THE EFFECT OF CATALYST ON INTERMOLECULAR HETEROGENEITY DISTRIBUTION IN ETHYLENE/1-HEXENE COPOLYMERS

Białek M., Czaja K., Sacher B.

University of Opole, Institute of Chemistry

Copolymers of ethylene with higher 1-olefins are important class of polymer products due to their specific properties. Ethylene/a-olefin copolymers properties depends not only on the type and amount of the a-olefin comonomer in the polymer but also on its distribution along the polymer chain [1]. Measurement of the comonomer distribution in branched polyethylene has mostly been performed using Differential Scanning Calorimetry (DSC). In our study, successive self-nucleation/annealing (SSA) procedure has been applied for fractionation of ethylene/1-hexene copolymers synthesized with supported vanadium and zirconocene catalysts.

It was found that the copolymers obtained over all catalytic systems gave thermograms resolved into several peaks but they differ each from other the number of peaks and melting points. The amounts of copolymer fraction with defined lamellar thicknes using the Thomson-Gibbs equation have also been determined. It have been obtained that the copolymer produced from the metallocene system contains a thinner and more homogeneous lamella thickness than that obtained with Ziegler-Natta vanadium catalyst.

[1] Müller A. J., Hernández Z. H., Arnal M. L., Sánchez J. J., Polym. Bull. 39 (1997), 465