Study of the cure characteristics and viscoelastic behavior of styrene-butadiene rubber compounds by using a rubber process analyzer

Viscoelastic and cure properties of styrene‐butadiene rubber compounds were investigated by using a “Rubber Process Analyzer.” The effects of sulfur content in the cure system and carbon black (CB) type and concentration on the cure behavior of samples were studied. As the ratio of S/accelerator in the curative increased, the cure rate increased, and the cure time decreased. Here, the elasticity was analyzed by considering the drop in the maximum of viscous torque ( D S″ ) and the resilience, which increased for the cure systems in the order of conventional < semiefficient < efficient. Compounds with the higher loading and fine particle size of CB had the greater cure torque values, higher vulcanization rates, and the lower cure times. With increasing CB content and CB specific surface area, D S″ diminished, hence the elasticity. The Payne effect was observed in all strain‐sweep curves. At higher level and surface area of CB, the linear viscoelastic region disappeared, and the strain dependency of G ′ was more pronounced. For higher loading and smaller particle size of CB, the relaxation modulus declined rather abruptly, and relaxation time increased. These observations signified more viscous and less elastic responses in these samples. Viscoelastic properties of compounds were explained by considering the hydrodynamic and dilution effects. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers