INFLUENCE OF COPOLYMER COMPOSITION ON PHASE-STRUCTURE AND CRYSTALLIZATION OF POLY(ETHYLENE OXIDE) POLY(ETHYLENE-CO-VINYL ACETATE) BLENDS

The influence of copolymer composition and crystallization temperature on the kinetics of crystallization and the morphology of poly(ethylene oxide)/Poly(ethylene1-y-co-vinyl acetate(y)) 80/20 wt/wt blends was analysed. It was found that the morphology and the crystallization rate are strongly dependent on the copolymer composition, y (mole fraction). In particular, for blends containing the copolymer with low content of vinyl acetate (VAc) (y less-than-or-equal-to 0.43), the non-crystallizable material segregates into spherical domains in intraspherulitic regions. The spherulite growth rate G is slightly depressed and the overall crystallization rate is independent of the copolymer composition in the blends. For blends with high VAc content (y greater-than-or-equal-to 0.56), there is no evidence that the copolymer forms segregated domains. For these blends, G and the overall crystallization rate are markedly depressed with respect to that of the pure poly(ethylene oxide) (PEO). The results obtained were accounted for by assuming that the copolymers with y greater-than-or-equal-to 0.56 were miscible with the PEO, whereas those with y less-than-or-equal-to 0.43 formed a two-phase separated system with the PEO.