Polymers

18 pages, 2449 KB

Open AccessArticle

Electrospun Polycaprolactone/Gelatin Blended Nanofibre Textiles with Controlled Dexamethasone Release for Anti-Inflammatory Wound Dressings

by Md Raihan Hossain, Mohammad Mahbubul Alam, Carola Esposito Corcione, Raffaella Striani and Md. Shamim Alam

Polymers 2026, 18(12), 1495; https://doi.org/10.3390/polym18121495 (registering DOI) - 14 Jun 2026

Abstract

The performance of drug-loaded electrospun nanofibres is governed not only by drug content but also by the spatial distribution of the drug within the fibre matrix, which determines release kinetics and biological response. Here, we demonstrate that dose-dependent surface crystallisation of dexamethasone (DEX) [...] Read more.

The performance of drug-loaded electrospun nanofibres is governed not only by drug content but also by the spatial distribution of the drug within the fibre matrix, which determines release kinetics and biological response. Here, we demonstrate that dose-dependent surface crystallisation of dexamethasone (DEX) in electrospun polycaprolactone (PCL)/gelatin nanofibres controls drug release behaviour and subsequent macrophage-mediated inflammation. Nanofibre mats containing 0, 1, and 2 wt% DEX (PG0, PG1, PG2) were fabricated and systematically characterised. Scanning electron microscopy revealed a change from homogeneous fibres (PG0) to surface-decorated crystalline domains with increasing drug loading, which indicates a supersaturation-driven phase separation during electrospinning. This morphological evolution directly governs the transport behaviour: PG2 exhibits a pronounced burst release due to surface-localised drug, whereas PG1 shows a balanced release profile with both surface-accessible and matrix-embedded drug fractions. Release characteristics result in different biological outcomes. PG1 and PG2 strongly inhibit pro-inflammatory cytokines (TNF-α and IL-6) in LPS-stimulated macrophages (~70–75% reduction), confirming retained drug bioactivity. However, higher drug loading (PG2) leads to lower fibroblast viability and compromised mechanical integrity. Importantly, PG1 shows a desirable balance of controlled drug release, cytocompatibility (>90% viability) and mechanical performance (~8 MPa) with effective anti-inflammatory activity. Degradation studies also show controlled structural evolution without destabilisation upon pH change, demonstrating suitability for wound environments. These results reveal surface crystallisation as an important design parameter for electrospun drug delivery systems and demonstrate that optimal therapeutic performance is controlled by intermediate drug loading, not maximum loading, providing a mechanistic framework for the rational design of immunomodulatory wound dressings. Full article

(This article belongs to the Special Issue Sustainable Biopolymer-Based Composites: Processing, Characterization and Application (3rd Edition))

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26 pages, 61419 KB

Open AccessArticle

Comparative Mechanical and Thermal Performance of Graphene- and Silver Nanoparticle-Reinforced PLA Fabricated by FDM 3D Printing

by Filiz Karabudak

Polymers 2026, 18(12), 1494; https://doi.org/10.3390/polym18121494 (registering DOI) - 14 Jun 2026

Abstract

The increasing demand for high-performance and multifunctional polymer materials has driven interest in improving the mechanical properties of polymer components produced through additive manufacturing. This study aims to systematically investigate and comparatively evaluate the effects of low-content nanofiller incorporation on the structural, thermal, [...] Read more.

The increasing demand for high-performance and multifunctional polymer materials has driven interest in improving the mechanical properties of polymer components produced through additive manufacturing. This study aims to systematically investigate and comparatively evaluate the effects of low-content nanofiller incorporation on the structural, thermal, and mechanical performance of PLA-based materials produced via fused deposition modeling (FDM), with a focus on identifying filler-dependent behavior under different loading conditions. In this study, polylactic acid (PLA) composites reinforced with 0.5 wt.% graphene (Gr) and 0.5 wt.% silver (Ag) nanoparticles, added separately, were produced using fused deposition modeling (FDM) and comparatively investigated. Each nanofiller was incorporated individually into PLA-based filaments, and standard test specimens were fabricated via 3D printing. Structural, thermal, and mechanical properties were evaluated using tensile, compressive, and three-point bending tests, along with SEM, EDS, XRD, FTIR, DSC, and TGA analyses. The results showed that pure PLA exhibited typical brittle behavior and a single-stage thermal degradation profile. The tensile strength of pure PLA was 41.93 MPa, and the flexural strength was 70.76 MPa. The addition of 0.5 wt.% graphene led to noticeable improvements, particularly in flexural properties, while only a minimal (almost negligible) increase was observed in tensile strength, with tensile strength increasing to 42.24 MPa (+0.74%) and flexural strength increasing to 110.78 MPa (+56.6%). In contrast, 0.5 wt.% Ag exhibited mixed and load-dependent mechanical behavior, with slight improvements in flexural strength but reductions in tensile and compressive properties, where tensile strength decreased to 22.13 MPa (−47.2%) while flexural strength increased to 112.06 MPa (+58.3%). Structural and thermal analyses indicated that both nanofillers did not significantly alter the PLA matrix chemically, while contributing to controlled changes in material properties primarily through physical interactions. The novelty of this work lies in the comparative evaluation of graphene and silver nanoparticle reinforcement at a fixed low loading level within FDM-processed PLA, combined with a comprehensive and correlated analysis of mechanical, structural, and thermal behavior on the same specimen sets, enabling a clearer understanding of filler-dependent performance mechanisms in additively manufactured nanocomposites. Overall, it was concluded that low-rate nanofiller additions, when properly dispersed, may lead to selective improvements in the performance of PLA-based composites depending on filler type and loading mode, and show potential for advanced engineering applications such as lightweight structural components, functional sensors, and additive-manufactured parts requiring tailored mechanical performance and multifunctionality. Full article

