Reduced filler flocculation in the silica-filled styrene–butadiene–glycidyl methacrylate terpolymer

Abstract

This study presents a method to improve the dispersion of silica in rubber compounds using a styrene-butadiene-glycidyl methacrylate terpolymer (GMA-SBR) synthesized by cold emulsion polymerization. It has been demonstrated that silica particles in conventional rubbers tend to agglomerate during storage, as well as at the onset of vulcanization, because of their polarity. GMA-SBR can improve the compatibility with silica by the formation of covalent bonds between the epoxy groups of GMA-SBR and silanol groups on the silica surface. SBR 1721 and GMA-SBR silica-filled compounds were prepared without curatives by a kneader and a two-roll mill. After compounding, the reaction of the epoxy group, filler flocculation, and morphology of the compounds were analyzed using infrared spectroscopy, a rubber process analyzer, and transmission electron microscopy, respectively. In addition, the content of bound rubber in the compounds was determined by extracting the unbound rubber material with toluene. The GMA-SBR silica-filled compounds had a higher bound rubber content and exhibited significantly different filler flocculation and silica dispersion behaviors compared with the SBR 1721 silica-filled compounds.