Journal of Applied Polymer Science最新文献

Dynamic covalent polymer networks represent new opportunities in the design of sustainable epoxy resins due to their excellent reprocessability. However, these vitrimers typically exhibit mechanical brittleness and poor resilience performance, limiting their applications in sealing, vibration damping, and impact resistance. E44/poly(2-methyl-1,3-propanediol adipate)/glutaric acid (E44/PMPA/GA) epoxy elastomers, with high resilience, reprocessability, and chemical degradability, were synthesized through epoxy-carboxylic acid opening-ring reactions. The E44/PMPA₂/GA₈ vitrimers exhibited the highest cross-linking density (226.3 mol/m³), a T_g of 22.8°C (from DMA), and high thermal stability (T_i: 337°C). Owing to flexible chains and a moderate cross-linking density, the E44/PMPA₁₀ exhibited superior resilience (residual strain 5.6% after five tensile cycles). Meanwhile, the dynamic ester bonds within the networks endowed the E44/PMPA/GA with self-healing ability and recyclability. In addition, the vitrimers were completely chemically degradable. By regulating the synergistic effects of flexible chain segments and dynamic bonds, this work provided a promising and feasible route for the preparation of epoxy elastomers that integrate high resilience, reprocessability, and chemical degradability.

Poly(methyl methacrylate) (PMMA) possesses high optical transparency but suffers from insufficient mechanical strength. Most toughening methods compromise optical clarity, processability, or industrial scalability. Herein, we present a scalable toughening strategy based on copolymerization of methyl methacrylate (MMA) with 2-hydroxyethyl methacrylate (HEMA), combined with transesterification between their units. The resulting random MMA-co-HEMA copolymers retain excellent visible-light transmittance (above 90.0%, 5 mm) while achieving remarkable mechanical enhancements, including increases of 74% in tensile strength and 22% in impact strength compared with linear PMMA. Further studies reveal that the transesterification between HEMA and MMA units induces a lightly cross-linked network. This approach not only offers advantages in simplicity, cost-effectiveness, and compatibility with industrial processes such as casting molding, but also effectively prevents uncontrollable autoacceleration during bulk polymerization. These findings provide new insights for the designing of high-performance optical thermoplastics with promising potential in structural optical applications.

Fused filament fabrication (FFF) of shape memory polymer composites (SMPCs) offers potential for aerospace applications requiring mechanical robustness and reliable shape-memory performance. However, performance-oriented process optimization remains challenging. Therefore, this study establishes an experiment-driven process-property database and develops a framework to predict tensile strength, shape fixation ratio, and shape recovery ratio. Tensile and thermomechanical data are obtained through full-factorial and orthogonal experiments, and analysis of variance is used to evaluate the effects of the experimental factors on the corresponding properties. On this basis, a data-divide-assisted genetic algorithm-optimized backpropagation neural network (DDGA-BP) is developed. The model retains the trained network and its training record obtained during genetic optimization and uses the retained network for final prediction, thereby improving prediction stability and reproducibility. To evaluate reliability and stability, DDGA-BP is compared with multiple linear regression, random forest regression, and conventional GA-BP over ten repeated carbon-content-stratified data splits. DDGA-BP achieves the highest mean $��R^2�$ values of 0.836, 0.942, and 0.931 for the three properties, together with the lowest mean MAE and RMSE and lower variability than conventional GA-BP. The proposed framework enables accurate and reproducible property prediction and supports performance-oriented design of 4D-printed SMPC components.

The inherent viscoelastic behaviors of dielectric elastomers (DEs), such as creep and hysteresis, are important for their long-term service stability and energy efficiency in cyclic applications. In this work, a constrained interface between dielectric filler and silicone rubber matrix was constructed by modifying nano-silica surface with vinylmethyl dimethoxysilane (VMDMS). By the co-crosslinking reaction among the vinyl groups of modified nano-silica and polymethylvinylsiloxane (PMVS) matrix, the polymer chain mobility was restricted and the filler dispersion was improved. The as-obtained VMDMS@SiO₂/PMVS nanocomposites exhibited remarkably enhanced compressive creep as low as 0.25%, which was 86% lower than that of SiO₂/PMVS nanocomposite. Furthermore, the constrained interface also provided excellent dielectric stability after creep and minimized hysteresis loss during cyclic loading. This study presents an effective interfacial design strategy for developing durable and reliable DEs with suppressed viscoelasticity, which has the potential for applications in soft robotics and energy harvesting.

Glass fiber-reinforced flame-retardant PBT (FR-GF/PBT) is widely used in various insulating, structural, and flame-retardant components for building electrical applications. Many of these components are used in hygrothermal environments. To reduce the performance degradation of FR-GF/PBT under hygrothermal conditions, a series of GF-PBT composites were prepared by melt extrusion using recycled poly(butylene terephthalate) (R-PBT) as the matrix, glass fiber (GF) as the reinforcement, aluminum phosphite (Al-P) as the flame retardant, and Paragonite (Pgt) as the functional additive. The effects of Pgt and Al-P on the flame retardancy, thermal properties, and mechanical properties of the GF-PBT composites were investigated. The results showed that Al-P could effectively improve the flame retardancy of GF-PBT but caused significant reductions in the strength, toughness, and thermal stability of the composite. Al-P and Pgt exhibited a synergistic flame-retardant effect in GF-PBT, and Pgt improved the mechanical and thermal properties of the composites. Pgt could effectively reduce the degradation of flame retardancy and mechanical properties of GF-PBT/Al-P/Pgt composites under hygrothermal environments. This work provides a novel strategy for preparing flame-retardant reinforced PBT building materials with excellent comprehensive properties for applications in hygrothermal environments.

