High-vinyl polybutadiene rubber (HVBR) and solution-polymerized styrene-butadiene rubber (SSBR) can meet the requirements of high-performance tires due to their excellent wet skid resistance and lower rolling resistance. In this paper, the effects of the vinyl and phenyl groups and their contents on the vulcanization behavior, mechanical strength, fatigue resistance, heat resistance, and wear resistance of HVBR and SSBR were investigated, and the dynamic viscoelasticities of HVBR and SSBR vulcanizates with or without carbon black were explored by dynamic mechanical analysis (DMA). The experimental results showed that the vinyl groups contributed more to the wear resistance and fatigue resistance of vulcanizates than the phenyl groups, but the phenyl groups contributed more to the mechanical strength of the vulcanizates than the vinyl groups. The DMA results showed that the vinyl and phenyl groups could significantly improve the road-gripping capability and wet skid resistance of HVBR and SSBR vulcanizates, but carbon black could slightly weaken the effect of vinyl and phenyl groups on the wet skid resistance of vulcanizates, and the effect of carbon black on vinyl groups was more significant. Despite the presence of carbon black, the phenyl groups contributed more heat buildup to the vulcanizates than the vinyl groups.
Shape-memory polymers are important smart materials with potential applications in smart textiles, medical devices, and sensors. We prepared trans-1,4-polyisoprene, low-density polyethylene (LDPE), and high-density polyethylene (HDPE) shape-memory composites using a simple mechanical blend method. The mechanical, thermal, and shape-memory properties of the composites were studied. Our results showed that the shape-memory composites could memorize 3 temporary shapes, as revealed by the presence of broad melting transition peaks in the differential scanning calorimetry curves. In the trans-1,4-polyisoprene/LDPE/HDPE composites, the cross-linked network and the crystallization of the LDPE and HDPE portions can serve as fixed domains, and all crystallizations can act as reversible domains. We proposed a schematic diagram to explain the vital role of the cross-linked network and the crystallization in the shape-memory process.
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