In situ polymerization and properties of methyl methacrylate-butadiene-styrene resin with bimodal rubber particle size distribution

The in situ polymerization synthesis and properties of methyl methacrylate-butadiene-styrene resin (MBS resin) with bimodal rubber particle size distribution were investigated. MBS resin was prepared by bulk-suspension polymerization of styrene and methyl methacrylate in the presence of the styrene-butadiene block copolymer, and bimodal rubber particle size distribution was observed during bulk polymerization and cooling. During bulk polymerization and cooling. size distribution was regulated by the viscosity of the prepolymer or shearing for the prepolymer. The formative mechanisms of the bimodal distribution were presumed to be increase of small rubber particles by shearing and delay in changing to small rubber particles according to the difference in the inside structure of large rubber particles. MBS resin with the bimodal distribution was obtained by suspension polymerization using the prepolymer with bimodal distribution. The resin was superior with regard to balance of impact resistance and transparency.