In this paper, the resin films were selected as energy directors, and the influence of flat energy director thickness and welding time on the ultrasonic welding joints of GF-PPS composites was investigated. The ultrasonic welding termination condition was set to time-control mode in order to analyze the influence of energy director thickness on the interface formation. The viscoelastic heat generation and interfacial temperature distribution of energy directors with different thicknesses during the welding process were analyzed using COMSOL software and a thermocouple. The interface and defect formation mechanisms were analyzed by examining the macro and microstructural characterization of the joint cross-section. The lap shear strength of joints under different welding parameters was evaluated through single lap shear tests, while the fracture mechanisms were analyzed using a scanning electron microscope. Furthermore, these findings can be extended to other types of composites, which provide valuable insights for improving the ultrasonic welding process of thermoplastic composites.

Helium and neon are strategically important noble gases in semiconductor manufacturing and cryogenic technologies, yet their similar molecular sizes and inertness make separation challenging. Although membrane-based separation offers an energy-efficient alternative to cryogenic processes, polymer membranes and theoretical designs for He/Ne separation remain limited. In this study, the free volume of polyimides based on 6FDA was tailored by incorporating different diamine structures, and the resulting effects on He/Ne separation performance were systematically investigated. Two classes of diamines were selected: monoaromatic diamines affecting chain symmetry and stacking, and diaromatic bridged diamines introducing varying degrees of chain rigidity. Structure-dependent differences in chain packing and free volume were analyzed using PALS and MD simulations. A quantitative correlation between free volume parameters and gas transport properties established a clear structure–property relationship. Among the studied membranes, 6FDA-ODA polyimide membrane prepared from 6FDA and ODA exhibited a favorable permeability–selectivity balance with helium permeability of 134.78 barrer and an ideal He/Ne selectivity of 6.18. The membrane maintained stable permeation at 200 psi and exhibited increased selectivity after physical aging. These results demonstrate that tuning diamine structures effectively regulates chain packing and free volume, enabling the development of high performance 6FDA-based polyimide membranes for He/Ne separation.

Solar-powered steam generation is acknowledged as a highly efficient method for seawater desalination and wastewater purification. However, simultaneous generation of fresh water and removal of pollutants is still challenging for the treatment of saline wastewater containing organic pollutants. Herein, composite hydrogels with vertically aligned channels were prepared by directional freezing technology. The formation of vertical channels could greatly reduce mass transfer resistance and improve both interfacial evaporation rate and adsorption rate of pollutants. Compared to the non-vertically aligned composite hydrogel, this uniquely structured hydrogel exhibited superior desalination performance, attaining an evaporation rate of 1.99 kg·m⁻²·h⁻¹ and an energy conversion efficiency of 94.36% when exposed to one sun's illumination. Meanwhile, the hydrogel evaporator showed outstanding salt resistance even in the evaporation of brine with high salinity and stable desalination performance over successive evaporation for 10 cycles. In addition, the composite hydrogel was used as an adsorbent for the removal of perfluorooctanoic acid (PFOA). Due to the presence of directional channels, the composite hydrogel achieved higher adsorption capacity and faster adsorption rate than the non-vertically aligned composite hydrogel. This work realized integration of solar desalination and PFOA removal in a single evaporator, offering a facile strategy for treating saline wastewater containing organic pollutants.

Solar-powered steam generation is acknowledged as a highly efficient method for seawater desalination and wastewater purification. However, simultaneous generation of fresh water and removal of pollutants is still challenging for the treatment of saline wastewater containing organic pollutants. Herein, composite hydrogels with vertically aligned channels were prepared by directional freezing technology. The formation of vertical channels could greatly reduce mass transfer resistance and improve both interfacial evaporation rate and adsorption rate of pollutants. Compared to the non-vertically aligned composite hydrogel, this uniquely structured hydrogel exhibited superior desalination performance, attaining an evaporation rate of 1.99 kg·m⁻²·h⁻¹ and an energy conversion efficiency of 94.36% when exposed to one sun's illumination. Meanwhile, the hydrogel evaporator showed outstanding salt resistance even in the evaporation of brine with high salinity and stable desalination performance over successive evaporation for 10 cycles. In addition, the composite hydrogel was used as an adsorbent for the removal of perfluorooctanoic acid (PFOA). Due to the presence of directional channels, the composite hydrogel achieved higher adsorption capacity and faster adsorption rate than the non-vertically aligned composite hydrogel. This work realized integration of solar desalination and PFOA removal in a single evaporator, offering a facile strategy for treating saline wastewater containing organic pollutants.