Surface structure of isotactic polypropylene by X‐ray diffraction

Abstract

AbstractWith the glazing angle incidence of an X‐ray beam, the surface structure of compression molded isotactic polypropylene film was investigated by X‐ray diffraction. A comparison of the crystallinities between the surface and the bulk was made for films annealed in air at different temperatures and times. The crystallinity was lower for the surface compared with the bulk irrespective of annealing conditions. A drastic change in crystallinity occurred up to depths of several micrometers from the surface, and crystallinity decreased near the surface. The apparent crystallite sizes were smaller for the surface. This showed that crystal growth was restricted near the surface because of localized defects (including chain ends), and high chain mobility. Annealing at higher temperatures induced surface oxidation, which also decreased the surface crystallinity. The residual stress near the surface, attributable to quenching from the melt, was also detected by this method.