超临界聚合法等规聚丙烯的结晶行为

采用差示扫描量热法及带热台在线偏光显微镜直接观察法，研究了超临界聚合与常规淤浆聚合这两种不同聚合工艺所制备等规聚丙烯的等温结晶行为.结果表明，超临界法聚丙烯（sc-iPP）由于其较低的分子量及较窄的分布，使得等温结晶速率比常规淤浆法聚丙烯（c-iPP）快，结晶度高，且sc-iPP的晶体呈负光性，倾向于异相成核.而c-iPP的晶体则呈混光性，倾向于均相成核，但两者均为典型的球晶，均体现热成核机理.

STUDY ON CRYSTALLIZATION BEHAVIOR OF ISOTACTIC POLYPROPYLENE PRODUCED BY SUPERCRITICAL POLYMERIZATION

The isotactic polypropylene prepared under the supercritical conditions was compared with that obtained by a conventional slurry polymerization with respect to the isothermal crystallization kinetics by Perkin Elmer differential scanning calorimetry(DSC) and Nikon E600 optical polarimeter(OP) with on-line hot stage,respectively.The results indicate that isothermal crystal radius growth rate of supercritical isotactic polypropylene(sc-iPP) with lower molecular weight and narrower its distribution is faster than that of common isotactic polypropylene(c-iPP).Moreover,crystallinity of sc-iPP is higher than that of c-iPP.The resulting crystals of sc-iPP have negative character and tend heterogeneous nucleation.On the contrary,the obtained crystals of c-iPP present heterozygosis birefringence and prefer homogeneous nucleation.Furthermore,Both sc-iPP and c-iPP are spherulites and show thermal nucleation.Base on these,crystallization activity energy and Avrami exponent of both sc-iPP and c-iPP were calculated,respectively.