Polymers

28 pages, 2427 KB

Open AccessArticle

Durability and Microstructural Evaluation of Geopolymer Mortars Exposed to Sulphuric Acid Using Industrial By-Product Fillers

by Ouiame Chakkor

Polymers 2025, 17(17), 2310; https://doi.org/10.3390/polym17172310 (registering DOI) - 26 Aug 2025

Abstract

Rapid urbanization and industrialization have increased atmospheric pollution, particularly via sulfur oxides (SO_x) that form sulfuric acid and accelerate the degradation of cementitious materials. While Portland-cement systems have been widely studied, less is known about the acid resistance of geopolymer mortars. [...] Read more.

Rapid urbanization and industrialization have increased atmospheric pollution, particularly via sulfur oxides (SO_x) that form sulfuric acid and accelerate the degradation of cementitious materials. While Portland-cement systems have been widely studied, less is known about the acid resistance of geopolymer mortars. This study investigates the durability and microstructural evolution of metakaolin–red mud geopolymer mortars incorporating limestone, marble, and basalt powders as partial sand replacements (5, 10, and 15 wt %). Specimens were immersed in 3% H₂SO₄ for 30, 60, and 90 days, with performance evaluated via compressive and flexural strength, weight loss, and ultrasonic pulse velocity (UPV), alongside scanning electron microscopy (SEM), x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). After 90 days, the optimal basalt-filled mix (15 wt %) retained 84% of its initial compressive strength (46.8 MPa), compared with 61% for the control; mass loss decreased from 6.4% (control) to 3.2%, and UPV degradation was reduced by 35%. Microstructural analyses indicate denser gel phases and reduced microcracking in basalt- and marble-filled mixes. These results demonstrate that industrial by-product fillers can significantly improve sulfuric-acid resistance while supporting more sustainable binder technology. Full article

(This article belongs to the Special Issue Application of Polymers in Cementitious Materials)

27 pages, 5694 KB

Open AccessArticle

Shock Response Characteristics and Equation of State of High-Mass-Fraction Pressed Tungsten Powder/Polytetrafluoroethylene-Based Composites

by Wei Zhu, Weihang Li, Wenbin Li, Xiaoming Wang and Wenjin Yao

Polymers 2025, 17(17), 2309; https://doi.org/10.3390/polym17172309 (registering DOI) - 26 Aug 2025

Abstract

Tungsten powder/polytetrafluoroethylene (W/PTFE) composites have the potential to replace traditional metallic materials as casings for controllable power warheads. Under explosive loading, they generate high-density and relatively uniformly distributed metal powder particles, thereby enhancing close-range impact effects while reducing collateral damage. To characterize the [...] Read more.

Tungsten powder/polytetrafluoroethylene (W/PTFE) composites have the potential to replace traditional metallic materials as casings for controllable power warheads. Under explosive loading, they generate high-density and relatively uniformly distributed metal powder particles, thereby enhancing close-range impact effects while reducing collateral damage. To characterize the material’s response under impact loading, plate impact tests were conducted to investigate the effects of tungsten content (70 wt%, 80 wt%, and 90 wt%) and tungsten particle size (200 μm, 400 μm, and 600 μm) on the impact behavior of the composites. The free surface velocity histories of the target plates were measured using a 37 mm single-stage light gas gun and a full-fiber laser interferometer (DISAR), enabling the determination of the shock velocity–particle velocity relationship to establish the equation of state. Experimental data show a linear relationship between shock velocity and particle velocity, with the 80 wt% and 90 wt% composites exhibiting similar shock velocities. The fitted slope increases from 2.792 to 2.957 as the tungsten mass fraction rises from 70 wt% to 90 wt%. With particle size increasing from 200 μm to 600 μm, the slope decreases from 3.204 to 2.756, while c₀ increases from 224.7 to 633.3. Comparison of the Hugoniot pressure curves of different specimens indicated that tungsten content significantly affects the impact behavior, whereas variations in tungsten particle size have a negligible influence on the Hugoniot pressure. A high tungsten content with small particle size (e.g., 90 wt% with ~200 μm) improves the overall compressive properties of composite materials. Based on the experimental results, a mesoscale finite element model consistent with the tests was developed. The overall error between the numerical simulations and experimental results was less than 5% under various conditions, thereby validating the accuracy of the model. Numerical simulations revealed the coupling mechanism between tungsten particle plastic deformation and matrix flow. The strong rarefaction unloading effect initiated at the composite’s free surface caused matrix spallation and jetting. Multiple wave systems were generated at the composite–copper interface, whose interference and coupling ultimately resulted in a nearly uniform macroscopic pressure field. Full article

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

18 pages, 33851 KB

Open AccessArticle

Wheat Straw Lignin Nanoparticles as Active Filler in Thermoplastic Starch Films

by Florian Zikeli, Franco Dominici, Marco Rallini, Sebastian Serna-Loaiza, Walter Wukovits, Anton Friedl, Michael Harasek, Luigi Torre and Debora Puglia

Polymers 2025, 17(17), 2308; https://doi.org/10.3390/polym17172308 (registering DOI) - 26 Aug 2025

Abstract

Starch and lignin are promising biopolymers for the production of biodegradable biocomposite materials. The possibility of processing starch into thermoplastic materials qualifies it as a starting material for the preparation of thermoplastic packaging films, and the combination with lignin can even out some [...] Read more.

