Morphology of cold-drawn polyethylene

Small-angle studies suggest the presence of either a 1000- or a 100-Å periodicity in cold-drawn polyethylene. A 1000-Å periodicity is shown in cold-drawn polyethylene thin films to be due to regular placements of portions of two or three lamellae which stayed together during deformation by interlamellar ties. The 100-Å periodicity is shown by dark-field electron microscopy and, in particular, by bright-field diffraction-contrast microscopy to be due to alternating crystalline and noncrystalline units aligned in 100-Å diameter microfibrils. At lower draw ratios, a lateral alignment of the 100-Å units is observed, resulting in the formation of “wavy lamellae.” Although the wavy lamellae are destroyed at higher draw ratios, the 100-Å units remain present throughout the sample. These observations suggest the possible presence of a grain structure of the order of 100 Å in the original crystal.