Some aspects of the crystallization of ethylene copolymers

This report presents a continuation of studies from these laboratories that have been concerned with the crystallization behavior of ethylene copolymers. More specifically a comparison is made between the thermodynamic properties of ethylene-norbornene copolymers with those of the 1-alkene copolymers. In addition a detailed comparison is made of the thermodynamic, tensile, morphological and structural properties and the overall crystallization kinetics between the ethylene-1-alkene copolymers that do or do not contain small concentrations of long-chain branches. Except for the crystallization kinetics, the crystallization properties have been found to be essentially the same for both types of copolymers. A correlation has also been developed between the lamellar and supermolecular structures, the chemical nature of the comonomer and its concentration. Supermolecular structures range from spherulitic to micellar, depending on both comonomer type and concentration. Analysis of the overall crystallization kinetics demonstrates that the interfacial free energies that govern nucleation are independent of the lamellar and superstructures that evolve. (C) 2000 Elsevier Science Ltd. All rights reserved.