Effect of short chain-branching distribution on crystallinity and modulus of metallocene-based ethylene-butene copolymers

摘要

In this article, the short chain-branching distribution (SCBD) of some metallocene-based ethylene-butene copolymers was evaluated by DSC, and some conventional ethylene copolymers were also studied for the purpose of comparison. It is found that metallocene-based ethylene copolymers have a relative narrower SCBD. These copolymers were crystallized under different modes, and the crystallinity and initial modulus of them were examined. The metallocene-based ethylene copolymers contain less interfacial regions, and the melting temperatures of them decrease more rapidly with the decrease of density than those of conventional ethylene copolymers. Moreover, the metallocene-based and conventional ethylene copolymers of similar density have close initial modulus when they are quenched or annealed at 100 degrees C, but conventional ethylene copolymers show higher initial modulus when stepwise crystallized from 120 degrees C. These differences in crystallinity and initial modulus were explained based on their differences in short-chain branching distributions. (C) 2000 John Wiley & Sons, Inc. [References: 31]