Photographic Light Scattering and Photomicroscopy of Deformed Ringed Spherulites

Polyethylene films were studied by photographic light scattering and photomicroscopy at successive increments of strain, usually 5%. Photomicrographs were taken at times sufficiently long after sample deformation so that the light scattering patterns were constant with respect to intensity and shape. Analysis of such scattering patterns and photomicrographs indicated that upon spherulite deformation, the ring spacing (hence the twist‐distance) increased in the direction of tensile strain and decreased at right angles to the strain direction, as noted in earlier experiments on samples subjected to tensile stress. At about 30% strain the wide‐angle parallel polarizer scattering pattern (polarization and strain directions horizontal) split into a set of 4 arcs nearly parallel to the meridian. With increasing strain (analyzer and strain directions vertical) the arcs of the 4‐arc wide‐angle crossed polarizer scattering pattern, originally at 45° to the polarizer and analyzer axes, occurred nearer the meridian and became nearly parallel to the equator. Photomicrographs indicated that at 30% strain the ring spacing at right angles to the strain direction was extremely small or in some cases not resolvable and that discontinuities occurred in the rings. Immediately adjacent to the axis of sample deformation in many spherulites there was a discontinuity in the rings such that they appeared to cross the axis at an angle of 50° to 60°. The relationship between the changes observed by light scattering and the changes observed by microscopy is shown. Photomicrographs and light scattering patterns are presented and a brief analysis of the changes is given in terms of mechanisms of spherulite deformation.