Starch and lignin are promising biopolymers for the production of biodegradable biocomposite materials. The possibility of processing starch into thermoplastic materials qualifies it as a starting material for the preparation of thermoplastic packaging films, and the combination with lignin can even out some inherent weak points of starch, such as moisture and water sensitivity, and can add additional features like antioxidant activity. Lignins from herbaceous biomass carry building blocks that are not found in wood lignins and are known for their bioactivity, such as p-coumaric acid or ferulic acid. In this work, a protocol was developed to initially prepare hybrids of wheat starch granules and lignin nanoparticles, which were then plasticized using glycerol in an extrusion process to produce thin films. The lignin-containing thermoplastic starch films showed higher Young’s moduli and less elongation at break compared to neat thermoplastic starch films, while tensile strength remained at the level of the neat films. Thermal stability was slightly increased by lignin addition, and oxygen transmission rates were low for lignin contents as low as 1 wt%. The hydrophobicity of the lignin-containing films increased strongly, and they showed an elevated antioxidant activity over several hours, which was also maintained after 24 h. The preparation of hybrid wheat starch lignin particles was successfully tested for the extrusion of thermoplastic starch films with improved thermomechanical properties, decreased water sensitivity, and prolonged antioxidant activity. Full article

(This article belongs to the Special Issue Advanced Study on Lignin-Containing Composites)

25 pages, 5646 KB

Open AccessArticle

Isolation of Cellulose Nanofibers from Kombucha Beverage By-Product by Chemo-Mechanical Routes

by Cătălina-Diana Uşurelu, Gabriela-Mădălina Oprică, Denis Mihaela Panaitescu, Adriana Nicoleta Frone, Celina Maria Damian, Cristian Andi Nicolae, Ştefan-Ovidiu Dima, Florin Oancea and Mircea Teodorescu

Polymers 2025, 17(17), 2307; https://doi.org/10.3390/polym17172307 - 26 Aug 2025

Abstract

In a world where the negative consequences of natural resources’ overexploitation for the environment are increasingly evident, repurposing waste to obtain high-value goods becomes essential. This study proposes the isolation of cellulose nanofibers from the bacterial cellulose (BC) membrane that results as a [...] Read more.

In a world where the negative consequences of natural resources’ overexploitation for the environment are increasingly evident, repurposing waste to obtain high-value goods becomes essential. This study proposes the isolation of cellulose nanofibers from the bacterial cellulose (BC) membrane that results as a by-product during the fermentation of Kombucha tea by chemical treatment with sodium hydroxide (NaOH), sodium hypochlorite (NaClO), hydrogen peroxide (H₂O₂), sulfuric acid (H₂SO₄) or citric acid, followed by mechanical fibrillation via high-speed homogenization and microfluidization. Treatments with NaOH, NaClO, and H₂O₂ were effective in the purification of Kombucha-derived BC, while H₂SO₄ and citric acid exhibited a rather weak cleaning action, as revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Besides their cleaning effect, the applied chemical pretreatments had an important effect on the degree of fibrillation attained, as indicated by the scanning electron microscopy images. This study proposes simple and effective routes to obtain bacterial cellulose nanofibers from an inexpensive and abundant source, commonly regarded as a waste material, which can be further applied in medical and packaging applications as reinforcing agents, adsorbent materials, or scaffolds. Full article

(This article belongs to the Special Issue New Progress in the Polymer-Based Biomaterials)

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14 pages, 5648 KB

Open AccessArticle

Design and Fabrication of High-Temperature-Resistant Poly(4-methyl-1-pentene) Loaded with Tungsten and Boron Carbide Particles Against Neutron and Gamma Rays

by Ming Yu, Fan Luo, Xiaoling Li, Xianglei Chen and Zhirong Guo

Polymers 2025, 17(17), 2306; https://doi.org/10.3390/polym17172306 - 26 Aug 2025

Abstract

A novel high-temperature-resistant W-B₄C-poly(4-methyl-1-pentene) (PMP) composite shielding material against neutron and gamma rays was developed and fabricated. Firstly, utilizing the ²³⁵U-induced fission spectrum as the source term, the compositional ratio of the W-B₄C-PMP ternary composite was optimized using [...] Read more.