(This article belongs to the Special Issue Carbon Nanomaterial-Reinforced Polymer Nanocomposites: Advanced Synthesis, Properties, and Multifunctional Applications)

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22 pages, 7464 KB

Open AccessArticle

Partial Discharge Gas Generation Characteristics and Molecular Degradation Mechanisms of Cellulose Polymers in Eco-Friendly Insulating Oils

by Yiheng Zhou, Yixin He, Guangliang Liu, Xianglin Kong, Jiaming Yan and Wenyu Ye

Polymers 2026, 18(12), 1493; https://doi.org/10.3390/polym18121493 (registering DOI) - 14 Jun 2026

Abstract

Two bio-based insulating oils (BHOs) with average carbon chain lengths of approximately 18 and 22 were investigated as short- and long-chain BHOs. By constructing an oil-paper composite insulation system, the generation law of characteristic gases in the two systems was studied by partial [...] Read more.

Two bio-based insulating oils (BHOs) with average carbon chain lengths of approximately 18 and 22 were investigated as short- and long-chain BHOs. By constructing an oil-paper composite insulation system, the generation law of characteristic gases in the two systems was studied by partial discharge experiments. Based on the ReaxFF reaction molecular dynamics simulation under electrothermal coupling stress, the cracking path, cracking rate, evolution of oxygen-containing small molecules, and generation path of characteristic gases of cellulose polymer were revealed. Both systems produced H₂, CH₄, C₂H₂, C₂H₄, C₂H₆, CO, and CO₂, with CO₂ dominant and C₂H₆ least abundant. The short-chain BHO generated markedly higher amounts of H₂, CO, C₂H₂, and C₂H₄ than the long-chain BHO; after 15 min, its H₂ and CO concentrations were about 3.4- and 2.1-times those in the long-chain system, respectively. ReaxFF simulations showed that cellulose degradation in the short-chain BHO followed stepwise chain scission and continuous decarbonylation, favoring CO and unsaturated gas precursors. In contrast, cellulose chains disappeared faster in the long-chain BHO, producing more oxygen-containing organic fragments and C₁-C₅ oxygenated molecules and a higher small-molecule conversion ratio. Characteristic gas pathway analysis revealed that all seven gases could be generated from cellulose pyrolysis intermediates, and different oil environments primarily influenced gas generation behavior by altering the evolution pathways of these intermediates. These findings, at the molecular scale, elucidate the impact of BHO environments on the degradation mechanism of cellulose polymers, providing a theoretical basis for the condition assessment and design of environmentally friendly oil-paper insulation systems. Full article

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

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17 pages, 2455 KB

Open AccessArticle

Waterborne Polyurethane Reinforced with SiO₂-Modified TiO₂: Enhanced Mechanical Properties and Retained Hydrostatic Pressure Resistance

by Shuyi Wang, Weiping Yao, Xia Lin, Yamin Xu, Kemei Pei and Yuhai Lu

Polymers 2026, 18(12), 1492; https://doi.org/10.3390/polym18121492 (registering DOI) - 13 Jun 2026

Abstract

Driven by the growing demand for functional textiles featuring excellent waterproofness, moisture permeability and mechanical robustness in outdoor sportswear, medical protection and technical apparel, traditional pongee—despite its desirable softness, high wrinkle resistance and good stability as an ideal substrate fabric—is severely restricted in [...] Read more.

Driven by the growing demand for functional textiles featuring excellent waterproofness, moisture permeability and mechanical robustness in outdoor sportswear, medical protection and technical apparel, traditional pongee—despite its desirable softness, high wrinkle resistance and good stability as an ideal substrate fabric—is severely restricted in further application by its intrinsically poor hydrostatic pressure resistance in extremely wet environments. Accordingly, we developed a modified waterborne polyurethane (WPU) coating for pongee substrates to fabricate functional textiles that maintain high hydrostatic pressure resistance while possessing good mechanical properties and increased UV absorption. In this study, by using the sol–gel method, an amorphous silicon dioxide (SiO₂) coating layer was constructed on the surface of titanium dioxide (TiO₂) particles, forming silica-modified titania particles (SiO₂/TiO₂). These SiO₂-modified particles were subsequently physically blended with an anionic waterborne polyurethane system that had been previously modified with a polyester-type modifier A to enhance its hydrostatic pressure resistance. The resulting composite coating was designed to combine the high hydrostatic pressure resistance inherited from the modified WPU matrix, the mechanical reinforcement and increased UV absorption contributed by SiO₂/TiO₂, and satisfactory water repellency on fabric substrates. The results indicate that the incorporation of an appropriate amount of modifier A into the prepolymer system significantly enhances hydrostatic pressure resistance while maintaining high elongation at break. At a SiO₂/TiO₂ loading of 0.2 wt%, the composite film exhibits optimal comprehensive performance, characterized by superior mechanical properties, low water absorption, and static water contact angles exceeding 100° for coated fabrics. SiO₂/TiO₂ composite WPU coatings substantially improve hydrostatic pressure resistance across various fabrics, with 380T polyester taffeta demonstrating the best performance. This resistance remains remarkably stable after standard washing, indicating excellent wash fastness and practical applicability. Full article

