Abstract: The microstructure of a-iPP films prepared by solution-casting on glycerol and crystal-lized at different temperature was investigated by means of defocused electron microscopy andelectron diffraction techniques. Microscopic observation showed that all the samples consis-ted of two kinds of structures: cross-hatched and single-crystal-type structure, independentof crystallization temperature. In the cross-hatched structure, as a result of epitaxial cry-stallization, there existed wide-angle and low-angle branchings of lamellae seen edge-on.The characteristics of the former branching were accounted for by the way of epitaxial growth of daughter lamellae on the lateral face(010)of parent lamellae substrate, while thelater was explained in this paper by the theory of branching of individual dominant lamel-lae proposed by Bassett and Olley.

Key words: polypropylene, morphological structate, epitaxial crystallization