Morphology of polypropylene spherulites

Dendritic spherulites of polypropylene were investigated in detail with the optical microscope. Dendrites grow and form twisted spherulites, and the twisting direction is clockwise toward the growing fronts. Dendrites could imbibe small spherulites on their tips, which seem to be elemental units of dendrites, and there are many knots on each branch of dendrites. In crystallization on a free surface, the supercooled polymer molecules involved in crystallization migrate to the growing fronts, and the resultant spherulites have oval structure. The thickness of the oval is larger than that of the parent film. The radial growth rates of dendrite are discussed.