Strain Hardening in Uniaxial Elongation vs. Temperature for Random Copolymer Melts with High Comonomer Content

Two metallocene-catalyzed random copolymers with a polyethylene backbone and octene comonomer content of 20 wt% and 38 wt% were tested in uniaxial extensional flow at different temperatures. Sparse LCB was detected in both melts with these measurements. The strain hardening parameter at the lowest strain rate was found to be greater for EO3, the material with the smaller degree of LCB. The temperature dependence of the strain hardening parameter was also greater for EO3 than for EO1. These trends may be related to the two model parameters used by Wagner and coworkers representing branch content and the maximum tube diameter contraction.