selection was fitted, yielding

η (t)

—a dimensionless degradation efficiency summarizing spectral change. The contribution of this work is a multi-statistical framework—combining VIS-band-aware summaries with covariate-adjusted univariate/multivariate testing—that supports comparisons across materials and exposure conditions, underscoring the practical value of UV chamber protocols as surrogates for outdoor weathering. In sum, the study demonstrates the effectiveness of multivariate and covariate-adjusted models in quantifying optical degradation of polyolefins, offering pragmatic guidance for assessing mid- to long-term performance in automotive applications. Full article

(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Mexico)

19 pages, 4219 KB

Open AccessArticle

Mitigating Composition Variability in Post-Industrial PC/ABS Recycling via Targeted Compatibilization

by Silvia Zanatta, Eleonora Dal Lago, Filippo Dall’Amico, Carlo Boaretti, Alessandra Lorenzetti, Martina Roso and Michele Modesti

Polymers 2025, 17(21), 2848; https://doi.org/10.3390/polym17212848 (registering DOI) - 25 Oct 2025

Abstract

The growing demand for sustainable solutions in the plastics industry has highlighted the need to reintroduce post-industrial polymer waste into high-performance applications. This study focuses on the mechanical recycling of automotive scraps containing variable proportions of polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS), and a commercial [...] Read more.

The growing demand for sustainable solutions in the plastics industry has highlighted the need to reintroduce post-industrial polymer waste into high-performance applications. This study focuses on the mechanical recycling of automotive scraps containing variable proportions of polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS), and a commercial PC/ABS blend. After determining the composition of two representative batches, a screening of seven commercial compatibilizers and impact modifiers was performed to improve impact strength. Among them, an ethylene–methyl acrylate–glycidyl methacrylate (E-MA-GMA) terpolymer was identified as the most effective additive. Its influence was further investigated through a mixture design approach, varying the composition of the three polymer phases and the additive content (0–10 wt.%). The resulting response surface model revealed a significant increase in impact resistance in PC-rich formulations with increasing E-MA-GMA content, while ABS and PC/ABS showed more complex trends. Rheological, mechanical, and thermal analyses supported the observed behavior, suggesting improved matrix compatibility and reduced degradation during processing. The proposed model enables the prediction of impact performance across a wide range of compositions, offering a practical tool for the optimization of recycled blends. These findings support the potential of targeted compatibilization strategies for closed-loop recycling in the automotive sector. Full article

(This article belongs to the Special Issue Advances in Polymer Recycling and Upcycling: Toward a Circular and Sustainable Future)

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4 pages, 148 KB

Open AccessEditorial

Multifunctional Polymer Composite Materials, 2nd Edition

by Md Najib Alam and Vineet Kumar

Polymers 2025, 17(21), 2847; https://doi.org/10.3390/polym17212847 (registering DOI) - 25 Oct 2025

Abstract

Polymer composite materials have emerged as a key class of advanced materials with robust properties [...] Full article

(This article belongs to the Special Issue Multifunctional Polymer Composite Materials, 2nd Edition)

3 pages, 160 KB

Open AccessEditorial

Recent Highlights in Polymer Analysis and Characterization

by Giulio Malucelli

Polymers 2025, 17(21), 2846; https://doi.org/10.3390/polym17212846 (registering DOI) - 25 Oct 2025

Abstract

Dear colleagues and friends, [...] Full article

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

21 pages, 2915 KB

Open AccessArticle

Poly(ethylene glycol)-graft-Hyaluronic Acid Hydrogels for Angiogenesis

by Miyu Hashimoto, Kazune Oda, Ari Yamamoto, Ik Sung Cho, Yasuhiko Tabata, Masaya Yamamoto and Tooru Ooya

Polymers 2025, 17(21), 2845; https://doi.org/10.3390/polym17212845 (registering DOI) - 24 Oct 2025

Abstract

Hyaluronic acid (HA) hydrogels are promising biomaterials for tissue engineering and drug delivery due to their biocompatibility and biodegradability. The objective of this study was to develop a novel HA-based hydrogel for the controlled release of basic fibroblast growth factor (bFGF) to promote [...] Read more.

Hyaluronic acid (HA) hydrogels are promising biomaterials for tissue engineering and drug delivery due to their biocompatibility and biodegradability. The objective of this study was to develop a novel HA-based hydrogel for the controlled release of basic fibroblast growth factor (bFGF) to promote angiogenesis. A series of PEG-grafted HA hydrogels with varying PEG grafting ratios were synthesized and characterized. We evaluated their physicochemical properties, including swelling ratio, cross-linking density, and enzymatic degradation behavior, and assessed their ability to control bFGF release and induce angiogenesis in a mouse model. The results showed that the PEG-grafting ratio significantly affected the gel properties. Notably, the PEG60-graft-HA hydrogel exhibited a higher swelling ratio and more rapid degradation, suggesting a non-uniform and highly porous structure. In vitro release studies confirmed that while PEG5-graft-HA and PEG15-graft-HA gels showed burst release, the PEG60-graft-HA hydrogel demonstrated sustained release of bFGF over time. Furthermore, in vivo experiments revealed a significant increase in angiogenesis with the PEG60-graft-HA hydrogel, likely due to the prolonged release of active bFGF. These findings suggest that PEG-grafted HA hydrogels, particularly those with a higher PEG grafting ratio, are promising biomaterials for the controlled release of growth factors and applications in tissue regeneration. Full article

(This article belongs to the Special Issue Advanced Hydrogels for Biomedical Application)

26 pages, 2244 KB

Open AccessArticle

Study on Fiber-Fabric Hierarchical Reinforcement for High-Toughness Magnesium Phosphate Cement Composites

by Weipeng Feng, Yuan Fang, Chengman Wang, Peng Cui, Kunde Zhuang, Wenyang Zhang and Zhijun Dong

Polymers 2025, 17(21), 2844; https://doi.org/10.3390/polym17212844 (registering DOI) - 24 Oct 2025

Abstract

Magnesium phosphate cement (MPC) has gained attention in specialized construction applications due to its rapid setting and high early strength, though its inherent brittleness limits structural performance. This study developed an innovative toughening strategy through synergistic reinforcement using hybrid fibers and carbon fiber-reinforced [...] Read more.

