Polymers

20 pages, 10689 KB

Open AccessArticle

Selective Elastane Removal Using DMSO–DBN Under Moderate Temperatures: From Pure Filaments to Cotton/Polyester Blends

by Tiago Azevedo, Ana Catarina Silva, Diego M. Chaves, Raul Fangueiro and Diana P. Ferreira

Polymers 2025, 17(24), 3247; https://doi.org/10.3390/polym17243247 (registering DOI) - 6 Dec 2025

Selective removal of elastane from textile blends is a critical factor for fibre-to-fibre recycling, since even low elastane content compromises the mechanical shredding efficiency, contaminates recycled streams, and limits the spinnability of recovered fibres. In this work, we investigate dimethyl sulfoxide (DMSO) as [...] Read more.

Selective removal of elastane from textile blends is a critical factor for fibre-to-fibre recycling, since even low elastane content compromises the mechanical shredding efficiency, contaminates recycled streams, and limits the spinnability of recovered fibres. In this work, we investigate dimethyl sulfoxide (DMSO) as a solvent system for elastane degradation under moderate temperatures, both in the absence and in the presence of the organic base catalyst 1,5-diazabicyclo[4.3.0]non-5-ene (DBN). DMSO alone promoted only partial elastane mass loss, typically 26–32% at 80–100 °C (60 min) and up to 79% at 120 °C (10 min), whereas the addition of 0.1% v/v DBN enabled near-complete or complete mass loss (81–100%) across 80–120 °C within 10–60 min. Complete removal of elastane was achieved in isolated elastane filaments at 100 °C within 30–60 min, and the same treatment conditions were applied to real mixtures of pre-consumer textile waste containing 94% cotton/6% elastane and 87% polyester/13% elastane, leading to permanent dimensional relaxation of the resulting fabrics with area increases of approximately 9–14% and 7–13%, respectively, consistent with the loss of elastane-driven elastic recovery. Scanning electron microscopy (SEM), tensile testing, and dimensional analysis confirmed selective disruption of the elastane, a loss of elastic recovery, and largely preserved morphology and tensile strength of the cotton and polyester fibres. Dimensional change in the treated fabrics served as an indirect indicator of elastane degradation, correlating with the loss of elasticity observed in both blends. In summary, the DMSO–DBN system provides an energy-efficient, controllable, and scalable route for elastane degradation under comparatively mild conditions, thereby contributing to fibre-to-fibre recycling strategies and the advancement of circular textile manufacturing. Full article

(This article belongs to the Special Issue Advanced Study on Polymer-Based Textiles)

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12 pages, 2401 KB

Open AccessArticle

Kinetic Analysis and Products Characterization of Hydrothermal Liquefaction of Tetra Pak Waste for Bio-Oil Production

by Yuzhen Wang, Ao Lu, Zhuan Liu, Yu Feng, Di Shan and Changqing Fang

Polymers 2025, 17(24), 3246; https://doi.org/10.3390/polym17243246 - 5 Dec 2025

Abstract

Hydrothermal liquefaction (HTL) of Tetra Pak waste was investigated at 320–440 °C for 10–50 min to produce bio-crude oil. Bio-oil yield increased with temperature and time, reaching about 43 wt% at 40–50 min, while solid residue decreased and stabilized. Boiling point analysis indicated [...] Read more.

Hydrothermal liquefaction (HTL) of Tetra Pak waste was investigated at 320–440 °C for 10–50 min to produce bio-crude oil. Bio-oil yield increased with temperature and time, reaching about 43 wt% at 40–50 min, while solid residue decreased and stabilized. Boiling point analysis indicated diesel- and kerosene-range fractions as dominant components. FT-IR results showed enhanced aromatic and carbonyl groups with reaction time, suggesting secondary condensation. A modified first-order kinetic model described the conversion of carbohydrates and polyethylene, with activation energies of 25.8–49.0 and 54.9–78.3 kJ mol⁻¹, respectively. The intermediate aqueous/gaseous pathway exhibited a lower activation energy (30.1 kJ mol⁻¹), highlighting its vital role in oil formation. This study advances understanding of Tetra Pak liquefaction and provides guidance for efficient composite waste valorization. Full article

(This article belongs to the Special Issue Thermochemical Conversion of Polymer Waste)

