CORRELATION OF PROPERTIES WITH STRUCTURE IN ZIEGLER POLYPROPYLENES

Isotactic polypropylenes, varying in molecular weight, crystallinity, and tacticity, were characterized by spectroscopic and chromatographic techniques in order to obtain suitable samples for investigating the effect of structure on properties. Mechanical and thermal properties were studied with respect to their structural dependence. Melting points and rates of crystallization were observed to be higher in the more stereoregular samples, while evidence of fractionation by molecular weight and tacticity was observed in less stereoregular samples. Tensile properties displayed marked dependence on polymer stereoregularity, while examination of fractured surfaces by microscopy showed that fracture occurred at regions of high impurity concentration.