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22 pages, 6437 KB

Open AccessArticle

Mechanical Properties of 3D-Printed Nylon-Based Composites Reinforced with Continuous Carbon Fiber: Effect of Reinforcement Layer Distribution

by Boyuan Ding, Jingjing Liu, Mouaz Al Kouzbary, Hanie Nadia Shasmin, Jingang Liu, Shengyan Ge and Noor Azuan Abu Osman

Polymers 2026, 18(12), 1491; https://doi.org/10.3390/polym18121491 (registering DOI) - 13 Jun 2026

Abstract

The application of continuous carbon fiber (CCF) can reinforce the mechanical properties of 3D-printed parts, but the effect of reinforcement layer distribution on composite performance remains unclear. This study investigates the effect of concentrated and separated distributions of CCF layers with different numbers [...] Read more.

The application of continuous carbon fiber (CCF) can reinforce the mechanical properties of 3D-printed parts, but the effect of reinforcement layer distribution on composite performance remains unclear. This study investigates the effect of concentrated and separated distributions of CCF layers with different numbers of reinforcement layers. Tensile and flexural tests are conducted in accordance with ASTM D5083 and ASTM D790, respectively. Under the conditions of a solid-filled matrix (Onyx) and 0° CCF deposition, both concentrated and separated CCF layers improve several mechanical properties. Compared with pure Onyx, one-layer CCF increases the tensile modulus by about six times and more than doubles the tensile strength. Increasing the CCF volume leads to further increases in these properties. With concentrated three-layer CCF, the tensile modulus and tensile strength reach 7.153 ± 0.090 GPa and 109.045 ± 5.124 MPa, respectively. For flexural properties, separated two- and three-layer CCFs significantly improve the tangent modulus of elasticity from 0.467 ± 0.106 GPa for pure Onyx to 2.246 ± 0.333 GPa and 3.394 ± 0.081 GPa, respectively. This study also compares the tensile and flexural strength-to-weight ratio of all specimen groups and analyzes the failure mechanisms based on macroscopic fracture appearance. The results can provide guidance for selecting appropriate CCF layer distribution strategies to reinforce composites in different applications. Full article

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

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29 pages, 4396 KB

Open AccessArticle

Synergistic Role of Crosslinker and Silane-Based Additive in Designing Structurally Robust Bio-Based Polyurethane Coatings

by Mayankkumar L. Chaudhary, Kinal Chaudhari, Rutu Patel and Ram K. Gupta

Polymers 2026, 18(12), 1490; https://doi.org/10.3390/polym18121490 (registering DOI) - 13 Jun 2026

Abstract

Bio-based polyurethane (PU) coatings offer sustainable alternatives to petrochemical coatings but often suffer from inferior mechanical performance, durability, and chemical resistance. This work addresses that challenge by integrating a trifunctional bio-based crosslinker (glycerol) and a silane-based additive (hexamethyldisilane (HMDS)) to simultaneously enhance structural [...] Read more.

Bio-based polyurethane (PU) coatings offer sustainable alternatives to petrochemical coatings but often suffer from inferior mechanical performance, durability, and chemical resistance. This work addresses that challenge by integrating a trifunctional bio-based crosslinker (glycerol) and a silane-based additive (hexamethyldisilane (HMDS)) to simultaneously enhance structural robustness and hydrophobicity. Coatings were synthesized using a renewable soybean oil polyol (SOP), glycerol (5, 10, 15 and 20 wt.%), and methylene diphenyl diisocyanate (MDI), followed by the addition of HMDS (10, 20, 30, 40 and 50 wt.%). Mechanical tests identified 10 wt.% glycerol as the optimal content, yielding a maximum tensile strength of 47.18 MPa. Incorporating 10 wt.% HMDS into the optimized formulation greatly increased water contact angle (WCA, 95.76°) and chemical resistance with minimal loss of mechanical performance (38.19 MPa, tensile strength); higher HMDS loadings caused network disruption and reduced strength. Calorimetry and thermogravimetric analyses confirmed that the modified coatings retained high thermal stability. This synergistic crosslinker additive strategy produced a structurally robust, water-resistant bio-based coating, demonstrating a viable high-performance sustainable coating solution for industrial applications. Full article

(This article belongs to the Special Issue Recent Advances in Polymer Coatings)

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22 pages, 10503 KB

Open AccessArticle

Green Extraction of Microcrystalline Cellulose from Rice Straw and Determination of Its Reinforcing Capacity in PHBV Films

by Pedro Augusto Vieira de Freitas, Chelo González-Martínez and Amparo Chiralt

Polymers 2026, 18(12), 1489; https://doi.org/10.3390/polym18121489 (registering DOI) - 13 Jun 2026

Abstract

Rice straw is a highly produced agricultural waste with a high cellulose content, which can be used as a cellulose source. Nevertheless, more sustainable extraction and purification strategies are needed to reduce the consumption of chemicals during the production of cellulose-derived materials. In [...] Read more.

