Journal of Applied Polymer Science最新文献

Melamine (triazine)-based crosslinkable waterborne polyurethane (WBPU) dispersions were prepared with defined dimethylolpropionic acid (DMPA, 21.10 mol%) and triazine (0.50 mol) contents. The hydrophobic properties (determined by water swelling (%) and water contact angle), mechanical strength, and adhesive strength of the respective coatings were evaluated. Compared with those of pristine WBPU, the hydrophobicity, adhesion strength, and mechanical strength of crosslinked WBPU increased. The interactions between the urethane-urea groups and triazine and its derivatives 2,4-diamino-6-dimethylamino-1,3,5-triazine (D1), 2,4-diamino-6-diethylamino-1,3,5-triazine (D2), 2,4-diamino-6-butylamino-1,3,5-triazine (D3), and 2,4,6-tris[bis(methoxymethyl)amino]-1,3,5-triazine (D4 or HMMM) were investigated using density functional theory (DFT) optimization at the M06-2X/6-31+G(d,p) level. The DFT results revealed that D4 exhibited the strongest interaction energy and formed hydrogen bonds with WBPU. These theoretical findings strongly matched the experimental findings, because the coating with HMMM improved the protective properties among all the coatings. The addition of defined poly(ethylene oxide) glycol (PEG) also increased the shelf life of the dispersion without sacrificing material properties.

The effect of four wood fibers (Rosewood, White oak, Black walnut, Classic birch)/PLA composites was studied, which were prepared by 3D printing technology. Considering the actual service environment, the short-term hydrothermal test was performed, and the wear and mechanical behavior of four wood fibers/PLA composites were characterized. The characterization results indicated that the Rosewood fiber/PLA composite had better mechanical properties than the other wood fibers; the addition of wood fiber can improve its wear resistance, deformation resistance and water resistance ability. The improvement of key indicators can be observed by the surface microstructure and cross-sectional microstructure morphology, Stable and stronger interfacial adhesion resulted in better deformation and heat resistance ability. However, after short-term hydrothermal aging, these obvious interfacial defects led to the decline of wear resistance and deformation resistance ability. There are a lot of gaps between the fiber and matrix, which raised an increase in water absorption. These data are beneficial for the application of wood fibers in composites with PLA matrix.

This study systematically analyzes the volumetric swelling behavior and plugging control mechanism of interpenetrating polymer network (IPN)-based swelling particles. This addresses the issue of existing evaluations relying primarily on swelling multiple based on mass, which fails to meet the field requirements for matching particle size with pore-throat plugging of reservoirs. IPN particles were prepared using stepwise and synchronous methods. Their microstructures, swelling rates, volumetric swelling multiples, and the effects of temperature and salinity on swelling behavior were tested and analyzed. Furthermore, a plugging control particle size calculation model was established. Due to the influence of network compactness, the volumetric swelling multiples of IPN particles increased by 8.1%~17.0% or decreased by 13.0%~27.9% compared to conventional PAAm-MBA. The increase of temperature promoted amide group hydrolysis and chain relaxation, enhancing volumetric swelling multiples by 55%, while salinity suppressed swelling by shielding hydrophilic groups, reducing it by 58%. The swelling process was divided into three stages: capillary water absorption, chain relaxation, and osmotic pressure control, conforming to non-Fickian diffusion. The “permeability–pore-throat size–migration time–volumetric swelling multiple–initial particle size” associated control calculation model enables precise design for deep-profile particle plugging. The research results provide a theoretical basis for the design and field application of swelling particles.