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4 pages, 281 KB

Open AccessEditorial

Selected Papers in 2023–2024 in the ‘Polymer Applications’ Section

by Hyeonseok Yoon

Polymers 2025, 17(24), 3245; https://doi.org/10.3390/polym17243245 - 5 Dec 2025

Abstract

During 2023 and 2024, the Section “Polymer Applications” of the MDPI journal Polymers achieved an exceptional level of academic productivity, as evidenced by the publication of 995 peer-reviewed articles and several high-impact Special Issues [...] Full article

(This article belongs to the Section Polymer Applications)

18 pages, 2902 KB

Open AccessArticle

Integrating Polypropylene Fibers and Cement in Clays for Sustainable Clay Bricks

by Muawia Dafalla and Awadh Abden

Polymers 2025, 17(24), 3244; https://doi.org/10.3390/polym17243244 - 5 Dec 2025

Abstract

This study investigates how adding polypropylene fibers and cement affects the strength of highly plastic clay used in clay bricks. The research looked at various curing times to improve the strength of clay bricks for effective use in the construction industry. A fiber [...] Read more.

This study investigates how adding polypropylene fibers and cement affects the strength of highly plastic clay used in clay bricks. The research looked at various curing times to improve the strength of clay bricks for effective use in the construction industry. A fiber content of 0.2% was added to the clay and compared to untreated control samples improved with varied amounts of cement (2%, 4%, and 6%). The influence of curing on strength increase was explored, as well as the profile of the stress–strain relationship. The compressive strength increased by 53% to 140% after 7 days of curing, which is almost a quarter of the strength attained after 28 days. The results showed a considerable increase in strength, illustrating the cumulative benefits of longer curing times and the suggested additions. Fiber addition was shown to be associated with a significant increase in compressive strength. This advantage is due to the particle connection established by incorporating the fibers and cement into the mixture. Improvement in tensile and shear strength was investigated. It was also found that fibers made the material more ductile. It was noted that using cement alone can increase the compressive strength but cracking and shrinkage control may not be achieved. When compared to the untreated sample, mixtures containing 0.2% fibers and treated with 2%, 4%, and 6% cement increased compressive strength by 225%, 390%, and 630%, respectively. This improvement is comparable to a 2-, 4-, or 6-fold improvement. This increase will enhance the supporting capacity of the non-load-bearing clay bricks. Full article

(This article belongs to the Special Issue Sustainable Polymeric Materials in Building and Construction, 2nd Edition)

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17 pages, 814 KB

Open AccessArticle

A Method for Mitigating Degradation Effects on Polyamide Textile Yarn During Mechanical Recycling

by Petra Drohsler, Martina Pummerova, Dominika Hanusova, Daniel Sanetrnik, Dagmar Foldynova, Jan Marek, Lenka Martinkova and Vladimir Sedlarik

Polymers 2025, 17(24), 3243; https://doi.org/10.3390/polym17243243 - 5 Dec 2025

Abstract

The phenomenon of fast fashion has resulted in high yarn consumption and growing textile waste from both manufacturing and consumers. Rising environmental awareness and evolving legislation, including landfill restrictions, have prompted the search for sustainable recycling methods to manage textile end-of-life. This study [...] Read more.

The phenomenon of fast fashion has resulted in high yarn consumption and growing textile waste from both manufacturing and consumers. Rising environmental awareness and evolving legislation, including landfill restrictions, have prompted the search for sustainable recycling methods to manage textile end-of-life. This study investigates the mechanical recycling of polyamide 6.6 (PA66) yarn using a chain extender (Joncryl) and antioxidant (Irganox). Thermogravimetric analysis (TGA) confirmed that thermal stability in recycled PA66 was maintained compared to the original yarn, and the presence of Joncryl further enhanced this stability. Oxidative-onset temperature (OOT), measured by differential scanning calorimetry (DSC), supported these improvements. Gas chromatography–mass spectrometry (GC/MS) identified key degradation products, which were correlated with changes in the polymer matrix. Mechanical testing showed a 31% decrease in Young’s modulus after initial recycling, which was reversed with further processing. This behavior suggests the formation of shortened semi-crystalline chains and new linkages promoted by Joncryl. Viscosity and limiting viscosity number increased by up to 50%, depending on both additive concentrations. Overall, Joncryl and Irganox enhanced viscosity, mechanical strength, and notably thermal stability, confirming their suitability for recyclable textile-grade PA66 yarns. Full article