Rice straw is a highly produced agricultural waste with a high cellulose content, which can be used as a cellulose source. Nevertheless, more sustainable extraction and purification strategies are needed to reduce the consumption of chemicals during the production of cellulose-derived materials. In this way, an integrated method based on subcritical water extraction and bleaching with hydrogen peroxide was used for isolating cellulose from rice straw. The cellulose fibres obtained were converted into microcrystalline cellulose (MCC) by applying acid hydrolysis with HCl 2N at 60 °C to reduce the fibre amorphous fraction. High cellulose purity (86%) and crystallinity (67%) were obtained in the isolated fibres. The influence of high-shear homogenisation (12,000 rpm) during hydrolysis was analysed, compared to mild stirring (350 rpm) at different times (30 and 60 min). High-shear homogenisation greatly accelerated the hydrolysis process of the amorphous fraction of the fibres, contributing to the reduction in particle size (to about 10 µm), defibration, increased crystallinity (70–72%), and shorter cellulose chains (92,400–61,600 g/mol) for a given treatment time. After 30–60 min of treatment, the resulting MCCs exhibited properties within the range reported for commercial AVICEL, with greater reinforcing performance in PHBV films. These MCCs resulted in lower water vapour permeability, while improved oxygen barrier properties were mainly observed for those obtained under high-shear hydrolysis conditions. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications, 3rd Edition)

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41 pages, 932 KB

Open AccessReview

The Mechanisms of the Initiation Step in Ring-Opening Polymerization of β-Lactones: A Review

by Zbigniew Grobelny, Sylwia Golba and Justyna Jurek-Suliga

Polymers 2026, 18(12), 1488; https://doi.org/10.3390/polym18121488 (registering DOI) - 13 Jun 2026

Abstract

Ring-opening polymerization (ROP) of β-lactones yields biodegradable and bioresorbable polyesters exhibiting potential utility in medicine and environmental protection. β-butyrolactone (BL) is especially interesting, as it yields polymers analogous to natural poly(3-hydroxybutyrates) produced by bacteria, fungi, and enzymes in nature. The biopolymer produced by [...] Read more.

Ring-opening polymerization (ROP) of β-lactones yields biodegradable and bioresorbable polyesters exhibiting potential utility in medicine and environmental protection. β-butyrolactone (BL) is especially interesting, as it yields polymers analogous to natural poly(3-hydroxybutyrates) produced by bacteria, fungi, and enzymes in nature. The biopolymer produced by these microorganisms is isotactic. While it can be synthesized biotechnologically through the bacterial fermentation of substrates, such as sucrose, corn, and sugar, laboratory production typically involves the ring-opening polymerization of BL. However, the latter process is mainly atactic, syndiotactic, or partly isotactic, and other β-substituted β-lactones are less well-known. Ring-opening polymerization is an excellent pathway for the production of poly(β-lactones). This critical review presents the different conditions required to synthesize poly(β-lactones) and a broad overview of the different kinds of ROPs, i.e., anionic, cationic, coordinative, supramolecular-based, and enzymatic processes. A great variety of initiators/catalysts have been studied, covering both metal-based and metal-free systems (organo- and biocatalysts). In this review, several mechanisms of β-lactone polymerization are presented and discussed, especially with regard to the processes’ initiation steps. Full article

(This article belongs to the Special Issue Latest Progress on Polymer Synthesis with Multifunctional Monomers)

35 pages, 7778 KB

Open AccessReview

A Review of the Application Research on Inorganic Clay Minerals Synergising with Bio-Based Flame-Retardant Systems to Enhance Polymer Performance

by Shihao Zheng, Yong Liu, Fang Zhou and Hao Yuan

Polymers 2026, 18(12), 1487; https://doi.org/10.3390/polym18121487 (registering DOI) - 13 Jun 2026

Abstract

In recent years, synergistic effects between inorganic clay minerals (e.g., montmorillonite, sepiolite, kaolinite) and bio-based flame retardants (e.g., chitosan-based, lignin-based, phytate-based) have achieved certain progress in the area of polymer flame retardancy. The effects of bio-based flame retardants are exerted through mechanisms such [...] Read more.

In recent years, synergistic effects between inorganic clay minerals (e.g., montmorillonite, sepiolite, kaolinite) and bio-based flame retardants (e.g., chitosan-based, lignin-based, phytate-based) have achieved certain progress in the area of polymer flame retardancy. The effects of bio-based flame retardants are exerted through mechanisms such as catalytic char generation and vapour-phase hindrance. However, they have limitations when used alone, including insufficient thermal stability and the need for a high dosage. Inorganic clays form physical barriers through their layered or tubular structures. The high thermal stability of these structures suppresses heat and mass transfer, thereby offsetting the shortcomings of bio-based flame retardants. This synergistic combination greatly improves the flame retardancy of polymer composites, often strengthening their mechanical performance in the process. It therefore offers great potential for the design of multifunctional, eco-friendly flame-retardant polymer composites. Nevertheless, a systematic review of the synergistic mechanisms, fabrication approaches and application progress of different inorganic clay minerals when combined with various bio-based flame retardants is still lacking. Therefore, this article offers a comprehensive review of the current developments of synergistic systems that incorporate various primary clays, such as sepiolite and montmorillonite, with bio-based flame retardants for usage in polymers. Before this, the synergistic flame-retardant mechanism and the key preparation techniques of the composite system were explained in detail. Finally, this article puts forward solutions to the current challenges and sets out prospects for innovation in the designing of flame-retardant materials and the optimisation of processes. The aim is to promote the sustainable growth of efficient, eco-friendly flame-retardant materials. Full article

(This article belongs to the Topic Functionalized Materials for Environmental Applications)

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16 pages, 1734 KB

Open AccessArticle

Influence of 3D Printer Type, Resin Material, Thickness, and Geometry on the Mechanical Properties of Directly Printed Clear Aligners

by Fırat Oğuz, Sabahattin Bor, Buse Çebi Gül and Handan Göze Oğuz

Polymers 2026, 18(12), 1486; https://doi.org/10.3390/polym18121486 (registering DOI) - 13 Jun 2026

Abstract

To evaluate the effects of three different 3D printers, two clear aligner resins, two specimen thicknesses, two lengths, and two geometric designs on the tensile strength and elastic modulus of directly printed clear aligners. Specimens were produced from two orthodontic aligner resins, Clear [...] Read more.

