Self-nucleation and heterogeneous nucleation in ethylene/1-octene random copolymer and its linear polyethylene blends

Abstract

Self-nucleation normally denotes an increase in the crystallization temperature during cooling down from certain preheated (seeding) temperature due to the existence of unmolten crystalline nuclei or some heterogenous structures which can induce melt memory effect. It is one of the crucial parts in the study of polymer crystallization behavior which provides a meaningful guidance in both academia and industry to accelerate crystallization of polymers. In this work, self-nucleation effects of a commercial ethylene/1-octene random copolymer with 12 mol% 1-octene content and its blends with small amount of linear polyethylene (LPE) were investigated. The ethylene/1-octene random copolymer possesses strong self-nucleation effect whereas in the blends the crystallization temperature increases with the seeding temperature and eventually stabilized at certain constant temperature when the seeding temperature is high enough. This result is clearly due to the heterogenous nuclei generated by the crystallization of LPE during cooling. The strength of the heterogenous nucleation effect i.e. the crystallization temperature is positively related to the degree of dispersion of LPE in the mixture.