用SPEX冷冻研磨机研究研磨等规聚丙烯在低温研磨下之不可逆转的结构变化

Abstract The influence of cryogenic mechanical milling on the structure and the thermal behavior of isotactic polypropylene was investigated by means of wide-angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. The results presented show that structural changes caused by mechanical milling at cryogenic temperatures are only partly reversible. The decrease in the degree of crystallinity as determined by differential scanning calorimetry with increasing milling time is attributed to a reversible transformation of the initial morphology into a ‘‘nanostructured’’ morphology, consisting of small ‘‘fragments’’ of the original isotactic polypropylene lamellae. During recrystallization from the molten state, there still exists an influence of the previous milling treatment, leading to significantly changed crystallization behavior. The reason for this behavior might be a decrease in the molecular weight or a change in the molecular weight distribution or the formation of long-chain branched polypropylene molecules induced by cryogenic mechanical milling. Keywords Cryogenic mechanical milling Æ Polypropylene Æ Transmission electron microscopy Æ Nanostructure Æ Differential scanning calorimetry