To evaluate the effects of three different 3D printers, two clear aligner resins, two specimen thicknesses, two lengths, and two geometric designs on the tensile strength and elastic modulus of directly printed clear aligners. Specimens were produced from two orthodontic aligner resins, Clear A (Senertek, Izmir, Turkey) and Tera Harz TA 28 (Graphy Inc., Seoul, Republic of Korea), using three different 3D printers: Ackuretta SOL (LCD), Asiga MAX (DLP), and UNIZ NBEE (LCD). Specimens were designed in two forms (dumbbell, in accordance with ISO 527 3, and flat strip), in two thicknesses (0.5 mm and 1 mm), and in two lengths (short and long), yielding 24 groups with 5 specimens each (n = 120). All specimens were post processed using the Tera Harz Spinner and cured for 25 min under nitrogen atmosphere in the THC 2 MC unit, followed by a 1 min boiling water treatment. Tensile tests were performed on a universal testing machine (Shimadzu Corp., Kyoto, Japan) up to fracture. Maximum force (N) and elastic modulus (N/mm²) were recorded. Data were analyzed using Kruskal–Wallis, Mann–Whitney U, and Aligned Rank Transform ANOVA tests with Dunn post hoc and Bonferroni correction (p < 0.05). Printer type had no significant effect on maximum force (p = 0.357) or elastic modulus (p = 0.052). Resin type (p < 0.001), thickness (p < 0.001), and specimen geometry (p < 0.001) showed significant effects on both parameters. TA 28 specimens exhibited higher mechanical performance than Clear A. Increased thickness produced higher maximum force and elastic modulus values. Flat geometries showed the highest maximum force, while the short dumbbell exhibited the lowest. The long thin dumbbell geometry yielded the highest elastic modulus values. Resin composition, thickness, and specimen geometry are the primary determinants of mechanical performance in directly printed clear aligners, whereas printer type appears to play a limited role. Full article

(This article belongs to the Section Polymer Applications)

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16 pages, 14174 KB

Open AccessArticle

From Recovery to Enhancement: Pressure-Gradient-Driven Crack Repair of Particulate-Reinforced Polymer Composites

by Shengnan Wang, Xinqiao Zhu, Wei Tang, Maoping Wen, Lingang Lan, Xin Tian and Hongwei Yuan

Polymers 2026, 18(12), 1485; https://doi.org/10.3390/polym18121485 (registering DOI) - 13 Jun 2026

Abstract

Particulate-reinforced polymer composites (PRPCs) are susceptible to cracking under tensile loading, severely limiting their service life. Here, we propose a pressure-gradient-driven infiltration method that rapidly repairs narrow (<10 μm) cracks in a highly filled PRPC (95 wt.% BaSO₄/5 wt.% fluororubber). Microstructural [...] Read more.

Particulate-reinforced polymer composites (PRPCs) are susceptible to cracking under tensile loading, severely limiting their service life. Here, we propose a pressure-gradient-driven infiltration method that rapidly repairs narrow (<10 μm) cracks in a highly filled PRPC (95 wt.% BaSO₄/5 wt.% fluororubber). Microstructural evidence confirms that the adhesive completely fills the tortuous crack and forms a continuous adhesive–matrix interface capable of supporting load transfer. Semi-circular bend (SCB) testing demonstrates a substantially higher peak load and increased apparent structural stiffness after repair under the present semi-circular bend configuration, indicating apparent mechanical enhancement beyond simple load-bearing recovery. Digital image correlation (DIC) and fracture morphology show that repair suppresses notch-tip strain localization, reduces the strain concentration factor, shifts the failure-controlling zone away from the original notch tip, and deflects the crack propagation path. Phase-field simulations further show that the post-repair load-bearing capacity is governed by the adhesive–matrix interfacial strength; once this strength approaches or exceeds the tensile strength of the intact PRPC (~8.3 MPa), the repaired crack path is stabilized, enabling peak-load enhancement while suppressing damage localization along the original crack path and shifting failure to adjacent weaker regions. Overall, this work establishes a promising crack repair approach for highly filled PRPCs, while the underlying interface-controlled mechanism provides guidance for adhesive selection and repair design. Full article

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

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28 pages, 1246 KB

Open AccessReview

Research Progress in the Preparation of Lactide

by Meiqi Tian, Yingjian Zhou, Junhao Wang, Ziqi Cai, Zhipeng Li and Zhengming Gao

Polymers 2026, 18(12), 1484; https://doi.org/10.3390/polym18121484 (registering DOI) - 12 Jun 2026

Abstract

Driven by the growing demand for sustainable polymers, polylactic acid (PLA) has attracted increasing attention due to its renewable origin and biodegradability. Lactide, the key cyclic monomer for PLA production via ring-opening polymerization (ROP), plays a decisive role in determining the molecular weight, [...] Read more.

