MICROSTRUCTURAL CHARACTERIZATION OF POLYPROPENE SURFACES USING GRAZING-INCIDENCE X-RAY-DIFFRACTION

The grazing incidence X-ray diffraction was applied for characterizing the crystalline structure of the outermost layer of polypropene sheet s. Even in the outermost surface layer within about 5 nm, the crystall ine structure of the a form was confirmed by the X-ray diffraction pat terns. The values of a and c for the crystal lattice dimension were al most constant in spite of the variation of surface layer crystallinity , whereas the value of b for the surface layer decreased with increasi ng crystallinity or decreasing comonomer content of polypropene. This suggests that the density of the crystal increased as a function of cr ystallinity. Additionally, the value of b for the surface layer was sm aller than that of the bulk. It was concluded that the lattice distort ion can be ascribed to the residual stress caused by the molding press ure under the higher supercooling rate.