Journal of Applied Polymer Science最新文献

This study investigates the loss and restoration of release functionality in service-aged liquid silicone rubber (LSR) molds used for UV-curable epoxy injection. Repeated molding cycles and UV exposure were associated with epoxy-residue accumulation and surface oxidation, which reduced surface hydrophobicity and promoted demolding failure. Conventional water-based cleaning removed loosely bound contaminants and gave only temporary wetting recovery, indicating that cleaning alone did not restore the degraded surface chemistry. We therefore developed a regeneration protocol combining ultrasonic cleaning with baking at 140°C. X-ray photoelectron spectroscopy (XPS) and attenuated-total-reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) showed a decrease in silanol-related signals and recovery of the siloxane-rich surface after the combined treatment, consistent with outward migration of low-molecular-weight polydimethylsiloxane (LMW PDMS). The regenerated molds retained dimensional stability and achieved a > 44% increase in functional lifetime in a pilot-scale UV-epoxy injection process. These findings provide a practical regeneration route for extending the service life of LSR molds while clarifying the coupled roles of contaminant removal and thermally activated surface restructuring.

We develop a general strategy for preparing solvent-resistant coated natural rubber by constructing a chemically stable polymer layer on the surface of natural rubber via layer-by-layer self-assembly. The coating process entails the sequential layer-by-layer deposition of poly(diallyldimethylammonium) chloride (PDDA) and poly(styrenesulfonate) (PSS) onto the rubber surface, which is subsequently immersed in aqueous solutions of polyvinyl alcohol (PVA). The resulting coating effectively protects natural rubber from organic solvent erosion and dissolution, enabling the coated rubber to remain intact in toluene for over 15 h and in common oils for more than 7 days, without compromising its mechanical properties. By using this solvent-resistant coating, and integrating the humidity-sensitive property of PVA with the excellent mechanical performance of natural rubber, we uniformly deposit the PVA layer in the form of microdroplets onto one side of the curved surface of natural rubber. We fabricate a natural rubber material with humidity-responsive capability and extend its potential applications in the field of humidity sensors.

Polymer-based proton exchange membrane fuel cell (PEMFC) composite bipolar plates (CBPs) typically contain over 80 wt% conductive filler to fulfill the conductivity requirement, limiting PEMFC lightweighting. Utilizing multi-scale conductive fillers to optimize the conduction path is an effective strategy for enhancing filler efficiency. Herein, graphite flakes (GF) are selected as the primary conductive filler, and carbon black (CB) is used as the secondary filler to fabricate polybenzoxazine (PBA)-based CBPs via dry dispersion method. The impact of GF size and content, and GF/CB filler ratio on the conductivity and various service properties of CBPs are investigated. Results demonstrate that smaller-sized GF contributes to superior electrical performance. Owing to the selective distribution of CB within the PBA phase, the conductivity of PBA/GF/CB CBPs is substantially enhanced. At identical total filler loading, the binary PBA/GF CBP fails to meet the DOE target (100 S/cm), whereas the addition of 4 wt% CB brings the conductivity up to the DOE requirement (116.36 S/cm). Notably, the CBP containing 52 wt% GF and 8 wt% CB achieves the highest in-plane conductivity (153.12 S/cm) as well as the maximum power density (673.13 mW/cm²). Moreover, PBA/GF/CB CBPs also exhibit satisfactory flexural strength, thermal conductivity, corrosion resistance, and hydrophobicity.

This study employs KH560 to surface-modify nano-SiO₂, which is then melt-blended with PEEK to prepare composites with loadings of 0–7 phr. At 3 phr, the melting temperature rose to 348.5°C, the melting enthalpy reached a maximum of 80.33 J g⁻¹, and the corrected crystallinity remained comparable to that of pure PEEK, while the filler dispersion was the most uniform. Concurrently, the water contact angle decreased from 81.7° to 70.6°–72.8°, thermal conductivity increased substantially, and the dielectric breakdown strength nearly doubled, reaching ≈24.7 kV mm⁻¹ at 5 phr. Compared with the higher loadings commonly reported in the literature, significant multi-property improvements were achieved at only 3–5 phr. These results demonstrate that KH560 surface modification effectively enhances the thermal, crystallization, dielectric, and surface performance of PEEK at low filler contents.

The frequency-dependent viscoelasticity of bidisperse carbon black (CB)-filled natural rubber (NR) nanocomposites is investigated using coarse-grained molecular dynamics. The Payne effect becomes more pronounced with increasing frequency and strain amplitude. High frequencies cause extensive nanoparticle (NP) network disruption, reducing loss modulus. Low frequencies enable network reformation and chain friction, increasing loss modulus under large strains. The change in non-bonded interaction energy is dominated by CBCB interactions, with negligible NRNR and CBNR contributions on the normalized per-pair scale. A frequency-driven transition in the dominant CB pair is identified: same-sized pairs dominate at low frequencies, while heterosized pairs prevail at high frequencies. The frequency 2.5 × 10⁻⁵ fs⁻¹ marks a characteristic point where the NP network maximally constrains chain mobility. These findings establish that the Payne effect is primarily governed by NP network dynamics, with heterosized CB pairs playing a key role in modulating the frequency-dependent energy dissipation.

