Mechanical Properties of Styrene-Butadiene Block Copolymer Grafted with Methacrylic Esters or Acrylic Esters

The modification of styrene-butadiene block copolymer (SBS) was carried out by the graft polymerization of various methacrylic esters or acrylic esters. The effects of degree of grafting, glass trandition temperature (Tg) of the polymer of graft chain, morphology on mechanical properties of the resulting graft polymers were investigated. The graft polymers having the graft chain of high Tg had better tensile and tear properties. The graft polymers with methyl methacrylate had extremely high tensile strength and modulus at low degree of grafting (about 5%). From dynamic viscoelastic behavior patterns, it was found that the graft chain was compatible with polystyrene segment at low degree of grafting, or in the case of graft chain having low Tg and similar solubility parameter as that of polystyrene. The microdomain structure of graft polymers and the ratio of surface area of polystyrene domain differed with cast solvents, but tensile strength was almost constant. These results confirmed that the graft polymers had high tensile strength and modulus because the graft chain and polystyrene segment were compatible and had a phycical crosslinkage at low degrees of grafting.