Diimine-nickel catalysts usually show low activity and poor polyethylene properties during ethylene polymerization at high temperatures, which can be addressed by precise tuning of the ligand structure. In this study, a series of unsymmetrical 1,2-bis(imino)acenaphthene-nickel(II) complexes bearing a fixed, sterically demanding 2,6-dibenzhydryl-4-(benzhydryloxy)phenylimine and systematically varied N-aryl substituents were synthesized and evaluated for ethylene polymerization. These complexes are well characterized by FTIR, elemental analysis and single crystal x-ray diffraction (Ni2 ^Et and Ni5 ^Et ). Polymerization behavior was strongly influenced by both cocatalyst choice and reaction conditions, with EASC delivering the highest activity (up to 1.34 × 10⁷ g·mol⁻¹·h⁻¹) and producing high molecular weight (2.0–11.6 × 10⁵ g mol⁻¹), semicrystalline polyethylene, while MMAO produced more amorphous materials with lower melting points. Of significant note, high-temperature polymerization demonstrated excellent catalyst thermal stability, with maintained activity of 1.8 × 10⁶ g·mol⁻¹·h⁻¹ and molecular weight of 2.1 × 10⁵ g mol⁻¹ at 100°C. Sterically less hindered N-aryl groups favored higher activity, whereas bulkier substituents promoted chain propagation for higher polymer molecular weight polyethylene. Change of steric substituent resulted in precise control over crystallinity (X _c: 5.7 to 80.8%), which showed a strong relationship with the mechanical properties of resulting polyethylene, displaying high tensile strength (up to 11.6 MPa) and elongation at break (up to 586%). Compared to previous unsymmetrical nickel catalysts, these polyethylenes offer enhanced tensile performance, emphasizing the structural control exerted by the catalyst structure on material properties.

Here, we report the preparation of large-sized gelatin capsules via a dipping method. The surface properties of the capsules were engineered via glutaraldehyde crosslinking and epoxy resin grafting to enhance hydrophobicity and crosslinking density. Soil column leaching tests with urea-loaded capsules demonstrated an excellent sustained-release profile, characterized by a low initial release (4.5% within 24 h) and prolonged nutrient release (78.4% over 28 days). Beyond improving fertilizer efficiency, this capsule system offers a versatile platform for co-encapsulating multiple agrochemicals, such as fertilizers and pesticides. This work successfully bridges pharmaceutical capsule technology with the field of agricultural controlled-release fertilizers.

Feminine hygiene products made of natural fibers offer a health-conscious alternative to the adverse effects of synthetic sanitary products on women's health and the environment. However, sanitary napkins, rags, or cloth composed of natural materials are prone to deadly pathogen growth and decomposition if not properly treated or maintained. In this article, we report a blend of essential oils consisting of lavender, tea tree, ylang–ylang, bergamot, rose, and sandalwood with odor profiles such as fresh, floral, aromatic, and woody notes with antimicrobial effects for a single-use application on feminine hygiene products. Microencapsulation of the blend into β-cyclodextrin-grafted chitosan (β-CD-g-CS) was obtained by combining emulsification (O/W) and freeze-drying methods. Emulsification in the presence of Tween 80 afforded a greater number of spherical microcapsules of average size 4.35 μm with 70.78% encapsulation efficiency. TGA revealed that the Tween 80 assisted perfume-encapsulated microcapsules exhibited very high heat resistance (157°C). When an aqueous suspension of the blend-encapsulated microcapsules was applied to the jute pulp, it exhibited > 98% antimicrobial growth against both Gram-positive and Gram-negative bacteria and fungi. Therefore, incorporating microencapsulated essential oil blends as natural antibacterial agents can be an effective approach to promote healthier menstrual hygiene management.

Long-chain epoxy resins are increasingly adopted in high-voltage insulation systems due to their low curing exotherm, improved toughness, and superior dielectric properties. These resins are typically synthesized via chain extension between bisphenol A and short-chain epoxy precursors. However, during pilot-scale production, inadequate heat dissipation often leads to thermal overshoot, inducing undesirable side reactions and structural irregularities. In this study, we investigate how reaction-induced thermal fluctuations affect the molecular architecture of chain-extended epoxy resins and, consequently, the performance of their cured insulation materials. Differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) analyses reveal that thermal overshoots exceeding 20°C promote side reactions between hydroxyl and epoxy groups, resulting in increased molecular branching, higher viscosity, and compromised processability. These structural changes further lead to reduced crosslinking uniformity, manifested by lower crosslink density, diminished mechanical toughness (impact strength decreased from 26.4 to 24.1 kJ/m²), and deteriorated dielectric performance (volume resistivity dropped from 2.58 × 10¹⁷ to 1.94 × 10¹⁷ Ω ·cm). This work provides mechanistic insight into the interplay between reaction conditions and structure–property evolution, offering practical guidance for the controlled and scalable production of high-performance epoxy insulation materials.