The dynamic mechanical behaviour of oriented ethylene-hexene-1 copolymer

A study has been made of the structure and dynamic mechanical properties of a highly oriented ethylene-hexene-1 copolymer. Samples were prepared by tensile drawing, and by drawing followed by annealing at either constant length or unconstrained. Following previous investigations on oriented polyethylene homopolymers, the −50°C plateau moduli were determined, together with estimations of the degree of crystal continuity obtained from X-ray diffraction measurements. Although general correlations were observed between the plateau moduli and the average crystal lengths, our previous intercrystalline bridge model cannot successfully model both homopolymer and copolymer data and it is concluded that for these copolymers there is a contribution to the mechanical moduli from the presence of oriented taut tie molecules as well as crystalline bridges.