Equilibrium Melting Temperatures of Ethylene Copolymers: An Appraisal of the Applicability of the Flory and Sanchez-Eby Approaches

Abstract

The equilibrium melting temperatures of linear polyethylenes and ethylene/1-octene random copolymers were determined as a function of molecular weight and branch content. This systematic study makes it possible to evaluate two equilibrium melting temperature depression equations for the olefin type random copolymers, the Flory equation, and the Sanchez-Eby equation, as a function of defect content and molecular weight. An empirical equation suggested in this study for predicting the equilibrium melting point of linear polyethylene as a function of molecular weight is more sensitive to molecular weight than the Flory-Vrij equation. The range over which the two equations can be applied depends on the defect content, after molecular weight correction. This chapter explains how the MW dependence on T°m of linear polyethylene is determined and how it does not correspond to the Flory-Vrij equation. An empirical Eq 1 is more sensitive to MW than the Flory-Vrij equation.