Effect of liquid isoprene rubber on dynamic mechanical properties of emulsionpolymerized styrene/butadiene rubber vulcanizates

The effect of liquid isoprene rubber (LIR) on the dynamic mechanical properties of emulsion-polymerized styrene/butadiene rubber (ESBR) vulcanizates was investigated by temperature sweep using dynamic mechanical analysis. The introduction of LIR led to ESBR vulcanizates having higher loss factor (tan d) in the temperature range - 30 to 0 degrees C, and lower tan d in the range 60 to 80 degrees C. A small amount of LIR-403 (LIR with carboxyl groups) led to a significant change in tan d: the addition of LIR-403 (3 phr) led to a 7.5% increase in tan d from - 30 to 0 degrees C, and a 24.9% decrease in tan d from 60 to 80 degrees C. It was found that the introduction of LIR increased the bound rubber content in the ESBR compound. Equilibrium swelling experiments showed that the crosslink density of the vulcanizates increased after the introduction of LIR-403 or LIR-50 (general purpose LIR). The change in tan d from 60 to 80 degrees C was related to polymerfiller interactions. The characteristic constant of fillerESBR matrix interaction (m) was calculated. At a given filler volume fraction, the increase in m in the presence of LIR could be well related to the decrease in tan d from 60 to 80 degrees C. The influence of LIR on filler network in the ESBR compound was also investigated by strain and temperature sweeps using a rubber processing analyzer. Copyright (C) 2011 Society of Chemical Industry