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

17 pages, 2077 KB

Open AccessArticle

Carbon Footprint of Plastic Bags and Polystyrene Dishes vs. Starch-Based Biodegradable Packaging in Amazonian Settlements

by Johanna Garavito, Néstor C. Posada, Clara P. Peña-Venegas and Diego A. Castellanos

Polymers 2025, 17(24), 3242; https://doi.org/10.3390/polym17243242 - 5 Dec 2025

Abstract

C footprint is a feature used to search the integral life cycle of a product to predict its environmental impact. The packaging industry is changing rapidly to the production of biodegradable products to mitigate the negative environmental consequences of the use of single-use [...] Read more.

C footprint is a feature used to search the integral life cycle of a product to predict its environmental impact. The packaging industry is changing rapidly to the production of biodegradable products to mitigate the negative environmental consequences of the use of single-use packages. It is thought that biodegradable packages should be more sustainable than traditional plastics due to the sources of the raw materials used to produce them, but this is not always true and depends on the issues considered, the methodology, and the scale analyzed. Limited research includes case studies from developing countries where waste management is less efficient and where the environmental impacts of single-use packaging can be more significant. This paper evaluates the C footprint of bags and dishes made from traditional or local biodegradable sources in an Amazonian settlement of Colombia, such as thermoplastic cassava starch and powdered plantain leaves, to evaluate the impact of locally made biodegradable packaging vs. imported petrochemical ones. Results show that using local raw materials and in situ production reduces the C footprint of biodegradable packages, considering that the energy source for production and transport are important contributors to the C footprint beyond the raw materials used, with ratios that can be between 0.1 and 7 times more kg CO₂ eq generated per functional unit. Full article

(This article belongs to the Special Issue Applications of Biopolymer-Based Composites in Food Technology)

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18 pages, 8979 KB

Open AccessArticle

Mechanical Behavior of Carbon-Fiber-Reinforced Polymer Composites (Towpreg) Under Various Temperature Conditions

by Yoonduck Seo, Jiming Sun, Amit Dixit, Da Hye Kim, Yuen Xia and Sung Kyu Ha

Polymers 2025, 17(24), 3241; https://doi.org/10.3390/polym17243241 - 5 Dec 2025

Abstract

As the hydrogen economy rapidly expands, carbon-fiber-reinforced polymer composites (Towpreg) have become key materials for next-generation hydrogen pressure vessels, offering superior processability, reproducibility, and storage stability compared to conventional wet-winding composites. Since hydrogen storage vessels are evaluated at three representative service temperatures (−40, [...] Read more.

As the hydrogen economy rapidly expands, carbon-fiber-reinforced polymer composites (Towpreg) have become key materials for next-generation hydrogen pressure vessels, offering superior processability, reproducibility, and storage stability compared to conventional wet-winding composites. Since hydrogen storage vessels are evaluated at three representative service temperatures (−40, 25, and 85 °C), Towpreg materials must maintain consistent mechanical performance across this range to meet certification standards. This study establishes an integrated methodology combining Towpreg panel fabrication, temperature-controlled tensile and fatigue testing, and quantitative assessment of thermo-mechanical stability using DM epoxy resin as the matrix. To address artifacts such as tab slippage at high temperatures and inefficiency at low temperatures, a “Localized Thermal Control” approach was developed. The HY-Mini Heater System enables localized heating at 85 °C, while the HY-Cooler System applies a Joule–Thomson-based Stirling cooler for efficient localized cooling at −40 °C. Quantitative evaluation showed tensile strengths of 2973.3 MPa (RT), 2767.3 MPa (HT, ~7% decrease), and 2907.7 MPa (LT, ~2% decrease). Under R = 0.1 fatigue testing, the Basquin slope (m) was 11.97 (RT), 9.98 (HT), and 10.6 (LT), while the intercept (log b ≈ 3.7) remained nearly constant. These results confirm the excellent thermo-mechanical stability of the carbon-fiber-reinforced polymer composites (Towpreg) for hydrogen tank applications. Full article

(This article belongs to the Special Issue Fiber Reinforced Polymeric Composites)

