A SMALL-ANGLE X-RAY-SCATTERING STUDY OF HIGH-DENSITY POLYETHYLENE ANDULTRAHIGH MOLECULAR-WEIGHT POLYETHYLENE

Small-angle X-ray scattering was used to compare the morphology of ext ruded ultrahigh molecular weight polyethylene (UHMWPE) and melt-crysta llized high-density polyethylene (HDPE). The crystalline morphology of UHMWPE has a low degree of order, rendering direct methods of analysi s of the scattering curves unsuitable. We have demonstrated that the i ndirect transformation method, requiring no extrapolation of the scatt ering curve, can be used to obtain the one-dimensional correlation fun ctions for these dense lamellar systems. The lamellar morphology of UH MWPE contained a large distribution of lamellar thicknesses, diffuse i nterfaces, and a large variation of interlamellar spacing as compared to those features in HDPE. The interlamellar spacing of extruded UHMWP E determined from the one-dimensional correlation function was 50 nm a nd that of melt-crystallized HDPE was 26 nm. The amorphous zone thickn ess of HDPE was 8 nm.