丙烯超临界聚合中原生晶特征

通过广角X射线衍射(WAXD)对由丙烯超临界聚合和传统本体淤浆法制得的等规聚丙烯原生结晶特征进行了研究,并讨论了聚合工艺、预聚温度、粒径、分子量等对原生晶特征的影响。结果表明,超临界聚合法制备的等规聚丙烯(SC-iPP)呈现出α和γ的混合晶型,而采用传统淤浆法制备的等规聚丙烯(C-iPP)只含有单一α晶型,这是因为超临界的高温高压状态,使得体系传热传质阻力较小,更有利于原生晶型的发展。此外,预聚温度、粒径、分子量等因素也对丙烯超临界聚合所制得的SC-iPP结晶特征有显著影响。

Crystallographic behavior of nascent isotactic polypropylene produced under supercritical conditions

The materials used here were isotactic polypropylene (iPP) produced by conventional slurry polymerization and under supercritical conditions.Wide-angle X-ray diffraction (WAXD) patterns of the iPPs obtained under various conditions were recorded to analyze the nascent polymorphic form.The effects of polymerization process, pre-polymerization temperature,particle size and molecular weight of the resultant iPPs on nascent polymorphic form were investigated.The iPP produced by supercritical polymerization was the mixture of α and γ forms while the iPP produced by conventional slurry process was only in the α form, just because, in the supercritical state of high pressure and high temperature, mass and heat transfer should be faster, which would facilitate development of nascent polymorphic form. Furthermore, pre-polymerization temperature, particle size and molecular weight of obtained iPPs were found to have significant effect on nascent crystallographic behavior.