Journal of Applied Polymer Science最新文献

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.

The demand for sustainable construction materials facilitates the development of alkali-activated slag (AAS) as an alternative cementitious material to cement, while the poor workability of AAS is one of the key problems limiting its practical applications. This study systematically investigates the structure-performance relationships of poly(acrylic acid-co-2-acrylamido-2-methylpropanesulfonic acid) (AA-co-AMPS, PAS) copolymers as superplasticizers for AAS systems. Two model PASs with distinct monomer ratios (AA:AMPS = 0.1 and 15) are synthesized and characterized. PAS15, with higher carboxyl group density and charge density, demonstrates superior dispersion efficiency and fluidity retention in moderate-alkalinity systems (4 wt% Na₂O) attributed to enhanced adsorption and Ca²⁺ chelation. Conversely, PAS0.1, enriched in hydrophobic AMPS units, outperforms PAS15 under high alkalinity (8 wt% Na₂O) due to alkaline-induced aggregation on particle surface providing steric stabilization. In situ calorimetry and ¹H LF-NMR reveal PAS15's stronger retardation effect on alkali-activated reaction, extending induction period and delaying gel formation. Pore solution analysis confirms PAS15's ability to suppress slag dissolution and Ca²⁺ consumption by gel formation, contributing to the prolonged fluidity retention. Both copolymers preserve early-age compressive strength, demonstrating compatibility with AAS mechanical development. This work establishes a molecular design framework for the superplasticizers tailored for AAS, balancing electrostatic repulsion, steric hindrance, and chelation effects to address the challenges in dispersing AAS.

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.

Conductive polymer composites (CPCs) are promising candidates for flexible electronics and structural health monitoring. However, their practical application is often hindered by the shoulder peak effect—a non-monotonic rebound in the resistance–strain curve during unloading that compromises sensing accuracy and signal stability. Although previous studies have mainly focused on experimental observations, the molecular-level origin of this phenomenon remains insufficiently understood. In this work, experimental characterization is combined with molecular dynamics (MD) simulations to elucidate the interfacial interactions in graphene (GR)/ethylene–propylene–diene monomer (EPDM) composites. The results reveal that the shoulder peak effect primarily arises from the mismatch between the viscoelastic hysteresis of the EPDM matrix and the reconstruction of the conductive network. Notably, the composite containing 4 wt% GR forms a more uniform and stable conductive network with the strongest interfacial adhesion, significantly suppressing the shoulder peak effect. MD simulations further confirm that this formulation exhibits the highest interfacial binding energy and the most compact structural configuration. Overall, this study provides mechanistic insight and practical guidelines for designing high-reliability flexible strain sensors based on CPCs.