Journal of Applied Polymer Science最新文献

This study investigates dielectric relaxation and thermal degradation in PS/rutile TiO₂ nanocomposites. Films were fabricated via solution mixing and hot pressing, with 5 wt% loading identified as the optimal concentration for uniform dispersion. Impedance spectroscopy (90°C–150°C) revealed non-Debye Maxwell-Wagner-Sillars (MWS) interfacial polarization, accurately captured by an equivalent circuit model (χ ² ≈ 4.95 × 10⁻⁵). Arrhenius analysis yielded an interfacial hopping activation energy of 13.46 kJ/mol. Thermal analysis (DSC/TGA) showed increased glass transition temperatures (T _g) and enhanced degradation stability. Kinetic modeling via the Coats-Redfern method confirmed that TiO₂ incorporation elevates both the activation energy (E _a) and Gibbs activation energy (ΔG) for thermal breakdown. Raman spectroscopy identified local interactions between Ti⁴⁺ sites and the polymer π-system, suggesting that restricted segmental mobility at the interface governs both charge transport and thermal kinetics. This unified interfacial approach successfully explains the synergistic dielectric and thermal phenomena observed in the composite.

Electron-beam (EB) irradiation provides initiator-free crosslinking of polyethylene-based insulation materials, but its influence on the thermal degradation of halogen-free flame-retarded composites remains insufficiently understood. This study investigated the thermal stability and conversion-dependent degradation behavior of EB-crosslinked low-density polyethylene/ethylene-vinyl acetate (LDPE/EVA) composites containing aluminum trihydroxide (ATH), magnesium hydroxide (MH), and supplementary calcium carbonate using thermogravimetric analysis at multiple heating rates. Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Kissinger analyses were applied over α = 0.1–0.9. EB irradiation progressively enhanced thermal stability, increasing the maximum degradation temperature by approximately 40°C and the average apparent activation energy from approximately 160–165 kJ·mol⁻¹ for unirradiated materials to above 210 kJ·mol⁻¹ at the highest dose. Conversion-dependent activation-energy profiles varied systematically with irradiation dose, indicating changes in degradation behavior associated with network formation and competing chain-scission, crystallinity, and filler-related effects. Under equal-mass-loading conditions, MH-containing formulations exhibited higher degradation temperatures, apparent activation energies, and residue values than corresponding ATH-containing formulations. Overall, isoconversional analysis provides mechanistic insight into the combined effects of EB-induced structural modification and flame-retardant chemistry, supporting the development of thermally stable halogen-free polyolefin insulation materials for wire and cable applications.

The wound dressing with good injectability, self-healing ability, tissue adhesion, and especially antibacterial properties has significant potential in the healthcare field. Here, we developed an injectable hydrogel through the one-pot radical polymerization of acrylic acid (AA) in the presence of quaternized chitosan (QCS) and pre-formed polydopamine (PDA). In this system, the PDA-QCS-AA (DQA) hydrogel is primarily formed by the in situ polymerization of the hydrophilic anionic monomer AA within the natural cationic polysaccharide QCS. Due to the reversible physical crosslinking network, the hydrogel exhibits injectability and self-healing properties. In addition, the inclusion of the hydrophilic PAA network and adhesion molecules PDA and QCS endows the hydrogel with good adherence. Furthermore, thanks to the inherent antibacterial capability of QCS, this hydrogel demonstrates outstanding antibacterial performance. Moreover, the hydrogel also shows excellent biocompatibility. In vivo experiments indicate that this hydrogel dressing can significantly accelerate the healing of surgical site infected (SSI) wound models. These findings suggest that the injectable, adhesive, and antibacterial DQA hydrogel warrants further investigation as a dressing for infected surgical wounds.

Sulfur-rich vitrimers have attracted increasing interest due to their dynamic covalent networks and potential in sustainable materials. In this work, sulfur-based vitrimer networks were constructed via a two-step strategy by combining hydroxyl-functionalized oligosulfides with epoxy cross-linkers. The oligosulfides, containing dynamic oligosulfide (–Sx–) linkages, were synthesized through the oligomerization of elemental sulfur with cyclic disulfides, followed by cross-linking with bisphenol A diglycidyl ether or diethylene glycol diglycidyl ether in the presence of imidazole. By tuning the type and loading of epoxy cross-linkers, the resulting networks exhibit a wide range of mechanical properties, from rigid thermosets to soft and extensible materials, with tensile strengths up to 12.85 ± 2.73 MPa and elongations at break up to 44.40% ± 5.01%. In addition, these vitrimers demonstrate effective adhesive performance, achieving lap-shear strengths of up to 6.05 ± 0.99 MPa on steel substrates. This work provides a straightforward and versatile strategy for designing sulfur-rich vitrimer materials with tunable mechanical behavior and promising potential in structural adhesive applications.

4D printing, an emerging manufacturing technique incorporating a temporal dimension to enable shape/property evolution under stimuli, has gathered significant interest. However, biodegradable polymers suitable for low-cost fused deposition modeling (FDM)-based 4D printing that simultaneously combine low warpage, balanced mechanical strength, and stable thermal-responsive shape memory performance are still scarce. CO₂-incorporated aliphatic-aromatic copolyesters tailored for low-cost FDM-based 4D printing have not been systematically investigated. This study investigates the FDM process optimization, performance characterization, and 4D printing potential of a novel biodegradable polymer, poly-(propylene carbonate phthalate) (PPC-P). Key FDM parameters were determined as printing temperature 170°C–190°C, printing speed 40–50 mm/s, layer height 0.1–0.2 mm. The raster angle significantly affects mechanical performance: specimens printed at 90° raster angle achieve a maximum tensile strength of 33.1 MPa. Single-edge-notch three-point-bending tests confirm that intralayer bonding (G _fe = 2.62 kJ/m²) is superior to interlayer bonding (G _fe = 1.67 kJ/m²). The high-precision FDM fabrication of PPC-P was successfully achieved. Crucially, the printed specimens exhibit satisfactory thermally responsive shape memory effect: complete shape recovery (R _r reached 96.5%) occurs rapidly in 45°C water bath. This work provides a promising new biodegradable material option for FDM based 4D printing, with applications in temperature sensors and soft robotics.

Polylactic acid/hexagonal boron nitride (PLA/h-BN) thermal conductive composites hold broad application prospects owing to their electrical insulation and biodegradability. However, the conventional twin-screw extruder (TSE) based on shear fields struggles to achieve satisfactory in situ exfoliation of h-BN and tends to induce severe degradation of the PLA. This paper employed novel perturbation ring elements (PREs) to modify a dual-speed nontwin screw extruder (NTSE) based on a chaotic field for the large-scale preparation of high-performance PLA/h-BN thermal conductive composite. The results indicate that compared with TSE, NTSE exhibited shorter residence times and a narrower residence time distribution for the material, while the mixing index was significantly improved, which can achieve significantly better in situ exfoliation, dispersion, and distribution of h-BN in the presence of a lower degradation degree of PLA. Moreover, after the NTSE was further modified with PRE, this phenomenon became more pronounced. Compared with those prepared by TSE, PLA/h-BN prepared via NTSE-PRE exhibited in-plane and through-plane thermal conductivities increased by 26.6% and 16.9%, respectively, alongside intrinsic viscosity and weight-average molecular weight elevated by 21.5% and 20.0%, while the Young's modulus after annealing increased by 11.5%. This work provides a novel approach for the large-scale preparation of biodegradable polymer-based thermally conductive composites.

Impact polypropylene copolymer (IPC) is widely used commercially. Ethylene–propylene blocky copolymer (EbP) boosts IPC compatibility at the interface to realize an excellent rigidity-toughness balance, but the impact of its complex distribution on IPC multiphase properties is rarely studied. In this work, two industrial resins (Samples A and B) with similar flexural modulus but significantly different impact strength were analyzed for chain microstructure and copolymer distribution. Combined atomic force microscopy-infrared (AFM-IR), fractionation, chain-structure, and thermal analyses suggest that an EbP-enriched EP-copolymer interphase is preferentially formed in Sample A. In contrast, the stronger crystallization tendency of B100 (the 100°C elution fraction of Sample B) favors premature microphase separation and redistribution of the EbP fraction before crystallization of the isotactic polypropylene matrix, resulting in ethylene-containing copolymer-rich regions in both the dispersed phase and selected locations within the continuous PP phase. This less interface-confined distribution may weaken the compatibilizing effect of EbP and contribute to the poorer mechanical properties of Sample B. The lower molecular weight (M_w) and ethylene content of B100 facilitate the mobility, rearrangement, and crystallization of propylene segments. This work elucidates how the molecular characteristics and crystallization behavior of EbP influence its interfacial distribution and, consequently, IPC compatibility and toughness.

Amino-modified tetraphenylethylene (TPE), an aggregation-induced emission (AIE) fluorescent probe, was employed to investigate crystallization and phase separation of thermodynamically immiscible biodegradable poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends, whose interfacial and crystalline structures govern macroscopic properties but are hard to visualize via conventional methods. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) reveal that flexible PBAT segments enhance PLA chain mobility and crystallinity, whereas TPE restricts chain motion of both components and suppresses crystallization in neat homopolymers and their blends. Fluorescence microscopy confirms TPE preferentially accumulates in the PLA phase and enriches at the PLA/PBAT interface to form an interphase, enabling direct visualization of phase separation morphology. Thermogravimetric analysis (TGA) shows TPE reduces polyester chain entanglement and lowers the maximum thermal decomposition temperature of both phases. Scanning electron microscopy (SEM) of tensile-fractured surfaces indicates interfacially enriched TPE reduces interfacial tension and improves adhesion, but inhibits the debonding-cavitation toughening mechanism, decreasing tensile strength and elongation at break. Fluorescence intensity positively correlates with blend crystallinity, as rigid crystalline regions confine TPE intramolecular rotation. This work provides an intuitive in situ visualization strategy for correlating interfacial structure, crystallization and, performance of biodegradable polyester blends via AIE probes.