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19 pages, 3444 KB

Open AccessArticle

Effect of PBAT-g-MAH Compatibilization and Bamboo Flour Loadings on Melt Flow and Early Soil–Compost Mineralization of PLA Biocomposites for FFF 3D Printing

by César A. Paltán, Jorge I. Fajardo, Diana V. Rodriguez and Edwuin Carrasquero

Polymers 2025, 17(24), 3240; https://doi.org/10.3390/polym17243240 - 5 Dec 2025

Abstract

Objective. To determine how bamboo loadings (2.5–5 wt%) and compatibilization with PBAT-g-MAH (BP-1, 10 wt%) affect melt flow and early-time mineralization of PLA biocomposites under near-ambient soil–compost conditions (ASTM D5988), while using PBAT-g-GMA (BP-2) only as a melt-flow screening reference. Methods. Melt flow [...] Read more.

Objective. To determine how bamboo loadings (2.5–5 wt%) and compatibilization with PBAT-g-MAH (BP-1, 10 wt%) affect melt flow and early-time mineralization of PLA biocomposites under near-ambient soil–compost conditions (ASTM D5988), while using PBAT-g-GMA (BP-2) only as a melt-flow screening reference. Methods. Melt flow index (MFI, ASTM D1238, 2.16 kg; 190/210/230 °C) was first measured for neat PLA and PLA/BP-1/BP-2 blends to select a printable matrix. PLA/10BP-1 composites containing 2.5–5 wt% bamboo were then compounded, extruded as bars for biodegradation tests, and validated by FFF printing. Biodegradation was quantified from titrimetric CO₂ evolution in soil–compost reactors at 21 ± 2 °C and pH ≈ 7 (triplicate specimens plus triplicate blanks; mean ± SD and endpoint statistics). ATR-FTIR was used to support mechanistic interpretation. Results. BP-1 markedly increased MFI relative to neat PLA, whereas BP-2 remained close to the neat matrix, consistent with epoxy-driven coupling that can raise viscosity. Under ambient burial, all materials exhibited very low mineralization over 0–23 days; PLA/10BP-1/2.5B and PLA/10BP-1/5B showed a slight increase in net CO₂ evolution compared with neat PLA, but the differences remained modest and within the experimental uncertainty, reflecting a balance between bamboo’s pro-hydrolytic effect and the sealing action of PBAT-g-MAH compatibilization. Significance. The data delineate a printing–degradation window in which PLA/10BP-1 with 2.5–5 wt% bamboo combines easy processing and short-term durability while preserving industrial compostability at end-of-life. Full article

(This article belongs to the Special Issue Mechanical Properties of 3D Printed Polymer Composites)

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17 pages, 2859 KB

Open AccessArticle

Investigation of Processing Conditions and Product Geometry in Out-Mold Decoration and Their Effects on Film Adhesion and Deformation

by Hui-Li Chen, Po-Wei Huang, Sheng-Hsun Hsu and Jhong-Sian Wu

Polymers 2025, 17(24), 3239; https://doi.org/10.3390/polym17243239 - 5 Dec 2025

Abstract

The growing demand for high-quality decorative polymer surfaces has increased interest in Out Mold Decoration (OMD), yet the combined influence of processing conditions and product geometry on film adhesion and deformation remains insufficiently defined. This study establishes an integrated framework that connects OMD [...] Read more.

The growing demand for high-quality decorative polymer surfaces has increased interest in Out Mold Decoration (OMD), yet the combined influence of processing conditions and product geometry on film adhesion and deformation remains insufficiently defined. This study establishes an integrated framework that connects OMD process parameters with geometry-dependent deformation behavior using polycarbonate films printed with an ink grid. Adhesion and surface quality were evaluated using 2.5D specimens, while 3D models with varied fillet radii, slopes, and heights enabled quantitative assessment of grid-spacing evolution and thickness distribution. Results show that preheating smooths the film without improving adhesion, whereas increasing the forming environment temperature enhances both bonding and surface quality within the material’s thermal tolerance. Vacuum pressure strengthens film–substrate contact but requires moderation to prevent overstretching. An optimized condition of 100 °C preheating, 90 °C forming temperature, and 2.5 kg vacuum pressure provides a balanced performance. Geometric factors exert strong control over deformation, with small radii, steep slopes, and tall features producing greater strain and nonuniform thinning. These findings establish practical processing windows and geometry guidelines for achieving reliable OMD components that integrate high visual quality with stable adhesion performance. Full article

(This article belongs to the Special Issue Advances in Polymer Processing Technologies: Injection Molding)

