Journal of Applied Polymer Science最新文献

Electrical treeing, an irreversible degradation process in dielectric polymers under high electrical stress, critically threatens the reliability of power equipment by propagating undetectable damage. To address this challenge, magnetically responsive microcapsules were developed for targeted electrical tree repair. These microcapsules are magnetically positioned within dielectric encapsulants and engineered with a higher dielectric constant than the host matrix to guide electrical trees toward microcapsule rupture. The core-shell structure integrates: (i) a hybrid healing agent (photosensitive hyperbranched polyurethane acrylate/epoxy resin) and (ii) functional shells incorporating Fe₃O₄@SiO₂ nanoparticles for magnetic navigation and titanium dioxide/graphitic carbon nitride (TiO₂/g-C₃N₄) for UV-shielding. During electrical tree propagation, electroluminescence triggers polymerization of the released healing agent, enabling autonomous crack-sealing. Optimized microcapsules achieve 75% encapsulation efficiency with uniform size distribution (~100 μm). After optimization, a doping concentration of 4 wt% was identified as optimal, at which the composite exhibited a peak tensile strength of 37.54 MPa (compared to 36.21 MPa for the neat resin) and a minimal reduction in breakdown voltage to 36.4 kV (from 37.2 kV). In situ optical microscopy confirms effective damage repair during tree growth, demonstrating a precision self-healing strategy that extends service life without compromising intrinsic material properties.

Designing char-forming agents as multifunctional components provides a practical direction for developing intumescent flame-retardant materials with excellent fire safety. In this work, a novel bio-based macromolecular charring agent (NL-OH) was synthesized by chemically modifying lignin with pentaerythritol (PER) and melamine (MEL) and compounded with ammonium phosphate (APP) at an optimal ratio of 5:4 to construct an intumescent flame-retardant system (IFRR) for polypropylene (PP). The flame retardancy and mechanism of the fabricated composites were evaluated using LOI, UL-94, TGA, CCT, TG-FTIR, and other techniques. With the synergy between NL-OH and APP, PP composites exhibited outstanding LOI values of 32.9%, significant char-forming ability of 10.71% of char residues, and notable reductions in the peak heat release rate (PHRR) and peak smoke production rate (PSPR) by 46.9% and 80.9%, respectively. NL-OH functioned as both a charring and blowing agent, promoting the formation of an expanded and continuous char layer that effectively insulates heat and suppresses flammable gas release, contributing to the overall fire safety of the material. This study aligns with international efforts toward sustainable and eco-friendly flame-retardant technologies, which provide a theoretical basis for the construction of a dual-source charring agent.

We have investigated the mechanical strength of sideweld sealing for biaxially oriented polypropylene bags. The tensile strength of the seal of the biaxially oriented polypropylene films showed a smaller deviation with increasing crystallinity in the sealed zone. Because the distribution of the crystallinity indicated sufficient homogeneity within the sealed zone at the microscopic level, the smaller deviation of the sealing strength with increasing crystallinity is ascribed to the formation of macroscopic defects under stretching. The defects around the sealed zone were visualized by photoelasticity observation under tensile stretching. We observed fluctuation of the strain near the sealed zone, accompanied by wavy patterns owing to the troughs induced by the shrinkage stress perpendicular to the stretching direction. Cross-sectional observation of the sealed zone in the sideweld sealed specimen after the tensile test suggested that the fracture was initiated by ductile fracture. The subsequent fracture process became more brittle for specimens with lower strength, presumably because of the higher crystallinity. We also confirmed that the crystallinity can be controlled by the cooling rate in a rapid-cooling experiment mimicking the air cooling in the bag forming process, where the crystallinity was significantly reduced by about 15%.

The present work investigates two methods for preparing defect-free, symmetric membranes of the thermochemically robust polymer, poly(2,5-benzimidazole) (commonly known as ABPBI) for forward osmosis (FO), a growing technology for niche separations. The obtained polymer and membranes were analyzed for physical properties of significance. The FO analysis was performed using three salt solutions, viz., sodium chloride (NaCl), magnesium chloride (MgCl₂), and sodium sulfate (Na₂SO₄). The effects of casting methodology (solvents present in the dope), membrane heat treatment, draw solution concentration, long-duration analysis, and FO-assisted enrichment of organic acids were evaluated. Some of the membranes exhibited extremely low reverse salt flux (RSF), which conveys the novelty of these membranes. Some of these membranes were analyzed using a high draw solution (DS) concentration (4 mol L⁻¹) to enhance water flux and further employed to enrich organic acids. The aqueous acetic and methacrylic acid concentrations were enriched from 4.89 and 2.93 mol L⁻¹ to 11.88 and 10.01 mol L⁻¹, respectively. These results demonstrate an unmet need of concentrating methacrylic acid (a temperature-sensitive compound possessing a double bond). The present work demonstrates the potentials of ABPBI-based symmetric, thin membranes for FO and their industrial applicability for the first time.

