RHEOLOGICAL AND MECHANICAL-PROPERTIES OF STYRENE-BUTADIENE RUBBER COMPOUNDS CONTAINING RUBBER POWDER VULCANIZATES

The cure behavior, rheological property, and tensile strength of styre ne-butadiene rubber (SBR) compounds containing different sizes of rubb er powder vulcanizates (RPV) were investigated by varying the loading from 0 to 40 phr. Six different sizes of RPV were selected to see the effect of particle size. A typical reclaimed rubber powder was also us ed to see the reclaiming effect. The average particle size of the RPVs ranged from 70 to 2,000 mu m. In the cure characteristics, as the pow der loading was increased, the maximum torque, scorch time, and optimu m cure time decreased, while minimum torque increased. At lower shear stresses (or shear strains) the viscosity of the rubber compounds incr eased noticeably with the addition of RPV. This increase was diminishe d at higher shear stresses. However, the die swell decreased when RPV was added. With increased powder loading the tensile strength decrease d dramatically at lower powder concentrations, similar to 10 phr, and then the rate of this decrease became slower at higher concentrations. A power-law relation was observed between the tensile strength reduct ion and the particle size of the RPV.