Magnesium phosphate cement (MPC) has gained attention in specialized construction applications due to its rapid setting and high early strength, though its inherent brittleness limits structural performance. This study developed an innovative toughening strategy through synergistic reinforcement using hybrid fibers and carbon fiber-reinforced polymer (CFRP) fabric capable of multi-scale crack control. The experimental program systematically evaluated the hybrid fiber system, dosage, and CFRP positioning effects through mechanical testing of 7-day cured specimens. The results indicated that 3.5% fiber dosage optimized flexural–compressive balance (45% flexural gain with <20% compressive reduction), while CFRP integration at 19 mm displacement enhanced flexural capacity via multi-scale reinforcement. Fracture analysis revealed that the combined system increases post-cracking strength by 60% through coordinated crack bridging at micro (fiber) and macro (CFRP) scales. These findings elucidated the mechanisms by which fiber–CFRP interaction mitigates MPC’s brittleness through hierarchical crack control while maintaining its rapid hardening advantages. The study established quantitative design guidelines, showing the fiber composition of CF/WSF/CPS15 = 1/1/1 with 19 mm CFRP placement achieves optimal toughness–flexural balance (f_f/f_c > 0.38). The developed composite system reduced brittleness through effective crack suppression across scales, confirming its capability to transform fracture behavior from brittle to quasi-ductile. This work advances MPC’s engineering applicability by resolving its mechanical limitations through rationally designed composite systems, with particular relevance to rapid repair scenarios requiring both early strength and damage tolerance, expanding its potential in specialized construction where conventional cement proves inadequate. Full article

(This article belongs to the Section Polymer Fibers)

29 pages, 4966 KB

Open AccessArticle

Structure–Property Relationships in Epoxy–Anhydride Systems: A Comprehensive Comparative Study of Cycloaliphatic, Novolac, and Aromatic Prepolymers

by Stephane Patry, Alban Asseray, Mickaël Berne, Valéry Loriot, Luc Loriot and Jean-Pierre Habas

Polymers 2025, 17(21), 2843; https://doi.org/10.3390/polym17212843 (registering DOI) - 24 Oct 2025

Abstract

This study provides a comprehensive quantitative comparison of three structurally distinct epoxy prepolymers—cycloaliphatic, novolac, and bis-aromatic (BADGE)—cured with a single hardener, methyl nadic anhydride (MNA), and catalyzed by 1-methylimidazole under strictly identical stoichiometric and thermal conditions. Each formulation was optimized in terms of [...] Read more.

This study provides a comprehensive quantitative comparison of three structurally distinct epoxy prepolymers—cycloaliphatic, novolac, and bis-aromatic (BADGE)—cured with a single hardener, methyl nadic anhydride (MNA), and catalyzed by 1-methylimidazole under strictly identical stoichiometric and thermal conditions. Each formulation was optimized in terms of epoxy/anhydride ratio and catalyst concentration to ensure meaningful cross-comparison under representative cure conditions. A multi-technique approach combining differential scanning calorimetry (DSC), dynamic rheometry, and thermogravimetric analysis (TGA) was employed to jointly assess cure kinetics, network build-up, and long-term thermal stability. DSC analyses provided reaction enthalpies and glass transition temperatures (Tg) ranging from 145 °C (BADGE-MNA) to 253 °C (cycloaliphatic ECy-MNA) after stabilization of the curing reaction under the chosen thermal protocol, enabling experimental fine-tuning of stoichiometry beyond the theoretical 1:1 ratio. Isothermal rheology revealed gel times of approximately 14 s for novolac, 16 s for BADGE, and 20 s for the cycloaliphatic system at 200 °C, defining a clear hierarchy of reactivity (Novolac > BADGE > ECy). Post-cure thermomechanical performance and thermal aging resistance (100 h at 250 °C) were assessed via rheometry and TGA under both dynamic and isothermal conditions. They demonstrated that the novolac-based resin retained approximately 93.7% of its initial mass, confirming its outstanding thermo-oxidative stability. The three systems exhibited distinct trade-offs between reactivity and thermal resistance: the novolac resin showed superior thermal endurance but, owing to its highly aromatic and rigid structure, limited flowability, while the cycloaliphatic resin exhibited greater molecular mobility and longer pot life but reduced stability. Overall, this work provides a comprehensive and quantitatively consistent benchmark, consolidating stoichiometric control, DSC and rheological reactivity, Tg evolution, thermomechanical stability, and degradation behavior within a single unified experimental framework. The results offer reliable reference data for modeling, formulation, and possible use of epoxy–anhydride thermosets at temperatures above 200 °C. Full article

(This article belongs to the Special Issue Epoxy Resins and Epoxy-Based Composites: Research and Development)

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18 pages, 6942 KB

Open AccessArticle

Micellization Studies of Block Copolymers of Poly(N-vinyl Pyrrolidone) and n-Alkyl-Substituted Poly(Vinyl Esters) in Tetrahydrofuran

by Nikoletta Roka, Vasileios-Christos Skiadas, Areti Kolovou, Theodosia-Panagiota Papazoglou and Marinos Pitsikalis

Polymers 2025, 17(21), 2842; https://doi.org/10.3390/polym17212842 (registering DOI) - 24 Oct 2025

Abstract

The association behavior of amphiphilic block copolymers of N-vinyl pyrrolidone (NVP) and several vinyl esters (Ves) (PNVP-b-PVEs), as exemplified by vinyl butyrate (VBu), vinyl decanoate (VDc), and vinyl stearate (VSt), was studied in tetrahydrofuran (THF), which serves as the selective solvent for the [...] Read more.

The association behavior of amphiphilic block copolymers of N-vinyl pyrrolidone (NVP) and several vinyl esters (Ves) (PNVP-b-PVEs), as exemplified by vinyl butyrate (VBu), vinyl decanoate (VDc), and vinyl stearate (VSt), was studied in tetrahydrofuran (THF), which serves as the selective solvent for the PVE blocks. Static (SLS) and dynamic light scattering (DLS) techniques were adopted as the tools to investigate micellar properties and acquire information regarding the degree of association, the hydrodynamic radii, and the shape of the aggregates. In addition, CONTIN analysis provided insights concerning the association equilibria in THF solutions. The effect of the chemical structure of the corona-forming PVE block on the association process was investigated. Finally, the experimental results were compared with those obtained in previous studies describing the micellization properties of block copolymers consisting of PNVP and polymethacrylate blocks in the same selective solvent. Full article

(This article belongs to the Section Polymer Chemistry)

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22 pages, 1633 KB

Open AccessArticle

Effect of the Crosslinker Introduction Stage on the Structure and Properties of Xanthan Gum–Acrylamide Graft Copolymer

by Anton K. Smirnov, Diana F. Pelipenko, Sergei L. Shmakov, Andrey M. Zakharevich and Anna B. Shipovskaya

Polymers 2025, 17(21), 2841; https://doi.org/10.3390/polym17212841 (registering DOI) - 24 Oct 2025

Abstract

Graft copolymers of polysaccharides with side chains of carbon-chain monomers have significant potential for a variety of practical applications. In this work, the effect of the N,N-methylenebisacrylamide (MBA) introduction stage and acrylamide concentration in microwave-assisted radical copolymerization with [...] Read more.