This study pioneers the development of Eudragit/poly(ε-caprolactone) (EU/PCL) nanofibers as a novel carrier for the bioactive flavonoid, 2,3-diphenyl-3-hydroxyflavone derivative. The compound, encapsulated at two concentrations, was evaluated in parallel with diclofenac diethylamine (DEA), a well-known nonsteroidal anti-inflammatory drug (NSAID). Physicochemical analyses confirmed the formation of uniform, bead-free nanofibers with a hydrophobic surface morphology. Drug release investigations highlighted a sustained release profile, with 44.94% of the encapsulated drug released within 40 h in vitro. The release kinetics exhibited an excellent correlation with the Korsmeyer–Peppas model (R ² = 0.9315), suggesting a diffusion-driven mechanism coupled with polymer erosion. Remarkably, the fabricated nanofibers demonstrated anti-inflammatory efficacy comparable to diclofenac sodium, validated through inhibition of bovine and egg albumin denaturation assays. Biocompatibility was further established using HEK-293 cell culture studies, which revealed a high cell viability of 89.99% ± 0.60% across tested concentrations. In addition, the system achieved 68.11% ± 0.23% inhibition of albumin denaturation with an IC₅₀ value of 32.5 ± 0.23 μg/mL, underscoring its potent anti-inflammatory activity. Collectively, these findings establish EU/PCL nanofibers as a promising platform for the sustained delivery of 2,3-diphenyl-3-hydroxyflavone derivative, offering significant potential as a biocompatible and effective therapeutic alternative under in vitro conditions.

Reinforced and toughened polyethylene fishing fibers have garnered increasing attention to meet the operational demands of modern fisheries. In this study, modified ultrahigh molecular weight polyethylene (UHMWPE) granules, incorporating high-density polyethylene (HDPE) particles and 15 wt% granule powder, were prepared to fabricate reinforced polyethylene fibers. Building on this, the effect of thermoplastic elastomer (TPE) toughening modification on the structure and properties of UHMWPE fibers was investigated. Transmission electron microscopy (TEM) revealed that the TPE phases were uniformly dispersed within the continuous UHMWPE matrix, forming a distinct morphology. The degree of orientation (f ₁₁₀) generally increased with rising TPE content, indicating that TPE promotes orientation. The interaction between TPE content and drawing ratio (DR) enhanced the knot strength of the blended fibers and reduced the strength loss ratio. This study discusses the effects of TPE content on the morphology, crystalline structure, thermal properties, and mechanical performance of the doped fibers. Based on these findings, a mechanism by which TPE modifies UHMWPE fibers is proposed. The main effects of TPE content and DR, as well as their interaction on tensile properties, have been analyzed using analysis of variance (ANOVA).

Processing route plays a decisive role in tailoring the multifunctional performance of carbon nanofiber (CNF)-reinforced polymer nanocomposites. Here, melt mixing and solution processing were compared to evaluate their influence on volume resistivity, thermal conductivity, and electromagnetic interference (EMI) shielding. Solution-processed composites achieved superior conductivity at lower CNF loading (1.0 wt%) due to improved dispersion and network formation, while melt-mixed composites required higher loading (3.0 wt%) for comparable performance. Thermal conductivity and EMI shielding effectiveness also improved with increasing CNF content, with absorption dominating the shielding mechanism. These findings highlight the potential of CNF-reinforced polymer composites for advanced electrical and EMI shielding applications, with processing route playing a key role in tailoring multifunctional properties.

When used outdoors, polyethylene (PE) film is exposed to ultraviolet radiation with a wavelength of 300 nm, causing molecular chain breakage and leading to deterioration of the film's mechanical properties. To enhance the film's weather resistance, this study modified nano-ZnO (zinc oxide) using different coupling agents. The ultraviolet transmittance and mechanical properties of PE films modified with nano-ZnO incorporating various coupling agents were investigated. The γ-aminopropyltriethoxysilane coupling agent (KH550) was selected. The KH550-ZnO/PE film achieved a tensile strength of 34.2 MPa while providing effective UV shielding with minimal visible light blocking. The aging behavior of KH550-modified nano-ZnO-filled PE films under indoor accelerated aging conditions was investigated. By comparing the mechanical properties and UV shielding performance of PE films with varying nano-ZnO concentrations, the optimal loading was determined to be 4 wt%. PE films containing 4 wt% nano-ZnO demonstrated superior weather resistance in pure UV aging tests, maintaining 88.22% tensile strength retention after 40 days of pure UV exposure. In thermo-oxidative aging tests without UV influence, the 4 wt% maintained a tensile strength retention rate of 69.23%. However, in the thermo-oxidative photoaging test, the presence of moisture led to increased hydroxyl radical generation under the photocatalytic effect of nano-ZnO. This resulted in degradation of the modified PE film segments by hydroxyl radicals, manifesting as reduced tensile strength. Furthermore, three-dimensional polymer aging visualization revealed that changes in carbonyl and carboxyl groups within the film also followed the aforementioned aging patterns. This work aims to extend the service life of agricultural films used in high-temperature, dry environments by incorporating modified nano-ZnO.

In injection molding processes of semi-crystalline polymers, different cooling rates occur at the mold walls and in the part center leading to an inhomogeneous melt solidification and the formation of locally different spherulitic microstructures. To determine their effect on the local thermo-elastic properties and their impact on the part warpage, a multi-scale simulation scheme is used here to investigate the injection molding of an α-iPP stepped plate. After modeling the melt flow during the injection phase, the residual packing pressure is determined in the cooling phases. Then, the formation of the spherulite microstructure is calculated over a plate section with an athermal nucleation model. Based on the predicted effective lamella properties, the radial spherulite model is extended here. It permits deriving more accurate and less anisotropic effective thermo-elastic properties. The local mechanical properties vary strongly in accordance with the local crystallization degree. A generalized plane strain model is used to predict the warpage and shrinkage of the plate section during the in-mold cooling phase and after ejection. Simulations with either constant, mean properties or local ones show clearly that crystallization-dependent properties predict more accurately the warpage and shrinkage behavior compared to constant properties over the plate section.