A novel high-temperature-resistant W-B₄C-poly(4-methyl-1-pentene) (PMP) composite shielding material against neutron and gamma rays was developed and fabricated. Firstly, utilizing the ²³⁵U-induced fission spectrum as the source term, the compositional ratio of the W-B₄C-PMP ternary composite was optimized using the genetic algorithm-based GENOCOPIII program coupled with MCNP simulations. Then, the composite was fabricated through coupling agent modification, melt mixing, and hot pressing. Finally, the effects of coupling modification and tungsten content on the thermomechanical properties of the composite were investigated. Results demonstrated that functional groups from the silane coupling agent KH550 were successfully grafted onto the filler surfaces. For composites containing 30 wt% modified B₄C and 40 wt% modified W in the PMP matrix, the heat deflection temperature (HDT) increased by 18.5% and 19.1%, respectively, compared to their unmodified counterparts. The impact strength also improved by 31.6% and 5.0%, respectively. The variation trend of the composite’s modulus approximately followed the classical Einstein model, while its tensile strength and flexural strength conformed precisely to the model:

\frac{σ_{c}}{σ_{m}} = 0.88 V_{f}^{- 0.02}

. Thermal analysis indicated that the composites possessed a melting point exceeding 230 °C, and their thermal stability improved with increasing filler content. Full article

(This article belongs to the Section Polymer Applications)

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19 pages, 11547 KB

Open AccessArticle

Impact of Polymer Molecular Weight on Aging of Poly(Ethyleneoxide)/Dextran All-Aqueous Emulsions Stabilized by Oppositely Charged Nanoparticle/Polyelectrolyte Assemblies

by Attila Kardos, Mónika Bak, Emese Kovács, György Juhász, Mihály Cserepes, József Tóvári and Róbert Mészáros

Polymers 2025, 17(17), 2305; https://doi.org/10.3390/polym17172305 - 26 Aug 2025

Abstract

Aqueous two-phase systems (ATPSs) based on two incompatible polymers have recently garnered considerable attention due to the promising characteristics of all-aqueous emulsions for a range of applications. Recent investigations have indicated strong potential for interfacial assemblies of oppositely charged components in the stabilization [...] Read more.

Aqueous two-phase systems (ATPSs) based on two incompatible polymers have recently garnered considerable attention due to the promising characteristics of all-aqueous emulsions for a range of applications. Recent investigations have indicated strong potential for interfacial assemblies of oppositely charged components in the stabilization of these emulsions. The formation of these confined assemblies is likely to depend on the size of the ATPS-constituting polymers; however, the role of this parameter remains to be elucidated. The primary objective of this study was to examine the effect of polyethylene oxide (PEO) molecular weight on the aging processes of PEO/dextran emulsions that are stabilized by the interfacial association of oppositely charged silica particles and polycations. It has been demonstrated that the stability of emulsions containing one high-molecular-weight dextran is significantly enhanced by increasing the size of the PEO molecules. Furthermore, a compression-induced bijel formation was observed in the ATPS with the largest molecular weight PEO sample. The observations were explained by the impact of the rheology of the aqueous phases on the aggregation, adsorption, and network formation capabilities of polycation/silica assemblies. These findings may facilitate the design of stable all-aqueous emulsions with optimal molecular weights for the ATPS-forming polymers. Full article

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17 pages, 12273 KB

Open AccessArticle

Mechanical Characterization of Graphene-Enhanced Fiber Rope Composites for Strengthening-Oriented Applications

by Ahmet E. Haberdar, Volkan Acar and Ferit Cakir

Polymers 2025, 17(17), 2304; https://doi.org/10.3390/polym17172304 - 26 Aug 2025

Abstract

Achieving high mechanical performance in fiber-reinforced composites is essential for developing reliable and sustainable strengthening systems that aim to enhance service life and reduce the waste of resources. In particular, fiber rope composites, with their inherent flexibility and excellent structural properties, offer significant [...] Read more.

Achieving high mechanical performance in fiber-reinforced composites is essential for developing reliable and sustainable strengthening systems that aim to enhance service life and reduce the waste of resources. In particular, fiber rope composites, with their inherent flexibility and excellent structural properties, offer significant potential as reinforcement elements in strengthening applications. The mechanical properties of these composites could be further enhanced using a remarkably basic and fundamental method. In this study, this fundamental and effective method, nanoparticle modification, is presented at its most basic level. This research presents an experimental investigation into the mechanical behavior of 8 mm diameter carbon, basalt, and glass fiber rope composites, produced in both unmodified and graphene nanoplatelet (GNP)-modified forms. GNPs were reinforced into an epoxy matrix at weight fractions of 0.5%, 1%, and 2% to enhance the mechanical properties of the fiber rope composites. Fiber rope composites were fabricated using controlled mixing, molding, and curing techniques. Subsequently, a series of mechanical tests, including flexural, compressive, and buckling tests, were conducted to evaluate the impact of nanoparticle reinforcement on structural performance. The findings reveal that GNP modification leads to notable improvements in mechanical properties, suggesting that such enhanced composites may contribute to more resilient and long-lasting strengthening solutions. These results underscore the relevance of nanoparticle-enhanced composites in the context of material efficiency and end-of-life considerations in structural systems, particularly through extended usability and improved performance. Full article

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35 pages, 1429 KB

Open AccessReview

Progressive Hydrogel Applications in Diabetic Foot Ulcer Management: Phase-Dependent Healing Strategies

by Priyanka Mallanagoudra, Sai Samanvitha M Ramakrishna, Sowmya Jaiswal, Dhruthi Keshava Prasanna, Rithika Seetharaman, Arunkumar Palaniappan and Sudarshan Kini

Polymers 2025, 17(17), 2303; https://doi.org/10.3390/polym17172303 - 26 Aug 2025

Abstract

Diabetes is emerging as a significant health and societal concern globally, impacting both young and old populations. In individuals with diabetic foot ulcers (DFUs), the wound healing process is hindered due to abnormal glucose metabolism and chronic inflammation. Minor injuries, blisters, or pressure [...] Read more.

