Bulk Crystallization Kinetics of Metallocene Polyethylenes with Well-controlled Molecular Weight and Short Chain Branch Content

Abstract

Collaborating with Phillips Petroleum Company, we obtained a series of metallocene polyethylenes (mPE) with narrow molecular weight distribution and uniform short chain branching. The overall crystallization data of these mPEs and two other linear PEs determined from differential scanning calorimetry (DSC) was analyzed and compared using the well-known Avrami equation. The crystallization temperature and the crystallization rate were found to depend on the molecular weight and short chain branch (SCB) content as well. However, the SCB content played a comparatively dominant role. The secondary-nucleation-theory-based regime transition concept was applied to analyze the kinetic data, too. The crystal growth regimes and the regime transition temperatures observed were discussed in terms of the effect of SCB on the relative rates of surface nucleation and lateral spreading.