The removal of phenolic pollutants and synthetic dyes from wastewater remains an important environmental challenge due to their potential adverse effects. In this study, single- and double-layer adsorptive composite membranes based on cellulose acetate (CA) and polyvinylpyrrolidone (PVP) are developed by solvent evaporation-induced phase separation (EIPS). Commercial powdered activated carbon (PAC) and two untreated agro-waste bioadsorbents, almond shells (Ash) and date pits (Dp), are incorporated either within the polymer matrix or deposited on the membrane surface. The influence of adsorbent nature and location on phenol and methylene blue removal is investigated. The double-layer membrane D.L(INS(PAC), SRF(Ash)) exhibits the highest methylene blue removal (60%) in both single- and mixed-pollutant systems, while its Ash-containing surface layer reaches 70% removal when tested separately. In comparison, D.L(INS(PAC), SRF(Dp)) achieves approximately 50%, whereas membranes with Ash or Dp incorporated internally and PAC deposited on the surface show less than 30% removal. Phenol removal remains limited (20%–30%) for all membranes. FTIR analysis confirms interactions between CA and the adsorbents, while contact angles of 47.7°–55° indicate hydrophilic surfaces. The results highlight the importance of adsorbent positioning for methylene blue removal.

The aim of the current study was to extract lignin-rich fraction from date palm ( Phoenix dactylifera L.) seeds and evaluate its application as a filler in sodium alginate-based films for food packaging applications. Lignin was isolated through a sonication-assisted mild alkaline hydrolytic process followed by acid precipitation. The isolated lignin was then characterized by using FTIR, XRD, SEM, and DSC analysis. FTIR analysis confirmed the presence of characteristic hydroxyl and aromatic functional groups associated with lignin. XRD analysis showed a low-crystallinity with a broad diffraction region linked with amorphous lignin. SEM analysis showed an irregular and porous morphology. DSC demonstrated favorable thermal behavior. Sodium alginate and lignin films were developed by adding lignin into the sodium alginate matrix at various concentrations by using the solution casting method. The light transmittance and water vapor transmission rate decreased with the addition of lignin. The haze value and antioxidant activity of the films increased with the increase in lignin concentration and improved the light-blocking ability. However, incorporating lignin did not significantly modify the mechanical properties of the films. The sample with the highest lignin concentration showed improved surface hydrophobic properties. These findings suggest that the date seed-derived lignin could be a suitable candidate for food packaging applications.

The previously reported naphthalenediimide (NDI)-bridged donor–acceptor type electroactive monomer (NDI-H-T) was synthesized according to the reported procedure and electropolymerized onto a graphite pencil electrode (GPE) surface to obtain a conductive p(NDI-H-T) film. Subsequently, gold nanoparticles (AuNPs) were electrodeposited onto the polymer-coated electrode surface, and glucose oxidase (GOx) was immobilized to fabricate the GPE/p(NDI-H-T)/AuNPs/GOx enzymatic glucose biosensor. The developed biosensor was characterized by cyclic voltammetry (CV) using a three-electrode system with Ag/AgCl, Pt, and modified GPE electrodes. Experimental parameters including electrode type, electropolymerization cycle number, electrolyte pH, and enzyme immobilization time were systematically optimized. Under optimized conditions, the proposed biosensor exhibited a linear response toward glucose within the concentration range of 0.0189–3.21 mM, with limit of detection (LOD) and limit of quantification (LOQ) values of 8.1 × 10⁻³ mM and 0.0269 mM, respectively. Furthermore, the biosensor demonstrated satisfactory selectivity against common interfering species and was effectively used for glucose detection in pomegranate juice samples. The obtained results demonstrated that the p(NDI-H-T)/AuNPs/GOx biosensor provides an effective platform for electrochemical glucose sensing applications.

Epoxy resins (EPs) possess excellent mechanical strength, chemical resistance, and adhesion, yet their inherent flammability limits their use in fire-sensitive applications. Under increasingly stringent safety requirements, developing simple and scalable halogen-free flame retardants remains a significant challenge. In this work, a phosphorus–nitrogen flame retardant, 6-(2-(1H-imidazol-1-yl)ethyl)dibenzo[c,e][1,2]oxaphosphinine 6-oxide (DIM), was synthesized via a one-step nucleophilic addition reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 1-vinylimidazole (VIM), and subsequently incorporated into epoxy thermosets, either alone or in combination with melamine (MEL). Fourier-transform infrared spectroscopy (FTIR) was used to evaluate the formation of DIM. The thermal degradation, fire performance, char structure, phosphorus retention, and evolved products of the resulting thermosets were investigated using thermogravimetric analysis (TGA), cone calorimetry, scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), TGA coupled with Fourier-transform infrared spectroscopy (TG-FTIR), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Changes in the characteristic FTIR bands of the PH and vinyl groups, together with the retention of the DOPO and imidazole frameworks, supported the formation of the proposed addition product. Among the investigated formulations, EP/DIM-MEL4 exhibited the greatest improvement in fire performance, with reductions of 31.9% and 36.0% in peak heat release rate and total heat release, respectively, relative to neat EP. Microscopic and spectroscopic analyses indicated the formation of a more expanded, continuous, and structurally ordered protective char. ICP-OES analysis showed that approximately 31.1% of the initial phosphorus was recovered in the solid residue. TG-FTIR and Py-GC/MS further suggested that volatile phosphorus-containing species contributed to gas-phase radical inhibition, whereas nitrogen-containing volatiles derived from the imidazole moiety and MEL contributed to flame-zone dilution. Overall, the improved fire safety of the DIM-containing epoxy thermosets is attributed to the combined effects of gas-phase inhibition and condensed-phase barrier formation. This work provides a simple strategy for developing DOPO-based phosphorus–nitrogen flame-retardant systems for epoxy thermosets.