Graft copolymers of polysaccharides with side chains of carbon-chain monomers have significant potential for a variety of practical applications. In this work, the effect of the N,N-methylenebisacrylamide (MBA) introduction stage and acrylamide concentration in microwave-assisted radical copolymerization with xanthan gum on the structure and sorption properties of the cross-linked graft copolymer was studied. It has been found that the spatial network density and average molecular weight of interstitial fragments can be controlled by varying these factors. Moderate crystallinity (<50%) and a highly developed surface of our synthesized samples were revealed using XRD and SEM. The graft copolymer exhibits the Schroeder effect; its liquid water sorption obeys Fick’s law and increases with MBA introduction at later stages and with increasing grafting degree, reaching 17.2 g/g. Studying the methylene blue sorption kinetics using pseudo-first/pseudo-second order models, a combined model and an average pseudo-order model have shown that the lower the monomer concentration in the reaction mixture and the earlier (from the onset of the reaction) the cross-linking agent is introduced, the higher the equilibrium sorption. The observed “equilibrium degree of sorption on xanthan gum vs. pseudo-order” relationship, which passes through a minimum, is explained by chemisorption and the sorbate consumption effect. An assumption is made about the prospects of using our synthesized copolymers for designing selective sorbents and ion-exchange membranes. Full article

(This article belongs to the Section Polymer Chemistry)

16 pages, 4691 KB

Open AccessArticle

Evaluation of Workability and Crack Resistance of Recycled Plastic Asphalt Mixtures

by Haosen Jing, Riccardo Monticelli, Claudia Graiff, Laura Bergamonti, Elena Romeo and Gabriele Tebaldi

Polymers 2025, 17(21), 2840; https://doi.org/10.3390/polym17212840 (registering DOI) - 24 Oct 2025

Abstract

To address the global plastic crisis, recycled plastics from food packaging were used as road materials by the dry method for practical application research. First, the main components of the recycled plastics were identified based on FTIR, and their thermal stability was evaluated [...] Read more.

To address the global plastic crisis, recycled plastics from food packaging were used as road materials by the dry method for practical application research. First, the main components of the recycled plastics were identified based on FTIR, and their thermal stability was evaluated through DSC, TG, and microscopic analysis. Then, the workability of the plastic–asphalt mixture was evaluated using the gyratory compaction indicator, void content, and compaction energy index (CEI). Finally, the effect of reused plastics on the cracking resistance of bituminous mixtures was examined with the Superpave IDT test. The results indicate that recycled plastics from food packaging are polyolefin composite materials, primarily consisting of Low-Density Polyethylene (LDPE), Linear Low-Density Polyethylene (LLDPE), High-Density Polyethylene (HDPE), and Polypropylene (PP), and that their thermal stability meets production requirements. Good compaction performance was observed with plastic content below 2% of the aggregate weight, while higher contents reduced void content due to the space occupied by plastics. When the plastic content increased from 0.5% to 2.0%, creep compliance decreased from 68.4% to 77.87%, while the m-value, tensile strength, and elastic energy maximum decreased by 30.77%, 5.6%, and 7%, respectively. In contrast, the failure strain, fracture energy, and maximum DSCE increased by 25.86%, 87.43%, and 133.05%, respectively. The recycled plastic enhanced the toughness of the asphalt mixture, increasing the dissipated energy during crack propagation and improving its resistance to permanent deformation. Moreover, the plastics hindered crack propagation through a bridging effect, leading to fewer cracks within plastic zones compared with surrounding areas. This study provides actionable guidance for the application of composite plastics in asphalt pavements and supports their sustainable development. Full article

(This article belongs to the Section Circular and Green Sustainable Polymer Science)

14 pages, 5797 KB

Open AccessArticle

Investigation of Blade Printing Technique for Nano-Structuring Piezoelectric Polymer Ink in a Porous Anodic Aluminum Oxide

by Tsvetozar Tsanev and Mariya Aleksandrova

Polymers 2025, 17(21), 2839; https://doi.org/10.3390/polym17212839 (registering DOI) - 24 Oct 2025

Abstract

In this work, we investigated the use of a piezoelectric flexible device for energy harvesting. The main goal of the study was to fill the nanostructured pores of anodic aluminum oxide (AAO) films with piezoelectric polymer (PVDF-TrFE) via a modified conventional screen printing [...] Read more.

In this work, we investigated the use of a piezoelectric flexible device for energy harvesting. The main goal of the study was to fill the nanostructured pores of anodic aluminum oxide (AAO) films with piezoelectric polymer (PVDF-TrFE) via a modified conventional screen printing technique using blade printing. In this way, it is possible to obtain a composite from nanostructured thin films of polymer nanorods that shows improved charge generation ability compared to other non-nanostructured composites or pure (non-composite) aluminum with similar dimensions. This behavior is due to the effect of the highly developed surface of the material used to fill in the AAO nanopore template and its ability to withstand the application of higher mechanical loads to the structured piezoelectric material during deformation. The contact blade print filling technique can produce nanostructured piezoelectric polymer films with precise geometric parameters in terms of thickness and nanorod diameters, at around 200 nm, and a length of 12 μm. At a low frequency of 17 Hz, the highest root-mean-square (RMS) voltage generated using the nanostructured AAO/PVDF-TrFE sample with aluminum electrodes was around 395 mV. At high frequencies above 1700 Hz, the highest RMS voltage generated using the nanostructured AAO/PVDF-TrFE sample with gold electrodes was around 680 mV. The RMS voltage generated using a uniform (non-nanostructured) layer of PVDF-TrFE was 15% lower across the whole frequency range. Full article

(This article belongs to the Special Issue Advanced Polymers for Harnessing Power and Energy)

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32 pages, 1560 KB

Open AccessReview

Chitosan (Nano)formulations as Therapeutic Tools for Neurodegenerative Diseases: A Comprehensive Review

by Adriana C. C. Gomes, Adelaide Almeida, Carmen S. R. Freire and Bárbara Leite Ferreira

Polymers 2025, 17(21), 2838; https://doi.org/10.3390/polym17212838 (registering DOI) - 24 Oct 2025

Abstract

According to the World Health Organization, Alzheimer’s disease and other forms of dementia were the seventh leading cause of death in 2021. The prevalence of these disorders is predictable to increase with life expectancy, and their control is hampered by several factors, including [...] Read more.

According to the World Health Organization, Alzheimer’s disease and other forms of dementia were the seventh leading cause of death in 2021. The prevalence of these disorders is predictable to increase with life expectancy, and their control is hampered by several factors, including late diagnosis due to the lack of specific biomarkers and the absence of disease-modifying treatments, as currently available therapies can only lighten some of the symptoms. Nanotechnology could be the key to overcoming some of the limitations associated with neurodegenerative diseases, as nanomaterials have excellent properties compared to their bulk counterparts and can be used as drug delivery systems, diagnostic tools and platforms for tissue regeneration. Chitosan is a biopolymer with numerous properties that impart it with great potential for biomedical applications, in particular its ability to cross the blood–brain barrier and its versatility in nanoscale design. In this context, the aim of this review is to provide an in-depth analysis of the latest developments and future opportunities for chitosan (nano)formulations for the treatment and management of neurodegenerative diseases. Full article

(This article belongs to the Special Issue New Advances in Bio-Based Polymers)

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17 pages, 2281 KB

Open AccessArticle

Nanomedicines for Delivery of Cytarabine: Effect of Carrier Structure and Spacer on the Anti-Lymphoma Efficacy

by Robert Pola, Eliška Grosmanová, Michal Pechar, Libor Kostka, Eva Pokorná, Liliana Tušková, Pavel Klener and Tomáš Etrych

Polymers 2025, 17(21), 2837; https://doi.org/10.3390/polym17212837 (registering DOI) - 24 Oct 2025

Abstract

High-dose therapy with cytarabine (araC) is a standard treatment for aggressive non-Hodgkin lymphomas, but its efficacy is limited by rapid enzymatic degradation. To overcome this, araC was conjugated to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers to form linear and star-like nanomedicines using six different spacers: [...] Read more.