Driven by the growing demand for sustainable polymers, polylactic acid (PLA) has attracted increasing attention due to its renewable origin and biodegradability. Lactide, the key cyclic monomer for PLA production via ring-opening polymerization (ROP), plays a decisive role in determining the molecular weight, stereoregularity, and final performance of PLA materials. However, current lactide synthesis processes still face significant challenges, including competing side reactions under high-temperature and high-vacuum conditions, difficulties in controlling stereochemical purity, and relatively high energy consumption. In this review, recent advances in lactide synthesis are systematically analyzed by examining the two principal industrial routes: the one-step process based on the direct dehydration–cyclization of lactic acid (LA), and the two-step process involving prepolymerization of LA followed by depolymerization/cyclization of oligomeric intermediates. The reaction mechanisms, key intermediates, and major side reactions—including racemization, transesterification, and deep polycondensation—are discussed, together with the regulatory roles of catalytic systems and reaction–separation coupling strategies. Comparative analysis reveals that the one-step route offers advantages in process integration and potential energy efficiency, whereas the two-step route provides superior control over stereochemical purity and process stability. Future research directions focusing on green catalysts, process intensification, and sustainable lactide production are also highlighted. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Environmental Assessment of Novel Polymeric Materials for Sustainable Applications)

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27 pages, 7702 KB

Open AccessArticle

Valorization of Keratin Waste as a Functional Precursor for PLA/SBS Composite Adsorbent Films

by Maria Râpă, Raluca Nicoleta Darie-Niță, Andra Mihaela Predescu, Augusta Raluca Gabor, Cristian-Andi Nicolae, Carmen Gaidău, Corina Violeta Chiriță, Ramona Eugenia Popescu and Laurențiu Dincă

Polymers 2026, 18(12), 1483; https://doi.org/10.3390/polym18121483 (registering DOI) - 12 Jun 2026

Abstract

This study investigated the valorization of keratin extracted from sheep wool waste for the preparation of PLA/SBS/Keratin composites as potential adsorbents for the removal of chromium (Cr) from synthetic water. A flexible formulation containing 75 wt% PLA and 25 wt% SBS was selected [...] Read more.

This study investigated the valorization of keratin extracted from sheep wool waste for the preparation of PLA/SBS/Keratin composites as potential adsorbents for the removal of chromium (Cr) from synthetic water. A flexible formulation containing 75 wt% PLA and 25 wt% SBS was selected for the incorporation of 10 wt%, 20 wt%, and 30 wt% keratin. The morphology and structural characteristics of keratin and PLA-based composites were analyzed using SEM and FT-IR spectroscopy. The mechanical and thermal properties of the prepared composites were investigated using TGA and DMA analyses. The adsorption experiments revealed that keratin exhibited an adsorption capacity of 57.57 mg g⁻¹ of Cr(VI) removal efficiency, while the PLA/SBS formulation containing 10 wt% keratin achieved a removal efficiency of total Cr of 55.41%. After three regeneration cycles, the removal efficiency decreased by approximately half of the total Cr removal. Full article

(This article belongs to the Special Issue Polyester-Based Materials: 3rd Edition)

20 pages, 11611 KB

Open AccessArticle

Molecularly Imprinted Membranes: From Protein Recognition to Refolding Activity

by Norma Mallegni, Niccoletta Barbani, Dawid Rossino, Francesca Cicogna and Caterina Cristallini

Polymers 2026, 18(12), 1482; https://doi.org/10.3390/polym18121482 (registering DOI) - 12 Jun 2026

Abstract

Molecular imprinting is a powerful strategy for fabricating synthetic materials with selective recognition toward specific biomolecules. In this work, molecularly imprinted (MIM) membranes based on poly (ethylene-co-vinyl alcohol) (EVAL) were developed for selective protein recognition and conformational modulation using α-amylase as a model [...] Read more.

Molecular imprinting is a powerful strategy for fabricating synthetic materials with selective recognition toward specific biomolecules. In this work, molecularly imprinted (MIM) membranes based on poly (ethylene-co-vinyl alcohol) (EVAL) were developed for selective protein recognition and conformational modulation using α-amylase as a model template. Membranes were prepared by phase inversion, generating porous structures suitable for mass transport and adsorption. Template extraction, measured using UV–Vis spectroscopy, showed a rapid and effective removal of α-amylase while preserving membrane morphology, as confirmed by SEM. FTIR-ATR and chemical imaging confirmed template removal from the membrane and a uniform surface distribution of rebound α-amylase after successive template incubation. Rebinding experiments showed a concentration-dependent uptake of α-amylase and an apparent saturation trend at higher concentrations. Selectivity tests using bovine serum albumin as an analog confirmed preferential recognition of α-amylase. Enzymatic assays showed partial recovery of catalytic activity after rebinding of thermally denatured α-amylase, indicating that imprinted cavities may promote protein conformational reorganization. These results highlight the potential of EVAL-based imprinted membranes as biomimetic platforms for selective protein recognition and functional modulation. Full article

(This article belongs to the Section Polymer Membranes and Films)

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44 pages, 7643 KB

Open AccessArticle

Multi-PCM Lime Mortars Incorporating Polymer-Shell and Form-Stable Phase Change Materials for Energy-Efficient Building Envelopes

by Andrea Rubio-Aguinaga, Loucas Kyriakou, José María Fernández, Íñigo Navarro-Blasco and José Ignacio Álvarez

Polymers 2026, 18(12), 1481; https://doi.org/10.3390/polym18121481 (registering DOI) - 12 Jun 2026

Abstract

This study investigates the design and performance of lime mortars incorporating multi-phase change material (multi-PCM) systems as thermally responsive rendering materials for building-envelope applications under variable conditions. Moving beyond conventional single-PCM lime mortar approaches, this work proposes a controlled multi-PCM design framework in [...] Read more.

