Proton Magnetic Resonance and X-Ray Diffraction Studies of Polypropylene

Abstract

Crystallization and glass transition in various samples of polypropylene, have been studied by proton magnetic resonance over the wide temperature range −180∼200°C, and by X-ray diffraction at room temperature. It was found that the free rotation of methyl groups would be hindered below −130°C and the second moment tended to increase towards the rigid state value. Motional narrowing occurs gradually at −40°C in atactic polymer which is mostly amorphous. On the other hand, isotactic polymer which is highly crystalline, showed rather sharp narrowing from −10°C to 30°C, but the condition of heat treatment affected the behaviors of narrowing. X-ray diffraction patterns suggest that quenched film has smaller size of crystallite than that of annealed film. The line shape of atactic polymer is very similar to that of amorphous component decomposed by Wilson-Pake method in isotactic polymer, and then the degree of crystallinity of highly crystalline isotactic sample was estimated about 70∼80% at room temperature. When the isotactic polymer was cooled down from 200°C, recovery of crystallization was observed between 140 and 120°C.