High-dose therapy with cytarabine (araC) is a standard treatment for aggressive non-Hodgkin lymphomas, but its efficacy is limited by rapid enzymatic degradation. To overcome this, araC was conjugated to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers to form linear and star-like nanomedicines using six different spacers: 3-aminopropanoyl, 5-pentanoyl, 6-aminohexanoyl, 4-aminobenzoyl, glycyl, and diglycyl. The conjugates contained 12.5–14.7 wt% araC and exhibited distinct hydrolytic release profiles at pH 7.4. LC1 (3-aminopropanoyl) and LC6 (diglycyl) released the drug most rapidly (~80% bound after 72 h), and LC2, LC3, and the star conjugate SC1 showed intermediate stability (~90%), while LC4 (4-aminobenzoyl) was most stable (~95%). In vivo, all conjugates markedly suppressed tumor growth in patient-derived xenograft models of mantle cell and Burkitt lymphoma compared with free araC. LC1 and LC2 provided the most durable tumor control, delaying regrowth beyond 40 days, and SC1 achieved comparable efficacy at a reduced araC-equivalent dose (2 mg/mouse vs. 3 mg/mouse for linear conjugates). These results demonstrate that spacer structure critically influences drug release and identify LC1 and LC2 as promising candidates for further development in lymphoma therapy. Full article

(This article belongs to the Section Polymer Applications)

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28 pages, 3481 KB

Open AccessArticle

Development and Characterization of Scented PLA-Based Biocomposites Reinforced with Spent Coffee Grounds and Lignin for FDM 3D Printing

by Zeineb Siala, Ahmed Koubaa, Sofiane Guessasma, Nicolas Stephant, Ahmed Elloumi and Martin Beauregard

Polymers 2025, 17(21), 2836; https://doi.org/10.3390/polym17212836 (registering DOI) - 24 Oct 2025

Abstract

This study investigates the development of biodegradable, scented bio-composite filaments incorporating industrial residues, specifically spent coffee grounds (SCG) and lignin (LI), into a PLA matrix for FDM 3D printing. Two fragrance additives, essential oil (EO) and microencapsulated fragrance powder (FP), were introduced (3%) [...] Read more.

This study investigates the development of biodegradable, scented bio-composite filaments incorporating industrial residues, specifically spent coffee grounds (SCG) and lignin (LI), into a PLA matrix for FDM 3D printing. Two fragrance additives, essential oil (EO) and microencapsulated fragrance powder (FP), were introduced (3%) to enhance sensory properties. The research investigates the effects of filler content (5%, 10%, and 15%) and fragrance additives on the surface chemistry (FTIR), thermal stability (TGA and DSC), mechanical properties (Tensile, flexural and impact), microstructure, and dimensional stability (Water absorption test and thickness swelling). Incorporating industrial residues and additives into PLA reduced the thermal stability, the degradation temperature and the glass transition temperature but increased the residual mass and the crystallinity. The effect of lignin was more pronounced than that of SCG, significantly influencing these thermal properties. Increasing the filler content of spent coffee grounds and lignin also led to a progressive decrease in tensile, flexural, and impact strength due to poor interfacial adhesion and increased void formation. However, lignin-based biocomposites exhibited enhanced stiffness at lower concentrations (≤10%), while biocomposites containing 15% SCG doubled their elongation at break compared to pure PLA. Adding fragrance reduced the mechanical strength but improved ductility due to plasticizer-like interactions. Microstructural analysis revealed heterogeneity in the biocomposites’ fracture surface characterized by the presence of pores, filler agglomeration, and delamination, indicating uneven filler dispersion and limited interfacial adhesion, particularly at high filler concentrations. The water absorption and dimensional stability of 3D-printed biocomposites increased progressively with the addition of residues. The presence of essential oil slightly improved water resistance by forming hydrogen bonds that limited moisture absorption. This article adds significant value by extending the potential applications of biocomposites beyond conventional engineering uses, making them particularly suitable for the fashion and design sectors, where multi-sensory and sustainable materials are increasingly sought after. Full article

(This article belongs to the Special Issue Mechanical and Dynamic Characterization of Polymeric Composites, 3rd Edition)

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32 pages, 6328 KB

Open AccessArticle

A Combined Experimental, Theoretical, and Simulation Approach to the Effects of GNPs and MWCNTs on Joule Heating Behavior of 3D Printed PVDF Nanocomposites

by Giovanni Spinelli, Rosella Guarini, Rumiana Kotsilkova, Evgeni Ivanov and Vladimir Georgiev

Polymers 2025, 17(21), 2835; https://doi.org/10.3390/polym17212835 (registering DOI) - 24 Oct 2025

Abstract

The thermal behavior of 3D-printed polyvinylidene fluoride (PVDF)-based composites enhanced with carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and their hybrid formulations was investigated under Joule heating at applied voltages of 2, 3, and 4 V. The influence of filler type and weight fraction [...] Read more.

The thermal behavior of 3D-printed polyvinylidene fluoride (PVDF)-based composites enhanced with carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and their hybrid formulations was investigated under Joule heating at applied voltages of 2, 3, and 4 V. The influence of filler type and weight fraction on both electrical and thermal conductivity was systematically assessed using a Design of Experiments (DoE) approach. Response Surface Methodology (RSM) was employed to derive an analytical relationship linking conductivity values to filler loading, revealing clear trends and interaction effects. Among all tested formulations, the composite containing 6 wt% of GNPs exhibited the highest performance in terms of thermal response and electrical conductivity, reaching a steady-state temperature of 88.1 °C under an applied voltage of just 4 V. This optimal formulation was further analyzed through multiphysics simulations, validated against experimental data and theoretical predictions, to evaluate its effectiveness for potential practical applications—particularly in de-icing systems leveraging Joule heating. The integrated experimental–theoretical–numerical workflow proposed herein offers a robust strategy for guiding the development and optimization of next-generation polymer nanocomposites for thermal management technologies. Full article

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

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17 pages, 1172 KB

Open AccessArticle

UV LED Curing for Silicone Hydrogel Contact Lenses: Breakthrough in Curing Properties and Cosmetic Characteristics

by Saravanan Nanda Kumar, Nadia Adrus, Jamarosliza Jamaluddin, Farahin M. Mizi, Fatria Syaimima Saiful Azim and James Jeyadeva Govindasamy

Polymers 2025, 17(21), 2834; https://doi.org/10.3390/polym17212834 - 24 Oct 2025

Abstract

Ultraviolet light-emitting diode (UV LED) technology offers advantages over conventional UV mercury (UV Hg) lamps, including precise wavelength control, high energy efficiency and rapid curing. While UV LED is widely applied in sectors like dentistry, printing, and electronics, its application in contact lens [...] Read more.