Diabetes is emerging as a significant health and societal concern globally, impacting both young and old populations. In individuals with diabetic foot ulcers (DFUs), the wound healing process is hindered due to abnormal glucose metabolism and chronic inflammation. Minor injuries, blisters, or pressure sores can develop into chronic ulcers, which, if left untreated, may lead to serious infections, tissue necrosis, and eventual amputation. Current management techniques include debridement, wound dressing, oxygen therapy, antibiotic therapy, topical application of antibiotics, and surgical skin grafting, which are used to manage diabetic wounds and foot ulcers. This review focuses on a hydrogel-based strategy for phase-wise targeting of DFUs, addressing sequential stages of diabetic wound healing: hemostasis, infection, inflammation, and proliferative/remodeling phases. Hydrogels have emerged as a promising wound care solution due to their unique properties in providing a suitable wound-healing microenvironment. We explore natural polymers, including hyaluronic acid, chitosan, cellulose derivatives, and synthetic polymers such as poly (ethylene glycol), poly (acrylic acid), poly (2-hydroxyethyl methacrylate, and poly (acrylamide), emphasizing their role in hydrogel fabrication to manage DFU through phase-dependent strategies. Recent innovations, including self-healing hydrogels, stimuli-responsive hydrogels, nanocomposite hydrogels, bioactive hydrogels, and 3D-printed hydrogels, demonstrate enhanced therapeutic potential, improving patient outcomes. This review further discusses the applicability of various hydrogels to each phase of wound healing in DFU treatment, highlighting their potential to advance diabetic wound care through targeted, phase-specific interventions. Full article

(This article belongs to the Special Issue Advances in Biomimetic Smart Hydrogels)

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18 pages, 1884 KB

Open AccessArticle

Additive Manufacturing of Regorafenib Tablets: Formulation Strategies and Characterization for Colorectal Cancer

by Fatemeh Safari, Azin Goudarzi, Hossein Abolghasemi, Hussein Abdelamir Mohammad, Mohammad Akrami, Saeid Mohammadi and Ismaeil Haririan

Polymers 2025, 17(17), 2302; https://doi.org/10.3390/polym17172302 - 26 Aug 2025

Abstract

Significant efforts have been dedicated to developing controlled-release systems for the effective management of colorectal cancer. In this study, a once-daily, delayed-release regorafenib (REG) tablet was fabricated using 3D printing technology for the treatment of colorectal cancer. For this, a hydrogel containing 80 [...] Read more.

Significant efforts have been dedicated to developing controlled-release systems for the effective management of colorectal cancer. In this study, a once-daily, delayed-release regorafenib (REG) tablet was fabricated using 3D printing technology for the treatment of colorectal cancer. For this, a hydrogel containing 80 mg of the drug in a matrix of hyaluronic acid, carboxymethyl cellulose, Pluronic F127, and glycerol was prepared to incorporate into the shell cavity of tablet via a pressure-assisted microsyringe (PAM). The shell was printed from an optimized ink formulation of Soluplus^®, Eudragit^® RS-100, corn starch 1500, propylene glycol 4000, and talc through melt extrusion-based 3D printing. In vitro release assays showed a drug release rate of 91.1% in the phosphate buffer medium at 8 h and only 8.5% in the acidic medium. Drug release kinetics followed a first-order model. The results showed smooth and uniform layers based on scanning electron microscopy (SEM) and drug stability at 135 °C upon TGA. FTIR analysis confirmed the absence of undesired covalent interactions between the materials. Weight variation and assay results complied with USP standards. Mechanical strength testing revealed a Young’s modulus of 5.18 MPa for the tablets. Overall, these findings demonstrate that 3D printing technology enables the precise fabrication of delayed-release REG tablets, offering controlled-release kinetics and accurate dosing tailored for patients in intensive care units. Full article

(This article belongs to the Special Issue Polymeric Materials for 3D Printing)

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22 pages, 6017 KB

Open AccessArticle

Expandable Gastroretentive Films Based on Anthocyanin-Rich Rice Starch for Improved Ferulic Acid Delivery

by Nattawipa Matchimabura, Jiramate Poolsiri, Nataporn Phadungvitvatthana, Rachanida Praparatana, Ousanee Issarachot and Ruedeekorn Wiwattanapatapee

Polymers 2025, 17(17), 2301; https://doi.org/10.3390/polym17172301 - 25 Aug 2025

Abstract

Ferulic acid (FA) is a bioactive compound known for its potent antioxidant and anti-inflammatory properties; however, its poor water solubility significantly limits its bioavailability and therapeutic potential. In this study, a solid dispersion of FA (FA-SD) was developed using Eudragit^® EPO via [...] Read more.

