Effect of the molecular architecture of graft copolymers on the phase morphology and tensile properties of PS/EVA blends

摘要

Graft copolymers of poly(ethylene-co-vinyl acetate) (EVA) grafted with polystyrene (PS) with different molecular weight and different EVA/PS ratio were prepared by coupling reaction between acyl chloride functionalized PS (PS-COCl) and hydrolyzed EVA. PS-COCI with controlled molecular weight was prepared by anionic polymerization of styrene, followed by end capping with phosgene. The effect of the molecular architecture of the graft copolymer on the compatibilization of PS/EVA blends was investigated. Substantial improvement in the elongation at break and ductility was observed using the graft copolymer with PS segments with molecular weight as high as 66,000 g/mol and with a PS proportion equal or higher than EVA. The effect of the compatibilization on the morphology was also investigated by scanning electron microscopy and atomic force microscopy. The blend that presented the highest value of elongation at break also displayed dispersed phase constituted by inclusions of the PS phase inside the EVA particle forming a cocontinuous structure, as observed by AFM. (C) 2007 Wiley Periodicals, Inc.