Particle size distribution, mixing behavior, and mechanical properties of carbon black (high-abrasion furnace)-filled powdered styrene butadiene rubber

High-abrasion furnace black (HAF, grade N330)-filled powdered styrene butadiene rubber [P(SBR/HAF)] was prepared and the particle size distribution, mixing behavior in a laboratory mixer, and mechanical properties of P(SBR/HAF) were studied. A carbon black-rubber latex coagulation method was developed for preparing carbon black-filled free-flowing, noncontact staining SBR powders, with particle diameter less than 0.9 mm, under the following conditions: carbon black content > 40 phr, emulsifier/carbon black ratio > 0.02, and coating resin content > 2.5 phr. Over the experimental range, the mixing torque T. of P(SBR/HAF) was not as sensitive to carbon black content and mixing temperature as that of HAF-filled bale SBR (SBR/HAF), whereas the temperature build-up AT showed little dependency on carbon black content. Compared with SBR/HAF, P(SBR/HAF) showed a 20-30% mixing energy reduction with high carbon black content (>30 phr), which confers to powdered SBR good prospects for internal mixing. Carbon black and the rubber matrix formed a macroscopic homogenization in P(SBR/HAF), and the incorporation step is not obvious in the internal mixing processing results in these special mixing behaviors of P(SBR/HAF). A novel mixing model of carbon black-filled powdered rubber, during the mixing process in an internal mixer, was proposed based on the special mixing behaviors. P(SBR/HAF) vulcanizate showed better mechanical properties than those of SBR/HAF, dependent primarily on the absence of free carbon black and a fine dispersion of filler on the rubber matrix attributed to the proper preparation conditions of noncontact staining carbon black-filled powdered SBR. (C) 2004 Wiley Periodicals, Inc.