Ultraviolet light-emitting diode (UV LED) technology offers advantages over conventional UV mercury (UV Hg) lamps, including precise wavelength control, high energy efficiency and rapid curing. While UV LED is widely applied in sectors like dentistry, printing, and electronics, its application in contact lens manufacturing remains relatively low. This study evaluates the feasibility of integrating UV LED technology curing as a replacement for UV Hg lamps to produce silicone hydrogel contact lenses. Many manufacturers utilizing UV Hg systems encounter challenges such as extended curing times and increased cosmetic defect rates. In this study, lenses were formulated using a mixture of hydrophobic macro-monomer, silicone monomer, and hydrophilic monomer. The formulations were cured using both UV LED and UV Hg lamps systems under controlled intensities, and two curing configurations were assessed: single-sided (SC) and double-sided (DC). The UV Hg light intensity was maintained between 1.1 and 3.1 mW/cm², reflecting standard production values, while the UV LED intensity was set at 32 mW/cm² to ensure uniform light distribution in the mold. The findings showed an improved degree of conversion (DOC) for UV LED cured lenses (86–88%) compared to UV Hg (79.5–82.3%), along with increased water content (ranging between 34 and 36.8%) and ion permeability (7.1–8.3 mm²/min). The optical properties of the cured lenses remained consistent across both methods. Notably, UV LED curing reduced cosmetic defects by up to 50% and shortened curing time by 3 to 4 times. These enhancements support UV LED as a superior alternative for contact lens curing, enabling scalable, efficient, and high-quality manufacturing. Full article

(This article belongs to the Special Issue New Insights into Photopolymerization)

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17 pages, 6471 KB

Open AccessArticle

Bio-Adhesive Lignin-Reinforced Epoxy Acrylate (EA)-Based Composite as a DLP 3D Printing Material

by Jeonghong Ha and Jong Wan Ko

Polymers 2025, 17(21), 2833; https://doi.org/10.3390/polym17212833 - 23 Oct 2025

Abstract

Digital light processing (DLP) 3D printing is a powerful additive manufacturing technique but is limited by the relatively low mechanical strength of cured neat resin parts. In this study, a renewable bio-adhesive lignin was introduced as a reinforcing filler into a bisphenol A-type [...] Read more.

Digital light processing (DLP) 3D printing is a powerful additive manufacturing technique but is limited by the relatively low mechanical strength of cured neat resin parts. In this study, a renewable bio-adhesive lignin was introduced as a reinforcing filler into a bisphenol A-type epoxy acrylate (EA) photocurable resin to enhance the mechanical performance of DLP-printed components. Lignin was incorporated at low concentrations (0–0.5 wt%), and three dispersion methods—magnetic stirring, planetary mixing, and ultrasonication—were compared to optimize the filler distribution. Cure depth tests and optical microscopy confirmed that ultrasonication (40 kHz, 5 h) achieved the most homogeneous dispersion, yielding a cure depth nearly matching that of the neat resin. DLP printing of tensile specimens demonstrated that as little as 0.025 wt% lignin increased tensile strength by ~39% (from 44.9 MPa to 62.2 MPa) compared to the neat resin, while maintaining similar elongation at break. Surface hardness also improved by over 40% at this optimal lignin content. However, higher lignin loadings (≥0.05 wt%) led to particle agglomeration, resulting in diminished mechanical gains and impaired printability (e.g., distortion and incomplete curing at 1 wt%). Fractographic analysis of broken specimens revealed that well-dispersed lignin particles act to deflect and hinder crack propagation, thereby enhancing fracture resistance. Overall, this work demonstrates a simple and sustainable approach to reinforce DLP 3D-printed polymers using biopolymer lignin, achieving significant improvements in mechanical properties while highlighting the value of bio-derived additives for advanced photopolymer 3D printing applications. Full article

(This article belongs to the Special Issue Multiscale and Multi-Physical Behavior of Polymers and Polymer Composites)

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3 pages, 144 KB

Open AccessEditorial

The Polymer Physics and Theory Section

by Martin Kröger

Polymers 2025, 17(21), 2832; https://doi.org/10.3390/polym17212832 - 23 Oct 2025

Abstract

The section “Polymer Physics and Theory” of Polymers has significantly grown in quality since 2023 [...] Full article

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

25 pages, 7761 KB

Open AccessArticle

A Study on Thin Cooling Layers Between the Cooling Channel and Cavity in the Injection Molding Process for Mold Temperature Control to Enhance Weld Line Flexural Strength in Plastic Products

by Tran-Phu Nguyen, Pham Thi Mai Khanh, Pham Son Minh, Tran Minh The Uyen and Bui Chan Thanh

Polymers 2025, 17(21), 2831; https://doi.org/10.3390/polym17212831 - 23 Oct 2025

Abstract

Weld lines in injection-molded plastics often act as structural weak points that reduce mechanical performance. Enhancing weld line strength is therefore essential to improve product reliability and service life. This study aims to develop and validate an injection mold system capable of localized [...] Read more.

Weld lines in injection-molded plastics often act as structural weak points that reduce mechanical performance. Enhancing weld line strength is therefore essential to improve product reliability and service life. This study aims to develop and validate an injection mold system capable of localized cavity temperature control to strengthen weld line regions. A specialized mold with an integrated cooling layer was designed to enable rapid thermal response during molding. The Taguchi method was applied to optimize three key parameters—part thickness, melt temperature, and injection pressure—to maximize weld line flexural strength. Experiments based on an L25 orthogonal array revealed that weld line stress varied significantly across parameter combinations, with a maximum of 109.23 MPa. A subsequent validation test conducted under the optimal conditions (250 °C melt temperature, 1.5 mm part thickness, and 16 MPa injection pressure) achieved an enhanced weld line stress of 121.88 MPa, confirming the reliability of the Taguchi-based optimization. Among the factors studied, part thickness had the greatest influence, followed by injection pressure, while melt temperature had the smallest effect. These results demonstrate that combining cavity temperature control with systematic parameter optimization provides an effective strategy to enhance weld line strength in high-performance plastic components. Full article

(This article belongs to the Section Polymer Processing and Engineering)

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20 pages, 3368 KB

Open AccessArticle

Assessing Lemon Peel Waste as a Solid Biofuel: A Study of Its Combustion Behaviour, Kinetics, and Thermodynamics

by Mohamed Anwar Ismail, Ibrahim Dubdub, Suleiman Mousa, Mohammed Al-Yaari, Majdi Ameen Alfaiad and Abdullah Alshehab

Polymers 2025, 17(21), 2830; https://doi.org/10.3390/polym17212830 - 23 Oct 2025

Abstract

This study provides a comprehensive analysis of lemon peel (LP) combustion behaviour using combined physicochemical characterization and non-isothermal thermogravimetric kinetics. To achieve this, LP was characterized for its proximate and ultimate composition, with its structure analysed via FTIR, XRD, and SEM. Thermogravimetric analysis [...] Read more.

This study provides a comprehensive analysis of lemon peel (LP) combustion behaviour using combined physicochemical characterization and non-isothermal thermogravimetric kinetics. To achieve this, LP was characterized for its proximate and ultimate composition, with its structure analysed via FTIR, XRD, and SEM. Thermogravimetric analysis (TGA) was then performed at high heating rates (20–80 K min⁻¹) to investigate combustion stages, and kinetic and thermodynamic parameters were determined using six model-free and one model-fitting method. The results revealed a high heating value (23.02 MJ kg⁻¹) and high volatile matter (73.2 wt%), establishing LP’s significant energy potential. TGA displayed four distinct decomposition stages corresponding to dehydration, pectin/hemicellulose, cellulose, and lignin/char combustion. Kinetic analysis yielded activation energies that varied with conversion, peaking at approximately 304 kJ mol⁻¹, and a three-dimensional diffusion (D3) mechanism was identified as the rate-limiting step. In conclusion, while its high energy content and low nitrogen (1.26 wt%) and sulphur (0.20 wt%) content make LP an attractive low-emission biofuel, its viability is challenged by a high potassium concentration in the ash (34.8 wt% K₂O), posing a severe risk of slagging. This study provides the comprehensive combustion kinetic data for LP at high heating rates, which is essential for designing appropriate energy conversion technologies and ash management strategies. Full article

(This article belongs to the Special Issue Advances in Cellulose and Wood-Based Composites)

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20 pages, 2651 KB

Open AccessArticle

Evaluation of Rheological Properties of Warm Mix Flame-Retardant Asphalt (WMFRA) Binder Suitable for Tunnel Area

by Bo Zhang, Juan Liu, Qiaoli Le and Zhen Lu

Polymers 2025, 17(21), 2829; https://doi.org/10.3390/polym17212829 - 23 Oct 2025

Abstract

This study aimed to systematically evaluate the rheological properties of warm mix flame-retardant asphalt (WMFRA). First, conventional performance tests were conducted on the prepared warm mix rubberized asphalt (WMRA), incorporating different warm mix agents in order to screen out an agent with optimum [...] Read more.

This study aimed to systematically evaluate the rheological properties of warm mix flame-retardant asphalt (WMFRA). First, conventional performance tests were conducted on the prepared warm mix rubberized asphalt (WMRA), incorporating different warm mix agents in order to screen out an agent with optimum performance. Subsequently, limestone power (LP), aluminum trihydrate (ATH), OA composed of ATH and organically modified montmorillonite (OMMT), and zinc borate (ZK) were employed in the oxygen index (OI) test of WMFRA to determine the optimal dosage of flame retardants. Finally, a dynamic shear rheometer (DSR) and a bending beam rheometer (BBR) were used to evaluate the rheological properties of WMFRA. The results showed that the R-Type warm mix agent was superior to S-Type in reducing consistency and improving low-temperature cracking resistance but slightly weakened high-temperature stability. The OA composite flame retardant could enhance the OI from 20.16% to 24% at 15wt% dosage, thereby meeting the specified flame-retardant requirement. Furthermore, OA could markedly boost the high-temperature performance of WMFRA, exhibiting significantly higher complex modulus (G*) and rutting factor (G*/sinδ) compared to WMFRA with other flame retardants. In general, all flame retardants reduced the temperature sensitivity of WMFRA, with ZK being the most effective at 12.6%. Regarding low-temperature performance, LP and ATH improved stress relaxation of WMFRA, while ZK and OA impaired this capability. All flame retardants reduced low-temperature flexibility, but the low-temperature behavior was still dominated by the S(t). For fatigue performance, LP and ATH degraded the fatigue performance by advancing the damage time by 958.9 s and 669.7 s, respectively. In contrast, ZK improved fatigue performance by increasing the complex shear modulus, thereby extending the fatigue life (N_f50) by 3.2%. This study provided a theoretical basis for the formulation optimization of WMFRA. Full article

(This article belongs to the Special Issue Sustainable Polymer Materials for Pavement Applications)

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49 pages, 9683 KB

Open AccessReview

Towards Fire-Safe Polymer Electrolytes for Lithium-Ion Batteries: Strategies for Electrolyte Design and Structural Design

by Khang Le Truong and Joonho Bae

Polymers 2025, 17(21), 2828; https://doi.org/10.3390/polym17212828 (registering DOI) - 23 Oct 2025

Abstract

Lithium-ion batteries, widely used in phones and electric vehicles, pose safety concerns due to the flammability of conventional liquid electrolytes, which are prone to ignition under elevated temperatures and mechanical stress, increasing the risk of fire. Polymer electrolytes have been employed as a [...] Read more.

Lithium-ion batteries, widely used in phones and electric vehicles, pose safety concerns due to the flammability of conventional liquid electrolytes, which are prone to ignition under elevated temperatures and mechanical stress, increasing the risk of fire. Polymer electrolytes have been employed as a safer solution thanks to their superior thermal stability and mechanical strength. However, despite these advantages, many polymer matrices pose a fire hazard, limiting their potential. This review assesses recent advances in enhancing the flame retardancy of polymer electrolytes through a variety of strategies, namely the incorporation of flame-retardant additives, the addition of nanoscale fillers to improve thermal resistance, and the design of layered or hybrid polymer membrane structures that function as thermal barriers. This review evaluates the effectiveness of these methods, examining their flame-retardancy as well as their influences on ionic conductivity and overall battery performance. By highlighting recent progress and enduring safety challenges in solid-state batteries, it aims to offer insights for developing lithium batteries with enhanced safety and high performance. Full article

(This article belongs to the Special Issue Polymeric Materials for Next-Generation Energy Storage)

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23 pages, 3685 KB

Open AccessArticle

Ballistic Performance of Raffia Fabric-Reinforced Epoxy Composites as an Intermediate Layer in Multilayered Armor Systems

by Douglas Santos Silva, Raí Felipe Pereira Junio, Leticia dos Santos Aguilera, Sergio Neves Monteiro and Marcelo Henrique Prado da Silva

Polymers 2025, 17(21), 2827; https://doi.org/10.3390/polym17212827 - 23 Oct 2025

Abstract

This study investigates the ballistic performance of epoxy matrix composites reinforced with raffia fabric, aiming to evaluate their potential as the second layer in multilayered armor systems (MAS), replacing conventional synthetic aramid (Kevlar™) laminates. Composite plates with different volumetric fractions of raffia fabric [...] Read more.

This study investigates the ballistic performance of epoxy matrix composites reinforced with raffia fabric, aiming to evaluate their potential as the second layer in multilayered armor systems (MAS), replacing conventional synthetic aramid (Kevlar™) laminates. Composite plates with different volumetric fractions of raffia fabric (10, 20, and 30%) were manufactured and integrated with a ceramic front layer (Al₂O₃/Nb₂O₅) in MAS structures, which were then subjected to ballistic impact tests using high-energy 7.62 mm caliber ammunition. The backface signature (indentation depth) measured in ballistic clay, used as a human body simulant, showed that only the 10% raffia-reinforced composite (ER10) met the National Institute of Justice (NIJ 0101.06) safety threshold of 44 mm. Higher raffia contents (20% and 30%) led to increased indentation, compromising ballistic integrity. Scanning electron microscopy (SEM) of the fractured surfaces revealed typical energy dissipation mechanisms, such as fiber rupture, fiber pull-out, and interfacial delamination. The results indicate that raffia fabric composites with 10% fiber content can serve as a cost-effective and sustainable alternative to Kevlar™ in personal armor applications, while maintaining compliance with ballistic protection standards. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)

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14 pages, 2186 KB

Open AccessArticle

Biosensor Based on Electrochemical Analysis for Staphylococcus aureus Detection with Molecular Imprinted Polymer Technique

by Naphatsawan Vongmanee, Jindapa Nampeng, Chuchart Pintavirooj and Sarinporn Visitsattapongse

Polymers 2025, 17(21), 2826; https://doi.org/10.3390/polym17212826 - 23 Oct 2025

Abstract

Staphylococcus aureus (S. aureus) is one of the most common hospital-acquired pathogens and poses a serious threat to patients with weakened immune systems. Transmission can occur through foodborne illness, skin infections, abscess formation, and bloodstream invasion. The most severe complication arises [...] Read more.