Ferulic acid (FA) is a bioactive compound known for its potent antioxidant and anti-inflammatory properties; however, its poor water solubility significantly limits its bioavailability and therapeutic potential. In this study, a solid dispersion of FA (FA-SD) was developed using Eudragit^® EPO via the solvent evaporation method, achieving a 24-fold increase in solubility (42.7 mg/mL) at a 1:3 drug-to-polymer ratio. Expandable gastroretentive films were subsequently formulated using starches from Hom-Nil rice, glutinous rice, and white rice, combined with chitosan as the primary film-forming agents, via the solvent casting technique. Hydroxypropyl methylcellulose (HPMC) K100 LV was incorporated as an adjuvant to achieve controlled release. At optimal concentrations (3% w/w starch, 2% w/w chitosan, and 2% w/w HPMC), the films exhibited favorable mechanical properties, swelling capacity, and unfolding behavior. Sustained release of FA over 8 h was achieved in formulations containing HPMC with either Hom-Nil or glutinous rice starch. Among the tested formulations (R6, G6, and H6), those incorporating Hom-Nil rice starch demonstrated the most significant antioxidant (10.38 ± 0.23 μg/mL) and anti-inflammatory (9.26 ± 0.14 μg/mL) effects in murine macrophage cell line (RAW 264.7), surpassing the activities of both free FA and FA-SD. These results highlight the potential of anthocyanin-rich pigmented rice starch-based expandable films as effective gastroretentive systems for enhanced FA delivery Full article

(This article belongs to the Special Issue Natural Polymeric Materials: Polysaccharides and Carbohydrate Polymers, 2nd Edition)

19 pages, 19785 KB

Open AccessArticle

Generation of Randomly Inclined Fibers in the Representative Volume Element for Predicting the Elastic Modulus of Fiber-Reinforced Polymer Composites

by Menglong Shao and Songling Xue

Polymers 2025, 17(17), 2300; https://doi.org/10.3390/polym17172300 - 25 Aug 2025

Abstract

The representative volume element (RVE) is frequently used to forecast the mechanical properties of composites, where the distribution of fibers plays a significant role. This paper proposes a new RVE modeling method for unidirectional fiber-reinforced polymer (UD-FRP) composites, which takes into account the [...] Read more.

The representative volume element (RVE) is frequently used to forecast the mechanical properties of composites, where the distribution of fibers plays a significant role. This paper proposes a new RVE modeling method for unidirectional fiber-reinforced polymer (UD-FRP) composites, which takes into account the random distribution of fiber positions and inclinations. The fiber inclination in the RVE is normally or uniformly distributed. The suggested RVE model was validated using static tests and the fiber structure observed by micro-computed tomography (CT). The effects of fiber volume fraction and maximum fiber inclination on the elastic properties were investigated based on the proposed RVE model. The results indicate that the prediction of transverse properties is considerably impacted by fiber inclination in RVE, with uniformly distributed inclination having a more significant influence than normally distributed inclination. For the transverse Young’s modulus of UD-FRP, the predicted results of the proposed model and the models in the literature differed from the experimental results by 0.30% and 11.45%, respectively. For the in-plane shear modulus of UD-FRP, the predicted results of the proposed model and the models in the literature differed from the experimental results by 1.65% and 8.44%, respectively. Moreover, the fiber volume fraction has a significant effect on the elastic properties, and the maximum inclination of the fibers has a significant effect on the elastic properties except for the longitudinal Poisson’s ratio. The proposed RVE model in this paper can predict the elastic properties of composites more accurately. Full article

(This article belongs to the Special Issue Mechanical Behavior of Polymer Composites)

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17 pages, 1917 KB

Open AccessReview

Next-Generation Food Packaging: Progress and Challenges of Biopolymer-Based Materials

by Raja Venkatesan, Maher M. Alrashed, Alexandre A. Vetcher and Seong-Cheol Kim

Polymers 2025, 17(17), 2299; https://doi.org/10.3390/polym17172299 - 25 Aug 2025

Abstract

Biopolymer-based packaging is emerging as a sustainable replacement for conventional plastic materials. Significant challenges like scalability, machinability, and mechanical properties are preventing biopolymers from industrially advancing despite their sustainable advantages. Also, the usage of materials in packaging is limited due to their toxicity, [...] Read more.

