Polymer Science, Series B最新文献

Epoxy vitrimers with high cross-linking density and rigid structures were synthesized by reacting of epoxy monomers containing rigid benzene rings with small-molecule curing agents. While the poor toughness (elongation at break ~10%) of epoxy vitrimers limited their applications in the fields of sealing, vibration damping, and impact resistance. In this study, bisphenol A epoxy resin (E44) was employed as the epoxy monomer, and carboxyl-terminated polybutylene adipate (PBA, M_n = 1700–5200) with flexible long chains was used as the curing agent to prepare E44/PBA epoxy elastomers containing dynamic ester bonds. Studies showed that as the molecular weight of PBA increased, the cross-linking density gradually decreased, while the crystallinity progressively increased, thereby influencing the thermal stability, mechanical properties and flexibility of E44/PBA networks. E44/PBA exhibited good thermal stability T_i (306–329°C) and high flexibility ε_b (295.12–553.94%). Among them, E44/PBA₁₇₀₀ demonstrated excellent self-healing, welding, and reprocessability, owing to the highest cross-linking density and abundant β-OH ester bonds, which readily allowed the topological network rearrangement of the epoxy networks. The scratch on E44/PBA₁₇₀₀ could be almost completely healed at 180°C for 30 min. Moreover, the welded E44/PBA₁₇₀₀ exhibited a load-bearing capacity of 200 g after welding at 160°C for 10 min, which was 450 times its own weight. This work supplied a feasible method to prepare epoxy elastomers with high toughness, self-healing, and recyclability.

In this study, boron was added to urea-formaldehyde resin’s structure, dry spinning and heat curing were then used to create boron-modified urea-formaldehyde fiber (BUFF). Which improved the fracture strength and toughness of urea-formaldehyde fibers. The chemical and morphological characteristics of the resultant fiber samples were investigated utilizing Fourier transform infrared spectroscopy (FTIR) and ¹³C nuclear magnetic resonance analysis (¹³C NMR). The thermal stability properties of various fibers were examined through thermogravimetric analysis (TGA), while their tensile strength was assessed using a tensile tester. The results demonstrated that boron was incorporated into the urea-formaldehyde molecules via B‒O bonds, which subsequently enhanced the three-dimensional network cross-linking within the fibers. This incorporation significantly improved the mechanical properties of the urea-formaldehyde fibers. The breaking strength of urea-formaldehyde fibers, thermally cured at 180°C for 20 min with the addition of 4% boric acid, was determined to be 481 MPa, reflecting a 138% enhancement over the original strength. The elongation at break was measured at 7.0%, indicating a 94% improvement from the initial value. Moreover, the thermal properties of the fibers were significantly improved, evidenced by a 20°C increase in the onset decomposition temperature and a residual carbon content of 28.47%.

The rapid expansion in the adoption of renewable energy sources, particularly through the use of photovoltaic panels, highlights the pressing issue of recycling these modules making it increasingly relevant today. Currently, approximately 90% of solar panels reach the end of their lifecycle through burial. The polymer components found in crystalline solar panels, such as ethylene vinyl acetate copolymer and polyvinyl fluoride, pose substantial environmental risks when disposed of in landfills. In this study, we investigated the toxicity associated with the polymer components of polycrystalline solar panels at the end of their operational lifespan. Our goal was to illuminate the correlation between the toxicity of these materials and various environmental factors. We primarily utilized biotesting techniques, drawing upon the chemotactic responses of the protozoan Paramecium caudatum, which allows for the detection of even trace amounts of substances that may be missed by other analytical approaches. The impact of poorly soluble compounds, such as the polymer materials found in solar panels, has not yet been investigated using this test organism. Following our experiments, we conducted a statistical analysis to evaluate how the toxicity levels found in polymer waste correlate with factors such as exposure duration, temperature, and sample fraction size. Our analysis highlighted significant factors influencing the fluctuation of toxicity indices in the components of end-of-life solar panels, leading to the creation of models that illustrate changes in toxicity with varying temperature and extraction time. Statistical analysis (ANOVA, p < 0.05) confirmed that exposure time is the most significant factor increasing the toxicity index (T) of polymers. The obtained logarithmic models (R² > 0.94) predict an increase in the toxicity of leaching of panel components in landfills, which indicates the environmental risks of their disposal and the need to develop disposal regulations.

The patterns of emulsion polymerization of methyl methacrylate or styrene in the presence of random copolymers of N,N-dimethylaminoethyl methacrylate with a small amount of methyl acrylate or methyl methacrylate units with a terminal trithiocarbonate group were investigated. It has been found that the rate of polymerization increases with decreasing pH of the dispersion medium, while higher conversion limits were achievable when less hydrophobic copolymer and more hydrophobic monomer (styrene) had been used. The resulting polymer suspensions differ in particle size distribution, depending on the monomer used. The particles in the polymer suspensions had a high positive charge on their surface, remained stable, and exhibited controlled behavior in response to changes in pH. It has been shown that the synthesized suspensions exhibit adhesion to hydrophilic surfaces and resistance to fungus.