Staphylococcus aureus (S. aureus) is one of the most common hospital-acquired pathogens and poses a serious threat to patients with weakened immune systems. Transmission can occur through foodborne illness, skin infections, abscess formation, and bloodstream invasion. The most severe complication arises when S. aureus infects the heart, leading to valve damage and potentially progressing to heart failure. In addition, many strains have developed strong resistance to conventional antibiotic therapies, making treatment increasingly difficult. These challenges highlight the importance of early detection for effective prevention and management. This research focuses on the development of a polymer composite incorporating hydroxyproline for the preparation of molecularly imprinted polymers (MIPs) designed for the rapid detection of S. aureus. The sensing platform, based on electrochemical principles, enabled sensitive and efficient analysis of bacterial samples. The sensor exhibited a broad analytical range, detecting S. aureus from 1 to 10,000 CFU/mL, with a detection limit as low as 1.031 CFU/mL. Selectivity testing against Pseudomonas aeruginosa, Candida albicans, and Escherichia coli confirmed high specificity toward S. aureus. These findings highlight the potential of this MIP-based electrochemical sensor as a reliable tool for rapid bacterial detection in clinical and environmental settings. Full article

(This article belongs to the Section Polymer Applications)

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16 pages, 4000 KB

Open AccessArticle

Influence of Fabric Support on Improving the Layer-by-Layer Polyethersulfone Membrane Performance

by Ahmed A. Bhran, Abdelrahman G. Gadallah, Eman S. Mansor and Heba Abdallah

Polymers 2025, 17(21), 2825; https://doi.org/10.3390/polym17212825 - 23 Oct 2025

Abstract

This work is based on studying the effect of different kinds of support on the prepared reverse osmosis membranes. Different kinds of woven and non-woven supports were tested and characterized to select the best one for RO membrane preparation. The prepared membrane on [...] Read more.

This work is based on studying the effect of different kinds of support on the prepared reverse osmosis membranes. Different kinds of woven and non-woven supports were tested and characterized to select the best one for RO membrane preparation. The prepared membrane on polyester woven support (M1ws) provides 39.9 LMH permeate flux using a piperazine coagulation bath during membrane preparation, while polyester non-woven support (M2ns) exhibits the highest salt rejection percentage, which was 92.2% using a Melamine coagulation bath. The mechanical properties for preparing membranes using supports were arranged in descending order as follows: M1ws > M2ns > M3np. The membrane on polypropylene support (M3np) provides the lowest mechanical properties. Full article

(This article belongs to the Special Issue Preparation and Application of Polymer Membranes)

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20 pages, 7131 KB

Open AccessArticle

Design of Functional Fluorine-Containing Coatings for 3D-Printed Items

by Fedor Doronin, Georgy Rytikov, Andrey Evdokimov, Mikhail Savel’ev, Yuriy Rudyak and Victor Nazarov

Polymers 2025, 17(21), 2824; https://doi.org/10.3390/polym17212824 - 23 Oct 2025

Abstract

In this study, a surface texture design technique for 3D-extruded prototype products was developed. The study determines some target functional properties of polymer-made items. Four series of experimental samples (acrylonitrile–butadiene–styrene (ABS), thermoplastic polyurethane (TPU), polylactide (PLA), and polyethylene terephthalate glycol (PETG)) were 3D-printed [...] Read more.

In this study, a surface texture design technique for 3D-extruded prototype products was developed. The study determines some target functional properties of polymer-made items. Four series of experimental samples (acrylonitrile–butadiene–styrene (ABS), thermoplastic polyurethane (TPU), polylactide (PLA), and polyethylene terephthalate glycol (PETG)) were 3D-printed using the fused filament fabrication (FFF) approach. The morphology and hydrophilic/hydrophobic balance of the surfaces of the experimental samples were regulated directly by the 3D design and by gas-phase fluorination techniques. The observed distilled water and ethylene glycol edge wetting angles of the surfaces of the experimental samples were determined by a 3D filament stroke arrangement. It was shown that varying the 3D design promoted hydrophobization and provided anisotropic wetting (the distilled water edge angle of the same sample varies from 76 to 116 degrees). The textured surfaces simultaneously demonstrated hydrophilicity in one direction and hydrophobicity in the other. The changing of the fluorine-containing gas mixture surface treatment duration allowed us to alter the hydrophilic/hydrophobic balance of 3D-extruded prototypes. The fluorination kinetics of the experimental samples were studied empirically. The combination of macroscopic surface design (through FFF 3D printing) and microscopic surface modification (through gas-phase fluorination) permitted a significant reduction in the straining friction coefficient and increased the wettability of the complex-shaped 3D-printed products. Full article

(This article belongs to the Special Issue Polymeric Materials and Their Application in 3D Printing, 3rd Edition)

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41 pages, 12654 KB

Open AccessArticle

Study on Cooling Layer and Thin Insert Thickness Between Coolant and Cavity for Injection Mold with Bridge-Type Composite Product

by Tran Minh The Uyen, Pham Son Minh, Hung-Son Dang and Bui Chan Thanh

Polymers 2025, 17(21), 2823; https://doi.org/10.3390/polym17212823 - 23 Oct 2025

Abstract

This study focuses on the design and optimization of a cooling layer system integrated into a thin-thickness mold insert to enhance heat transfer efficiency, control mold temperature, and improve the quality of composite products during injection molding. The Taguchi method with an L25 [...] Read more.

