EFFECTS OF SURFACE CRYSTALLINITY ON DYNAMIC-MECHANICAL PROPERTIES OF COMPRESSION-MOLDED POLYPROPENE SHEETS

Dynamic mechanical properties are measured for a series of compression -molded polypropene sheets having the same bulk crystallinity but diff erent surface crystallinity. The temperature of the alpha-dispersion w as shifted to lower temperatures with lowering the surface crystallini ties of the sheets. A shoulder peak, which is ascribed to the surface layer, appeared between the alpha- and beta-dispersion for the sheets. In addition, the application of the Takayanagi model to the experimen tal results suggests the difference in the continuity of the amorphous phase between the surface layer and the bulk.