In this study, the preparation of diphenylsilylene diol (DP)-modified double-A epoxy resin (E51) with resveratrol-functionalized graphene (Res/rGO) composites and their performance characterization were investigated. Firstly, the double-A epoxy resin (EP) was modified with DP to improve its mechanical properties and thermal stability. Then, Res/rGO was introduced into the modified epoxy resin (DP/E51), and a series of modified epoxy resin/resveratrol functionalized graphene (Res/rGO-DP/E51) composites were prepared. The effects of different graphene contents on the mechanical properties of the materials were analyzed by conducting tensile property tests on the composites. The results showed that the DP-modified epoxy resin exhibited a significant improvement in tensile strength, especially after the introduction of an appropriate amount of Res/rGO, the tensile properties of the composites were further optimized. Resveratrol, as a natural antioxidant substance, significantly improved the interfacial bonding and dispersion of the composites after functionalization on the graphene surface, thus enhancing the overall performance of the composites. In addition, the Res/rGO-DP/E51 composites exhibited excellent thermal stability, which has a good application prospect.

This study explores the influence of sulfur and peroxide (DCP) curatives on epoxidized natural rubber (ENR)/ethylene vinyl acetate (EVA) blends prepared via melt mixing at 160°C. The effect of these curatives on cure, tensile strength, fatigue and thermal degradation behavior etc. were examined. Although it was observed that the amount of EVA in the blend significantly affected the overall performance of the vulcanizates, however the ENR/EVA-sulfur cured compounds generally exhibited better physico-mechanical than the DCP-cured samples. For example, the sample E (70 phr ENR/30 phr EVA-Sulfur cured) attained about 60% higher cure rate than the sample A (70 phr ENR/30 phr EVA-DCP cured). Also, the sample E exhibited an extreme fatigue life performance (~1.7 × 10⁴ cycles at 15% strain) which was over 170 000% higher than sample A which obtained fatigue life of 10 cycles at the same strain. Again, the sample E obtained over 1200% tensile strength higher than the counterpart sample A. Even in an unfilled state, the sulfur-cured compounds (D and E) exhibited high physico-mechanical properties than the DCP-cured counterparts including related blends containing high reinforcements (30~50 phr) contained in literature. Therefore, further engineering of such materials could render them as suitable blends for developing rubber articles like O‑rings, gaskets, heat sinks and tread compounds.

In this paper, acrylic acid based light-responsive molecularly imprinted polymers were synthesized for the molecular recognition of methylene blue with light regulation performance, enriching their application environments. The template-rebinding/-release studies of the molecularly imprinted polymers showed that their affinity of the adsorption recognition sites were successfully regulated by the cis-trans isomerization of the azo group in the polymers. Rebinding isotherms and rebinding kinetics show that the adsorption of methylene blue by imprinted materials conforms to the single-layer chemical adsorption and pseudo-second-order kinetic model.

A new monomer of the norbornene series, containing a substituent with 9,10-dihydroanthracene fragment and a bromine atom has been synthesized with a yield of 47% using the Diels–Alder reaction between norbornadiene-2,5 and 2-bromanthracene. Its metathesis and additive polymerizations have been investigated. The sorption properties of the two obtained polymers, as well as the gas transport properties of the metathesis polymer, have been investigated. It has been shown that the presence of polar bromine atom in the side chain does not affect the properties of the polynorbornenes with 9,10-dihydroanthracene moiety: like similar polymers without bromine atoms, the synthesized polymers have exhibited a moderate level of gas permeability, a large free volume, and a large specific surface area (540 m²/g in the case of the additive polymer). The polymer obtained by metathesis polymerization has shown slightly lower values of ideal gas separation selectivity of CO₂-containing gas pairs compared to the unsubstituted analog, but higher O₂/N₂ selectivity. Such bromine-containing polynorbornenes may be of potential interest as materials for the storage and separation of gases, the properties of which can be tuned using polymer-analogous transformations.

Silicon-modified urea–formaldehyde fibers (SiUFF) were prepared by adding different proportions of phenyltriethoxysilane to urea–formaldehyde resin, which were then subjected to dry-spinning and curing treatment. The SiUFF were characterized by Fourier infrared spectroscopy, micro-infrared analysis and ¹³C nuclear magnetic resonance analysis (¹³C NMR). It was found that the element silicon existed in the form of Si–O bond in the SiUFF, and the hydroxymethyl group cross-linked with the amino group to form methylene at the curing stage, while internal thermal conduction caused surface crosslinking density to exceed that of the fiber core. Optimal performance of SiUFF was achieved with 4 wt % Si-modifier addition, cured at 190°C for 30 min, exhibiting an elongation at break of 7.1%, a tensile strength reaching 389 MPa and a char yield of 30.01% at 1000°C, which represented significant improvements of 96, 92, and 14.2%, respectively compared to the unmodified urea–formaldehyde fiber.