This study focuses on the design and optimization of a cooling layer system integrated into a thin-thickness mold insert to enhance heat transfer efficiency, control mold temperature, and improve the quality of composite products during injection molding. The Taguchi method with an L25 (5⁴) orthogonal array was employed to investigate four key parameters: insert thickness, cooling layer thickness, water flow rate, and coolant temperature. Among 25 experimental combinations, five representative cases were selected for detailed analysis. The results indicate that the optimal configuration (0.5 mm insert, 10 mm cooling layer, 3.5 L/min flow rate, and 80 °C coolant temperature) successfully maintained a high and stable mold temperature, with a cavity temperature difference of only 3.6 °C at steady state and a simulation–experiment deviation ranging from 2.4% to 7.2%. This condition not only improved melt flowability and surface quality but also reduced defects such as weld lines, warpage, and shrinkage. In parallel, displacement measurements on PA6 and glass fiber-reinforced PA6 (PA6 + GF) composites revealed that increasing the fiber content from 0% to 30% reduced output displacement by more than 19% compared to neat PA6, highlighting the reinforcing effect of glass fibers and the relationship between temperature distribution and mechanical displacement behavior. The findings confirm that integrating a cooling layer into a thin-thickness mold, combined with Taguchi-based optimization, provides an effective approach to enhance through-thickness heat transfer, reduce deformation, and ensure the overall quality of composite injection-molded products in industrial applications. Full article

(This article belongs to the Special Issue Advances in Polymer Molding and Processing)

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23 pages, 4495 KB

Open AccessArticle

Transglutaminase Crosslinking Enhances Functional and Structural Properties of Fish Gelatins

by Sefik Tekle

Polymers 2025, 17(21), 2822; https://doi.org/10.3390/polym17212822 - 23 Oct 2025

Abstract

Fish gelatins are increasingly recognized as sustainable biopolymers for food, packaging, and biomedical applications; however, their functional performance often requires improvement. In this study, the effects of transglutaminase (TG) modification on the physicochemical and structural properties of trout (T) and sea bass (SB) [...] Read more.

Fish gelatins are increasingly recognized as sustainable biopolymers for food, packaging, and biomedical applications; however, their functional performance often requires improvement. In this study, the effects of transglutaminase (TG) modification on the physicochemical and structural properties of trout (T) and sea bass (SB) gelatins were systematically investigated. TG treatment enhanced gel strength in a species- and concentration-dependent manner, with trout increasing from 100 g (control) to 108 g at 0.04% TG and SB reaching a maximum of 163 g at 0.01% TG. Rheological measurements confirmed improved viscoelastic behavior, particularly in trout samples (G′ > G″). Emulsifying activity was optimized at 0.02–0.04% TG in trout, while excessive cross-linking reduced interfacial activity; nevertheless, emulsion stability was improved in both species. Foaming capacity and stability reached 195% and 148%, respectively, in trout, whereas higher TG concentrations led to reductions in SB foaming performance. Scanning electron microscopy revealed denser and more homogeneous networks in TG-modified gels, correlating with their enhanced rigidity. Transparency remained high, while zeta potential shifted toward more negative values, indicating improved colloidal stability. FTIR, UV–Vis, and DSC analyses confirmed conformational rearrangements and thermal stabilization after cross-linking. Minor decreases in oil-binding capacity and slight color changes were also observed. Overall, TG cross-linking significantly enhanced the functional and structural properties of fish gelatins in a source-dependent manner, supporting their potential as versatile and sustainable biopolymers for diverse industrial applications. Full article

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

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21 pages, 6211 KB

Open AccessArticle

Dialdehyde Cellulose Nanocrystals and Proanthocyanidins Reinforced Soy Protein Isolate Films for Blueberry Preservation

by Jiapeng Wei, Kehao Fan, Manting Meng, Zhiyong Qin and Ningjing Sun

Polymers 2025, 17(21), 2821; https://doi.org/10.3390/polym17212821 - 23 Oct 2025

Abstract

Exhibiting significant potential for sustainable packaging due to their renewability and biodegradability, soy protein isolate (SPI) films are nevertheless critically hampered by inherent brittleness, poor water resistance, and a lack of bioactivity. Herein, we demonstrate a hierarchical multi-network strategy that transforms SPI into [...] Read more.

Exhibiting significant potential for sustainable packaging due to their renewability and biodegradability, soy protein isolate (SPI) films are nevertheless critically hampered by inherent brittleness, poor water resistance, and a lack of bioactivity. Herein, we demonstrate a hierarchical multi-network strategy that transforms SPI into a high-performance, functional biocomposite. A robust covalent backbone was forged via Schiff base cross-linking between SPI and dialdehyde cellulose nanocrystals (DACNCs) derived from agricultural biomass, while proanthocyanidins (PAs) were strategically incorporated to create a secondary, pervasive hydrogen-bonding network. This hierarchical architecture effectively overcomes the typical trade-offs between mechanical strength and functionality seen in singly modified biopolymers, unlocking a suite of remarkable performance enhancements. The optimized film exhibited a 491% increase in tensile strength (to 15.54 MPa) and elevated thermal stability to 330 °C. Critically, the film was endowed with potent functionalities, including complete UV-blocking, high antioxidant capacity (93.2% ABTS scavenging), and strong, broad-spectrum antimicrobial activity. The film’s practical efficacy was validated in a preservation test, where the coating extended blueberry shelf life by inhibiting fungal spoilage and reducing weight loss by nearly 30% relative to uncoated controls after 15 days of storage. This work provides a powerful framework for developing advanced biocomposites with tailored properties for active food packaging and beyond. Full article

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

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13 pages, 1177 KB

Open AccessArticle

Dependence of Thermal Comfort of Diving Suit on Neoprene Properties and Diving Depth

by Vesna Marija Potočić Matković, Ivana Salopek Čubrić and Alenka Pavko Čuden

Polymers 2025, 17(21), 2820; https://doi.org/10.3390/polym17212820 - 23 Oct 2025

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Abstract

Neoprene wetsuits experience significant thermal resistance degradation under hydro-static pressure, compromising diver safety and thermal comfort. Despite this known limitation, quantitative predictive models correlating material properties with thermal performance under diving conditions remain underdeveloped. This study quantified thermal resistance changes in commercial neoprene [...] Read more.

Neoprene wetsuits experience significant thermal resistance degradation under hydro-static pressure, compromising diver safety and thermal comfort. Despite this known limitation, quantitative predictive models correlating material properties with thermal performance under diving conditions remain underdeveloped. This study quantified thermal resistance changes in commercial neoprene under simulated diving pressure (50, 100, 150, and 200 kPa, equivalent up to a 20 m depth) and developed predictive models for thermal performance degradation. A total of 33 commercially available neoprene sheets representing 11 types in nominal thicknesses of 3, 5, and 7 mm were systematically analyzed. Mass per unit area, thickness, and thermal resistance (R_ct) were measured under ambient conditions, as was compressive displacement under 50, 100, 150, and 200 kPa compressive loads. Multiple regression analysis established relationships between material properties and thermal performance. Under 200 kPa compression, neoprene samples exhibited compressive displacement ranging from 52.8% to 72.9% (mean: 64.3%). Strong correlations were observed between thermal resistance and thickness (r = 0.9198) and mass per unit area (r = 0.89388). The developed multiple regression model accurately predicted thermal resistance under compression. The 200 kPa pressure-induced thermal resistance reduction ranged from 19.3% to 53.2%, with an average decrease of 40.9%. Even at a pressure of 50 kPa, which corresponds to a diving depth of only 5 m, the thermal resistance of neoprene will be reduced by 21.5% on average. Commercial neoprene demonstrates substantial and predictable thermal performance degradation under diving pressure. The established correlations and predictive models enable evidence-based wetsuit selection and diving safety assessment. These findings highlight the critical need for pressure-resistant thermal insulation technologies and updated diving safety protocols accounting for depth-dependent thermal protection degradation. Full article

(This article belongs to the Special Issue Mechanical Response Characteristics and Performance Evaluation of Polymer Materials)

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Polymers, Volume 17, Issue 21 (November-1 2025) – 41 articles

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