Facile preparation of bimodal polyethylene with tunable molecular weight distribution from ethylene polymerization catalyzed by binary catalytic system in the presence of diethyl zinc

摘要

This contribution reported a facile approach to bimodal polyethylene (BMPE) with a consecutively tunable molecular weight distribution (MWD). The BMPEs were synthesized from ethylene polymerization catalyzed by α -diimine Ni complex/ rac -ethylenebis(indenyl) zirconium chloride (rac -Et(Ind)_2 ZrCl_2)/MAO in the presence of diethyl zinc (ZnEt_2). From GPC results, PE samples with molecular weight (MW) ranging from 78.9 kg/mol to 1.5 kg/mol and PDI varying gradually from 2.5 to 12.7 were obtained via simply adjusting the equiv. of ZnEt_2 . The combination of Soxhlet extraction and GPC analysis indicated that the obtained BMPEs consist of soluble fractions with higher molecular weights and residual fractions with lower molecular weights. The crystallization processes and crystal morphologies of the BMPEs were recorded by polarized optical microscope (POM). Additionally, the influence of the obtained BMPE on the mechanical properties of commercial high density polyethylene (HDPE) after melt blending was studied via dynamic mechanical analysis (DMA).