Biopolymer-based packaging is emerging as a sustainable replacement for conventional plastic materials. Significant challenges like scalability, machinability, and mechanical properties are preventing biopolymers from industrially advancing despite their sustainable advantages. Also, the usage of materials in packaging is limited due to their toxicity, the degradation products, and their migration properties. Nanocomposite materials and active packaging methods with the antimicrobial agents showed novel advances with enhanced performance. However, these advances frequently increase the complexity and cost of production. For an assessment of their safe and efficient usage, knowledge gaps on the effects of biopolymer migration and degradation on the environment and human health should be addressed. These challenges, which involve enhanced material characteristics, reducing costs, and aligning regulations, demand interdisciplinary methods. This review explores the prospects for sustainable innovation in packaging by examining the challenges and potential solutions associated with the development of biopolymer-based materials. Full article

(This article belongs to the Special Issue Antimicrobial Food Packaging with Biodegradable Polymers: Preparation, Characterization and Applications)

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24 pages, 8420 KB

Open AccessArticle

Energy Landscape-Guided Virtual Screening of Side-Chain Engineering in Polymer Dynamics Design

by Han Liu, Sen Meng and Liantang Li

Polymers 2025, 17(17), 2298; https://doi.org/10.3390/polym17172298 - 25 Aug 2025

Abstract

Side-chain engineering is versatile for tuning the chain mobility of graft polymers and governs their thermal stability. However, it remains elusive to predict the graft effect on chain mobility, especially for competitive side-chain types. Here, relying on molecular dynamics simulation and energy landscape [...] Read more.

Side-chain engineering is versatile for tuning the chain mobility of graft polymers and governs their thermal stability. However, it remains elusive to predict the graft effect on chain mobility, especially for competitive side-chain types. Here, relying on molecular dynamics simulation and energy landscape theory, we introduce a three-stage virtual pipeline to sequentially refine the screening of graft chain mobility while minimizing computation cost, by taking the example of grafting similar side-chain types (hydroxyethyl methacrylate (HEMA), methyl methacrylate (MMA), and vinyl acetate (VAC)) onto amorphous polypropylene (PP). Ascribed to their structural similarity, these graft systems exhibit a non-evident chain mobility distinction, with the atom displacement—governing the local “roughness” in potential energy landscape (PEL)—exhibiting only weak-to-modest correlation with their initial atomic energy, volume, and stress. This necessitates the subsequent-stage screening for broader PEL navigation, which confirms a stability and roughness rank of VAC ≥ MMA > HEMA > PP, with their chain activation energy revealing that these side chains enhance the PEL roughness through a counterbalance between possibly lowering the overall energy barrier but extensively wrinkling the landscape. Overall, the three-stage screening establishes a state-of-the-art efficient strategy to evaluate thermal stability of graft polymers in stepwise higher precision from local to ergodic roughness inspection. Full article

(This article belongs to the Special Issue Simulation and Calculation of Polymer Composite Materials—2nd Edition)

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17 pages, 2754 KB

Open AccessArticle

Effect of Relaxation Properties on the Bonding Durability of Polyisobutylene Pressure-Sensitive Adhesives

by Anna V. Vlasova, Nina M. Smirnova, Viktoria Y. Melekhina, Sergey V. Antonov and Sergey O. Ilyin

Polymers 2025, 17(17), 2297; https://doi.org/10.3390/polym17172297 - 25 Aug 2025

Abstract

Pressure-sensitive adhesion arises at a specific rheological behavior of polymer systems, which should correlate with their relaxation properties, making them potentially useful for predicting and altering adhesive performance. This work systematically studied the rheology of eco-friendly pressure-sensitive adhesives based on non-crosslinked polyisobutylene ternary [...] Read more.

Pressure-sensitive adhesion arises at a specific rheological behavior of polymer systems, which should correlate with their relaxation properties, making them potentially useful for predicting and altering adhesive performance. This work systematically studied the rheology of eco-friendly pressure-sensitive adhesives based on non-crosslinked polyisobutylene ternary blends free of solvents and byproducts, which serve for reversible adhesive bonding. The ratio between individual polymer components differing in molecular weight affected the rheological, relaxation, and adhesion properties of the constituted adhesive blends, allowing for their tuning. The viscosity and viscoelasticity of the adhesives were studied using rotational rheometry, while their adhesive bonds with steel were examined by probe tack and shear lap tests at different temperatures. The adhesive bond durability at shear and pull-off detachments depended on the adhesive composition, temperature, and contact time under pressure. The double differentiation of the continuous relaxation spectra of the adhesives enabled the accurate determination of their characteristic relaxation times, which controlled the durability of the adhesive bonds. A universal linear correlation between the reduced failure time of adhesive bonds and their reduced formation time enabled the prediction of their durability with high precision (Pearson correlation coefficient = 0.958, p-value < 0.001) over at least a four-order-of-magnitude time range. The reduction in the formation/failure times of adhesive bonds was most accurately achieved using the longest relaxation time of the adhesives, associated with their highest-molecular-weight polyisobutylene component. Thus, the highest-molecular-weight polymer played a dominant role in adhesive performance, determining both the stress relaxation during the formation of adhesive bonds and their durability under applied load. In turn, this finding enables the prediction and improvement of adhesive bond durability by increasing the bond formation time (a durability rise by up to 10–100 times) and extending the adhesive’s longest relaxation time through elevating the molecular weight or proportion of its highest-molecular-weight component (a durability rise by 100–350%). Full article

(This article belongs to the Special Issue Polymer-Based Adhesives: Preparation, Characterization and Applications)

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20 pages, 4388 KB

Open AccessArticle

Investigation of Cryogenic Mechanical Performance of Epoxy Resin and Carbon Fibre-Reinforced Polymer Composites for Cryo-Compressed Hydrogen Storage Onboard Gas Vessels

by Liangliang Qi, Keqing Wang, Zhoutian Ge, Zhuangzhuang Cao, Peiyu Hu, Yuhang He, Sohail Yasin and Jianfeng Shi

Polymers 2025, 17(17), 2296; https://doi.org/10.3390/polym17172296 - 25 Aug 2025

Abstract

To address the brittle matrix failure frequently observed in filament-wound composite layers of onboard pressure vessels operating under cryogenic and high-pressure conditions, we studied a bisphenol-A epoxy resin (DGEBA) system modified with polyetheramine (T5000) and 3,4-Epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate (CY179). The curing and rheological behavior [...] Read more.

