Deformation mechanisms in biaxially drawn polyethylene

The crystal orientation of solid‐state biaxially drawn solution‐crystallized ultra‐high‐molecular weight polyethylene (UHMW‐PE) film has been revealed from flat‐plate wide‐angle x‐ray scattering (WAXS) patterns and interpreted in terms of crystal plasticity. A slightly drawn film (λ ≤ 3 × 3) possesses only a (100) planar orientation, whereas in a highly drawn film (λ ≥ 6 × 6), a mixed (100) and {110} planar orientation is present. Crystal deformation is found to proceed both by slip on (100) and {110} planes, resulting in a (100) texture in a similar way to crystal deformation in uniaxially drawn polyethylene and by {110} 〈110〉 transverse slip and/or {310} twinning which results in a {110} texture. It is postulated that during transverse slip or twinning, the molecules deform without chain extension. As a consequence, neither the molecular draw ratio nor the tensile properties change significantly for macroscopic draw ratios above 10 in contrast to the data obtained for uniaxially drawn polyethylene.