Measurement and mathematical modeling of molecular weight and chemical composition distributions of ethylene/-olefin copolymers synthesized with a heterogeneous Ziegler-Natta catalyst

Abstract

The distributions of molecular weight and chemical composition of two linear low-density poly-ethylene resins synthesized with Ziegler-Natta catalysts were analyzed with several microstructural characterization techniques and the results were used to investigate the nature of the active site types present on the catalyst. Deconvolution of the molecular weight distribution measured by gel permeation chromatography and of the chemical composition distribution measured by either crystallization analysis fractionation or temperature rising elution fractionation or temperature rising elution fractionation leads to consistent results that indicate the presence of multiple active site types on the catalyst. This shows that these fractionation techniques, when combined with adequate mathematical models, are powerful tools to understand the behavior of Ziegler-Natta catalysts and structural properties of the produced resins.