To address the brittle matrix failure frequently observed in filament-wound composite layers of onboard pressure vessels operating under cryogenic and high-pressure conditions, we studied a bisphenol-A epoxy resin (DGEBA) system modified with polyetheramine (T5000) and 3,4-Epoxycyclohexylmethyl 3′,4′-epoxycyclohexanecarboxylate (CY179). The curing and rheological behavior of the modified resin were first evaluated, revealing a favorable processing, with viscosity suitable for wet-filament winding. Subsequently, its coefficient of thermal expansion (CTE) and tensile properties were characterized over the 300 K–90 K range, demonstrating a linear increase in elastic modulus and tensile strength with decreasing temperature. Carbon fibre-reinforced polymer composites (CFRP) were then fabricated using this resin system, and both longitudinal and transverse tensile tests, along with microscopic fracture surface analyses, were conducted. The results showed that CFRP-0° specimens exhibited an initial increase followed by a decrease in elastic modulus with decreasing temperature, whereas CFRP-90° specimens demonstrated pronounced cryogenic strengthening, with tensile strength and modulus enhanced by 52.2% and 82.4%, respectively. The findings provide comprehensive properties for the studied resin system and its CFRP under room temperature (RT) to cryogenic conditions, offering a basis for the design and engineering of cryo-compressed hydrogen storage vessels. Full article

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

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18 pages, 2756 KB

Open AccessArticle

Triboelectric-Enhanced Piezoelectric Nanogenerator with Pressure-Processed Multi-Electrospun Fiber-Based Polymeric Layer for Wearable and Flexible Electronics

by Inkyum Kim, Jonghyeon Yun, Geunchul Kim and Daewon Kim

Polymers 2025, 17(17), 2295; https://doi.org/10.3390/polym17172295 - 25 Aug 2025

Abstract

A triboelectricity-enhanced piezoelectric nanogenerator (PENG) based on pressure-processed multi-electrospun polymeric layers is herein developed for efficient vibrational energy harvesting. The hybridization of piezoelectric and triboelectric mechanisms through electrospinning has been utilized to enhance electrical output by increasing contact areas and promoting alignment within [...] Read more.

A triboelectricity-enhanced piezoelectric nanogenerator (PENG) based on pressure-processed multi-electrospun polymeric layers is herein developed for efficient vibrational energy harvesting. The hybridization of piezoelectric and triboelectric mechanisms through electrospinning has been utilized to enhance electrical output by increasing contact areas and promoting alignment within piezoelectric materials. A multi-layer structure comprising alternating poly (vinylidene fluoride) (PVDF) and poly (hexamethylene adipamide) (PA 6/6) exhibits superior electrical performance. A lateral Janus configuration, providing distinct positive and negative triboelectric polarities, has further optimized device efficiency. This approach introduces a novel operational mechanism, enabling superior performance compared to conventional methods. The fiber-based architecture ensures exceptional flexibility, low weight, and a high surface-to-volume ratio, enabling enhanced energy harvesting. Experimentally, the PENG achieved an open-circuit voltage of 14.59 V, a short-circuit current of 205.7 nA, and a power density of 7.5 mW m⁻² at a resistance of 30 MΩ with a five-layer structure subjected to post-processing under pressure. A theoretical model has mathematically elucidated the output results. Long-term durability (over 345,600 cycles) has confirmed its robustness. Demonstrations of practical applications include monitoring human joint motion and respiratory activity. These results highlight the potential of the proposed triboelectricity-enhanced PENG for vibrational energy harvesting in flexible and wearable electronic systems. Full article

(This article belongs to the Special Issue Advances in Polymer Composites for Nanogenerator Applications)

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11 pages, 2639 KB

Open AccessArticle

Trap Engineering-Based Optimization via Polyetherimide with Molecular Semiconductor for Capacitive Energy Storage at High Temperatures

by Dingqu Liu, Hao Chen, Lihe Guo, Hongfei Li and Haiping Xu

Polymers 2025, 17(17), 2294; https://doi.org/10.3390/polym17172294 - 25 Aug 2025

Abstract

Polyetherimide (PEI)/molecular semiconductor-based all-organic dielectric composites have garnered significant attention due to their exceptional energy storage performance at elevated temperatures. In this work, the high-electron-affinity semiconductor 5,6,12,13-tetrachloro-2,9-bis(2-ethylhexyl)anthra[2,1,9-def:6,5,10-d′e′f]diisoquinoline-1,3,8,10(2H,9H)-tetraone (TCEHAQ) is employed as a filler to enhance the dielectric energy storage performance of PEI. It [...] Read more.

