An X-ray method for determination of crystallinity as a function of depth from a polymer surface

摘要

Manufactured articles of semicrystalline polymers usually have a variation in texture (degree of crystallinity and crystal orientation) as a function of the depth from the external surface. This is often due to the fact that the crystallization process near the surfaces occurs at different conditions and rates relative to the bulk of the material. In this report we present an X-ray diffraction technique to elucidate the changes in the degree of crystallinity as a function of depth from the surface. Changes in the scheme of x-ray diffractometer (reflection or transmission, slit width, etc.), the linear material absorption coefficient (using different wavelengths) and the diffraction angle have different effects on the scattering from layers at different depths. It is thus possible to define the material heterogeneity as a function of depth. This method is demonstrated using a film of vinylidene fluoride-tetrafluoroethylene (5 mol%) copolymer that has been crystallized asymmetrically by quenching on one side. The increase in crystallinity from a negligible value on the quenched side to the bulk value is presented.