This study investigates the design and performance of lime mortars incorporating multi-phase change material (multi-PCM) systems as thermally responsive rendering materials for building-envelope applications under variable conditions. Moving beyond conventional single-PCM lime mortar approaches, this work proposes a controlled multi-PCM design framework in which a fixed total PCM dosage is distributed across selected phase-transition windows. Mortars combining PCMs with different transition temperatures (5–25 °C and 18–25 °C) were produced using two PCM types: silica-supported form-stable systems and polymeric-shell microencapsulated systems supplied as powders or aqueous slurries. All formulations contained 20% PCM and were optimized with polymeric additives, including a polycarboxylate ether-based superplasticiser and a starch-derived adhesion enhancer, to ensure suitable workability and applicability as rendering materials. Microstructural analyses showed that form-stable PCMs generated more heterogeneous pore structures, whereas polymeric-shell microencapsulated systems maintained pore structures similar to PCM-free mortars. Mortars containing metakaolin exhibited enhanced mechanical performance and durability, in some cases outperforming reference mortars, highlighting the importance of matrix refinement in the successful incorporation of multi-PCM systems. Thermal characterization revealed that form-stable systems produced broader phase transitions due to component interactions, while polymeric-shell microencapsulation preserved distinct transitions and enabled a wider, more controllable activation range. Under dynamic thermal conditions (−10 to 50 °C), all multi-PCM mortars demonstrated effective temperature buffering, achieving reductions of up to 1.5 °C during heating and 1.1 °C during cooling. Environmental and economic analyses highlighted that the benefits of PCM incorporation depend on matching PCM transition temperatures to specific climatic and application requirements. These findings position multi-PCM lime mortars as a promising route towards climate-adapted, thermally responsive renders with distributed and tailorable activation profiles. Full article

(This article belongs to the Section Polymer Applications)

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29 pages, 2816 KB

Open AccessArticle

Experimental Study and Numerical Modeling of Thermoviscoelastic Behavior of Antifriction Polymeric Materials

by Anna A. Kamenskikh, Anastasia P. Bogdanova, Yuriy O. Nosov and Yulia S. Kuznetsova

Polymers 2026, 18(12), 1480; https://doi.org/10.3390/polym18121480 (registering DOI) - 12 Jun 2026

Abstract

Five modifications of polytetrafluoroethylene (PTFE) are considered as a modern alternative to PTFE as sliding layers of bridge bearing parts. Radiation-modified PTFE without additives and with nano-additives as well as composites based on PTFE with bronze inclusions and nanomodified carbon fiber fillers were [...] Read more.

Five modifications of polytetrafluoroethylene (PTFE) are considered as a modern alternative to PTFE as sliding layers of bridge bearing parts. Radiation-modified PTFE without additives and with nano-additives as well as composites based on PTFE with bronze inclusions and nanomodified carbon fiber fillers were investigated. Ultra-high-molecular-weight polyethylene (UHMWPE) and classic pure PTFE were considered as control samples. The thermomechanical properties of the materials were studied within the framework of dynamic mechanical analysis in the operating temperature range of bridge structures [−40; +80] °C. The exit zones from the linear theory of viscoelasticity were established for all the materials considered. Temperature dependencies of the storage modulus and the loss modulus were determined. Thermoviscoelastic models of material behavior were constructed using a numerical identification procedure, experimental data, and simulation models. The thermomechanics of materials during the deformation of the spherical support part of the bridge were analyzed. Temperature dependencies of the parameters of the contact stress-strain state were determined with an average coefficient of determination R² = 0.97 and an average error size RMSE = 0.092. Full article

(This article belongs to the Special Issue Mechanical Behavior of Polymer Materials and Its Applications)

30 pages, 10103 KB

Open AccessReview

Fresh-State Characteristics of Geopolymer Mortars for 3D Printing: Mix Design, Rheology and Early-Age Performance

by İbrahim Türkmen, Enes Ekinci, Fatih Kantarci, Ergun Ekinci, Abdulrahman Ahmad Alyamani, Mehmet Burhan Karakoc, Ramazan Demirboğa and Yasar Ayaz

Polymers 2026, 18(12), 1479; https://doi.org/10.3390/polym18121479 (registering DOI) - 12 Jun 2026

Abstract

The successful application of extrusion-based 3D-printed geopolymer mortars largely depends on precursor chemistry, activator composition, mixture proportions, and fresh-state behavior, which is highly sensitive to time-dependent structural build-up. This review examines the relationships among mix design, geopolymerization chemistry, rheological properties, and printability requirements [...] Read more.