Polyetherimide (PEI)/molecular semiconductor-based all-organic dielectric composites have garnered significant attention due to their exceptional energy storage performance at elevated temperatures. In this work, the high-electron-affinity semiconductor 5,6,12,13-tetrachloro-2,9-bis(2-ethylhexyl)anthra[2,1,9-def:6,5,10-d′e′f]diisoquinoline-1,3,8,10(2H,9H)-tetraone (TCEHAQ) is employed as a filler to enhance the dielectric energy storage performance of PEI. It is believed that TCEHAQ can immobilize electrons and reduce charge transport in dielectric composites. The results demonstrate that the breakdown strength of PEI with only 0.5 wt% of TCEHAQ increased from 450 MV/m to 600 MV/m at room temperature, while the maximum discharge energy density (U_d) reached 5.99 J/cm³, and the discharge efficiency (η) was 96.5%. Meanwhile, the breakdown strength of the 0.5 wt% TCEHAQ/PEI blend at 150 °C was 500 MV/m, and the maximum U_d and η were 3.68 J/cm³ and 81.0%, respectively. This is a straightforward and effective method for fabricating large-area, high-quality dielectric energy storage films suitable for use in harsh environments. Full article

(This article belongs to the Section Polymer Applications)

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11 pages, 6411 KB

Open AccessArticle

Silicified Wood with Dual Fire Retardancy and Thermal Management Functionalities

by Kunkun Tu, Jinjing Liu, Jiayi Li, Suhao Li, Xu Zhang and Shihang Li

Polymers 2025, 17(17), 2293; https://doi.org/10.3390/polym17172293 - 25 Aug 2025

Abstract

Fire retardancy and thermal management are critical for energy-efficient, fire-safe buildings. Natural wood, a mainstream construction material, possesses inherent advantages but lacks such dual functionality. Silicified wood was fabricated via multi-cycle silicification of native wood, where SiO₂ uniformly infiltrates and fills the [...] Read more.

Fire retardancy and thermal management are critical for energy-efficient, fire-safe buildings. Natural wood, a mainstream construction material, possesses inherent advantages but lacks such dual functionality. Silicified wood was fabricated via multi-cycle silicification of native wood, where SiO₂ uniformly infiltrates and fills the lumens. The treated wood material displays an improved limiting oxygen index (LOI) from 21.9% to 36.0%, and delayed ignition from 15 s to 50 s, compared to untreated wood. It demonstrates a low thermal conductivity of 0.074 W·m⁻¹·K⁻¹, showing enhanced emissivity. When heated on a 75 °C hot plate, the silicified wood surface reaches ~50 °C after 5 s, versus ~60 °C for native wood. These enhancements collectively improve thermal management performance, achieving insulation through reduced thermal conduction and passive cooling via optimized infrared regulation. Ultimate tensile stress remains nearly unchanged post-treatment, while toughness is significantly improved. This work advances wood as a sustainable building material, with promising potential for fire-safe, energy-efficient construction applications. Full article

(This article belongs to the Special Issue Eco-Friendly Supramolecular Polymeric Materials, 2nd Edition)

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21 pages, 1944 KB

Open AccessArticle

Principles and Practical Steps of Simplifying the Construction of the Cushion Curves of Closed-Cell Foam Materials

by Deqiang Sun, Pengcheng Qiu, Hongjuan Chen, Xinyuan Zhang and Siyu Wang

Polymers 2025, 17(17), 2292; https://doi.org/10.3390/polym17172292 - 24 Aug 2025

Abstract

The cushion curves of cushioning materials play crucial roles in scientific and reliable cushioning designs and in reducing damage losses for fragile products during distributions. The construction methods of cushion curves of closed-cell foam materials (CFMs) mainly include the Janssen factor, Rusch curve, [...] Read more.

The cushion curves of cushioning materials play crucial roles in scientific and reliable cushioning designs and in reducing damage losses for fragile products during distributions. The construction methods of cushion curves of closed-cell foam materials (CFMs) mainly include the Janssen factor, Rusch curve, cushion factor, and energy absorption diagram. The construction principle of these methods is reviewed in detail, and their disadvantages are mainly discussed. According to relevant ASTM and GB/T experimental standards, the peak acceleration–static stress cushion curve is based on dynamic impacts, which are most consistent with the dropping situation of product packages, so this kind of cushion curve is the standard and most widely applied for product cushioning designs. However, when generating the peak acceleration–static stress cushion curves, the experimental work is extremely huge. Three methods, namely the dynamic factor method, dynamic stress–dynamic energy method, and dynamic cushion factor–dynamic energy method, can significantly reduce the experimental workload and simplify constructing cushion curves. The novel dynamic cushion factor–dynamic stress method is proposed to simplify constructing the cushion curves. The practical generation steps of constructing cushion curves based on the four simplified methods are created and presented in detail. Full article

(This article belongs to the Special Issue Advances in Cellular Polymeric Materials)

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