CRYSTALLIZATION KINETICS OF ETHYLENE-PROPYLENE COPOLYMERS PREPARED BY LIVING COORDINATION POLYMERIZATION

In this paper,crystallization kinetics of a series of ethylene-propylene copolymers prepared by living polymerization coordination catalyzed by a fluorinated bis(phenoxyimine)Ti catalyst(FI-EP copolymers)was studied,and was compared with that of ethylene-propylene copolymers prepared by a conventional Ziegler-Natta catalyst(ZN-EP copolymers).It is found that,the Avrami exponent and the crystallization rate constant of the FI-EP and ZN-EP copolymer show similar dependence on crystallization temperature,but the FI-EP copolymers exhibit a larger Avrami exponent than corresponding ZN-EP copolymers at high crystallization temperature and at low propylene content level.The crystallization temperature,equilibrium melting temperature and crystallinity of the FI-EP copolymers decrease more rapidly with propylene content than those of the ZN-EP copolymers.This can be attributed to their different comonomer distributions and partially to the different molecular weight distributions at low propylene content level.