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16 pages, 3369 KB

Open AccessArticle

Temperature Dependence of Tensile Properties and Deformation Behavior in Highly Strong Heat-Elongated Polypropylene

by Karin Onaka and Hiromu Saito

Polymers 2025, 17(24), 3238; https://doi.org/10.3390/polym17243238 - 5 Dec 2025

Abstract

We investigated the tensile properties and deformation behavior at various temperatures of highly strong heat-elongated polypropylene (PP), in which stacks of crystalline lamellae are macroscopically arranged in the elongated direction and lamellae are connected by thin fibrils. The elastic modulus E′ and [...] Read more.

We investigated the tensile properties and deformation behavior at various temperatures of highly strong heat-elongated polypropylene (PP), in which stacks of crystalline lamellae are macroscopically arranged in the elongated direction and lamellae are connected by thin fibrils. The elastic modulus E′ and the αc-relaxation temperature for the onset of crystalline chain motion, obtained through dynamic mechanical analysis, were higher in the heat-elongated than the unelongated PP, indicating the suppression of crystalline chain motion. The heat-elongated PP deformed beyond the yield point at high temperatures above the αc-relaxation point, and it exhibited high tensile stress; e.g., the yield stress was 60 MPa at 120 °C, which was 7.5 times higher than that of the unelongated PP. Small-angle X-ray scattering intensity patterns changed from layered to diffuse, and DSC thermograms showed that melting peak position shifted to lower temperatures when stretching at small strains at various temperatures. The results suggest that lamella fragmentation occurs under small strains at various temperatures. Thus, the good high-temperature strength of the heat-elongated PP is due to the fragmentation of lamellae during small-strain stretching and the suppression of crystalline chain motion by thin crystalline fibrils connected to the lamellae. Full article

(This article belongs to the Special Issue Mechanical Properties and Thermal Analysis of Polymer Materials)

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19 pages, 17044 KB

Open AccessArticle

Molecular Dynamics Simulations of NXT-Modified Silica Dispersion Mechanism in Natural Rubber

by Chunmei Lv, Fei Niu, Rongfeng Jiang, Yuan Hu, Lu Liu and Xiaolai Zhang

Polymers 2025, 17(24), 3237; https://doi.org/10.3390/polym17243237 - 5 Dec 2025

Abstract

To tackle the critical challenges of silica dispersion and interfacial compatibility in natural rubber composites, this study investigated the dispersion behavior of 3-Octanoylthio-1-propyltriethoxysilane (NXT)-modified silica in natural rubber (NR) and the mechanism by which it affects mechanical properties. Three distinct models were constructed: [...] Read more.

To tackle the critical challenges of silica dispersion and interfacial compatibility in natural rubber composites, this study investigated the dispersion behavior of 3-Octanoylthio-1-propyltriethoxysilane (NXT)-modified silica in natural rubber (NR) and the mechanism by which it affects mechanical properties. Three distinct models were constructed: an NR model, an NR composite model containing unmodified silica (SiO₂), and an NR composite model containing NXT-modified silica (NXT-SiO₂). The radial distribution function (RDF) was used to characterize the dispersion of fillers. The results of filler–filler interactions revealed a reduction in the number of hydrogen bonds between NXT-SiO₂ fillers, weakening the filler network strength and enabling NXT-SiO₂ to exhibit excellent dispersion. The results of filler–rubber interactions indicated that NXT-SiO₂ exhibited stronger interaction forces and compatibility with natural rubber compared to SiO₂. To verify the effect of NXT-SiO₂ on the mechanical properties of natural rubber composites, uniaxial tensile deformation via molecular dynamics simulation was performed on the three models. The simulation results show that the addition of NXT-SiO₂ significantly increases the tensile strength and fracture strain of the composite material, markedly enhancing its mechanical properties. Further studies indicate that NXT-SiO₂ improves the overall mechanical properties of the material by altering the distribution of local natural rubber chains. This work elucidated the intrinsic mechanisms—on a molecular level—by which NXT silane coupling agent modifications enhance the dispersion of fillers and improve the mechanical properties of rubber, thereby providing a theoretical basis for the design of high-performance rubber composites. Full article

(This article belongs to the Section Polymer Networks and Gels)

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Polymers, Volume 17, Issue 24 (December-2 2025) – 11 articles

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