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The covulcanization characteristics, mechanical properties, compatibility, and hot-air aging resistance of hydrogenated nitrile-butadiene rubber (HNBR)/ethylene-propylene-diene rubber (EPDM) blends cured with either sulfur or dicumyl peroxide (DCP) were studied. The difference between M H and M L (M H À M L ), rheometer graphs, selective swelling and a dynamic mechanical analysis of HNBR/EPDM blends confirmed that the peroxide curing system gives better covulcanization characteristics than the sulfur curing system and peroxide exhibited higher crosslink efficiency on EPDM while sulfur showed larger crosslink efficiency on HNBR. Dynamic mechanical analysis and morphology indicated that the compatibility between HNBR and EPDM is limited. Tensile strength and elongation at break of the sulfur-cured blends are greater than those obtained with peroxide and increase with the HNBR fraction. The blends crosslinked with peroxide retain their tensile strength but not their elongation at break after hot air ageing better than blends vulcanized by sulfur.

The mechanical and damping properties of blends of ethylene-vinyl acetate rubber(VA content >40 wt %) (EVM)/nitrile butadiene rubber (NBR) and EVM/ethylene-propylene-diene copolymer (EPDM), both with 1.4 phr BIPB (bis (tert-butyl peroxy isopropyl) benzene) as curing agent, were investigated by DMA. The effect of polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and dicumyl peroxide (DCP) on the damping and mechanical properties of both rubber blends were studied. The results showed that in EVM/EPDM/PVC blends, EPDM was immiscible with EVM and could not expand the damping range of EVM at low temperature. PVC was miscible with EVM and dramatically improved the damping property of EVM at high temperature while keeping good mechanical performance. In EVM/NBR/PVC blends, PVC was partially miscible with EVM/NBR blends and remarkably widened the effective damping temperature range from 41.1 C for EVM/NBR to 62.4 C, while CPVC mixed EVM/NBR blends had an expanded effective damping temperature range of 63.5 C with only one damping peak. Curing agents BIPB and DCP had a similar influence on EVM/EPDM blends. DCP, however, dramatically raised the height of tan d peak of EVM/NBR ¼ 80/ 20 and expanded its effective damping temperature range to 64.9 C.

The mechanical and damping properties of blends of ethylene-vinyl acetate rubber (VA content > 40% wt) (EVM)/acrylonitrile butadiene rubber (NBR), with 1.4 phr BIPB [bis (tert-butyl peroxy isopropyl) benzene] as curing agent, were investigated by DMA and DSC. The effect of chlorinated polyvinyl chloride (CPVC), silica, carbon black, and phenolic resin (PF) as a substitute curing agent, on the damping and mechanical properties of EVM/NBR blends were studied. The results showed that 10 phr CPVC did not contribute to the damping of EVM700/NBR blends; Silica could dramatically improve the damping of EVM700/NBR blends because of the formation of bound rubber between EVM700/NBR and silica, which appeared as a shoulder tan d peak between 20 and 70 C proved by DMA and DSC. This shoulder tan d peak increased as the increase of the content of EVM in EVM/NBR blends. The tensile strength, modulus at 100% and tear strength of the blend with SiO 2 increased while the elongation at break and hardness decreased comparing with the blend with CB. PF, partly replacing BIPB as the curing agent, could significantly improve the damping of EVM700/NBR to have an effective damping temperature range of over 100 C and reasonable mechanical properties. Among EVM600, EVM700, and EVM800/NBR/ silica blend system, EVM800/NBR/silica blend had the best damping properties. The EVM700/NBR ¼ 80/10 blend had a better damping property than EVM700/NBR ¼ 70/20.