The successful application of extrusion-based 3D-printed geopolymer mortars largely depends on precursor chemistry, activator composition, mixture proportions, and fresh-state behavior, which is highly sensitive to time-dependent structural build-up. This review examines the relationships among mix design, geopolymerization chemistry, rheological properties, and printability requirements for 3D-printed geopolymer mortars. Particular emphasis is placed on the effects of precursor type, alkaline activator characteristics, liquid-to-solid ratio, additives, and fibers on flowability, yield stress, viscosity, extrudability, buildability, shape retention, and interlayer bonding. The review further discusses how geopolymerization kinetics influence the evolution of fresh-state properties, the printable time window, and the transition from extrusion to structural stability. In addition, early-age performance is evaluated in terms of setting behavior, green strength development, and layer-interface integrity. Current challenges, including the lack of standardized test methods, limited comparability among published studies, and the complex coupling between material design and process parameters, are also highlighted. Finally, the review identifies key research gaps and proposes future directions for developing robust, printable, and sustainable geopolymer mortar systems for additive manufacturing in construction. Full article

(This article belongs to the Special Issue Design and Analysis of Inorganic-Polymer Composite Materials for Circular Economy)

17 pages, 4275 KB

Open AccessArticle

A MOORA-Based Evaluation of Printed Conductive Fabrics for E-Textile Product Design

by Elanur Demirci, Meltem Tekcin, Ismet Ege Kalkan, Esra Akgül, Elcin Emekdar-Karaman, Umut Kivanc Sahin, Simge Ozkayalar and Serhat Karakaya

Polymers 2026, 18(12), 1478; https://doi.org/10.3390/polym18121478 (registering DOI) - 12 Jun 2026

Abstract

Electronic textiles (e-textiles) have gained significant importance due to their potential to enable wearable electronic systems. Conductive pathways in textiles can be fabricated using various approaches; among these, printing technologies stand out for their cost-effectiveness and suitability for rapid design customization. In this [...] Read more.

Electronic textiles (e-textiles) have gained significant importance due to their potential to enable wearable electronic systems. Conductive pathways in textiles can be fabricated using various approaches; among these, printing technologies stand out for their cost-effectiveness and suitability for rapid design customization. In this study, conductive patterns were produced on 100% cotton woven fabrics using rotary screen printing with different conductive paste formulations and printing layer configurations. The electrical resistance, fabric thickness, microscopic surface morphology, tensile strength, elongation, and tearing strength of the printed e-textiles were evaluated. Results indicated that resistance decreased with increasing printed track width and number of printed layers, with samples A4 and A5 exhibiting the highest conductivity. Thickness measurements and microscopic surface images showed that repeated printing increased layer build-up and surface coverage, particularly for A3 and A4. Mechanical performance tests revealed reductions in tensile strength, elongation, and tear strength after printing, attributed to restricted fiber mobility caused by the conductive paste and curing process. Despite these reductions, the mechanical property losses remained within acceptable limits for wearable applications. To determine the most suitable conductive textile for use in electronic textile product design, the Multi-Objective Optimization on the Basis of Ratio Analysis (MOORA) method, a multi-criteria decision-making (MCDM) approach, was applied using mechanical performance criteria. Electrical resistance was evaluated separately as a functional performance indicator and interpreted together with the MOORA-based mechanical ranking. Considering both mechanical and electrical performance, sample A5 was identified as the optimal alternative. Overall, this study demonstrates that printed conductive textiles can be systematically evaluated and ranked using a multi-criteria decision-making approach for material selection in wearable electronics. Full article

(This article belongs to the Special Issue Advances in Polymers-Based Functional and Smart Textiles)

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25 pages, 14019 KB

Open AccessArticle

Overcoming Impediments to the Qualification of Additively Manufactured Polymer Components: The Case of ULTEM

by Colin Marquis, Vanessa Bradshaw, Anushka Sarode, Megan Hong, Lars Glaesner, Ellen Ma, Mark Sorna and Dwayne Arola

Polymers 2026, 18(12), 1477; https://doi.org/10.3390/polym18121477 - 12 Jun 2026

Abstract

The qualification of additively manufactured (AM) components produced from engineering polymers poses unique challenges, particularly when evaluating mechanical properties according to ASTM D638. The application of high-performance thermoplastics, such as ULTEM™ 9085 and ULTEM™ 1010, frequently relies on manufacturer-provided datasheets for qualification. However, [...] Read more.

The qualification of additively manufactured (AM) components produced from engineering polymers poses unique challenges, particularly when evaluating mechanical properties according to ASTM D638. The application of high-performance thermoplastics, such as ULTEM™ 9085 and ULTEM™ 1010, frequently relies on manufacturer-provided datasheets for qualification. However, existing datasheets do not provide guidance specific to articles printed in the XY plane, which can be complicated by failures that initiate at microstructural anomalies rather than being driven by intrinsic material behavior. The objective of this study was to investigate the performance and qualification of ULTEM 9085™, examined according to ASTM D638, and pursue improvements through refined print parameters. A significant improvement in strength and conforming failures was achieved with modest adjustments to the print settings. For Type 1 samples printed with ±45° infill, gage section failures improved from only 5% to 100%, while samples with 0/90° infill achieved 80%. Correspondingly, the ultimate tensile strength increased from 49 ± 2 MPa to 61 ± 2 MPa and from 53 ± 3 MPa to 63 ± 6 MPa, respectively. These results underscore the critical role of process parameters, including contour overlap, in qualifying polymer AM materials, and their contribution to the performance and reliability of printed components. Full article

(This article belongs to the Special Issue Sustainable Polymers for 3D Printing: Design, Processing, and Applications)

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