TIME-RESOLVED SIMULTANEOUS SMALL-ANGLE AND WIDE-ANGLE X-RAY-SCATTERING DURING POLYETHYLENE DEFORMATION .1. COLD DRAWING OF ETHYLENE-ALPHA-OLEFIN COPOLYMERS

The cold drawing behaviour of a range of polyethylene copolymers was i nvestigated using the technique of simultaneous small-and wide-angle X -ray scattering (SAXS and WAXS, respectively) during deformation. The influence of branch amount, branch length and lamellar population were studied. Branch length was found to be unimportant. Increasing branch content lowered the percentage crystallinity which resulted in an inc rease in the importance of interlamellar deformation mechanisms. Doubl e yield points were observed in some samples. Molecular and lamellar d eformation was totally reversible up to the first yield point, and was apportioned to the activation of fine chain slip. After the second yi eld point, for which coarse chain slip leading to lamellar fragmentati on was held responsible, deformation was irreversible. (C) 1997 Elsevi er Science Ltd.