Chemical compositional distribution of ethylene-1-butene copolymer prepared with heterogeneous ziegler-natta catalyst: TREF and crystaf analysis

Ethylene-1-butene copolymers were prepared with SiO₂-supported TiC1₄ catalyst by changing of 1-butene/ethylene molar ratio in feed, and the resulting copolymers were analyzed using temperature rising elution fractionation (TREF) and crystallization fractionation (Crystaf) methods to investigate the influence of C₄/C₂ molar ratio in feed on chemical compositional distribution and other parameters such as molecular weight and its distribution. TREF analysis showed that the copolymers had a broad and bimodal chemical compositional distribution (CCD) regardless of the content of 1-butene in the copolymer. The chemical composition was in the range of 5 to 55 branches per 1,000 carbons for all copolymers prepared in the study. Furthermore, the broader CCD was revealed for the copolymers having the higher content of 1-butene. Crystaf analysis did not showed a bimodal CCD for the copolymers having the 1 -butene content of less than 5.1 wt%. The lower crystalline part having higher 1 -butene content in Crystaf analysis was less than that of TREF analysis.