Effect of crystallization temperature and propylene sequence length on the crystalline structure of propylene-ethylene random copolymers  

作　　者：GOU QingQiang LI HuiHui YU ZhenQiang CHEN ErQiang ZHANG YuDong YAN ShouKe 

机构地区：[1]Beijing National Laboratory for Molecular Sciences, and State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China [2]Department of Polymer Science, School of Chemistry, Peking University, Beijing 100871, China [3]Beijing Research Institute of Chemical Industry, SINOPEC, Beijing 100013, China [4]candidate of Graduate University of Chinese Academy of Sciences, Beijing100039, China

出　　处：《Chinese Science Bulletin》2008年第12期1804-1812,共9页

基　　金：the Outstanding Youth Fund of the National Natural Science Founda-tion of China (Grant No 20425414);National Natural Science Foundations of China (Grant Nos. 50521302, 20423003, 20574079,and 20604031);State "973" Pro-grams from the Ministry of Science and Technology of China (Grant No.2003CB615602)

摘　　要：Crystallization behavior and resultant crystalline structure of a series of temperature-rising elu-tion-fractionated specimen of a Ziegler-Natta catalyst-synthesized propylene-ethylene random co-polymer were studied by DSC, WAXD and AFM. The experimental results indicate that both crystalliza-tion temperature and propylene sequence length exhibit great influence on the crystallization behavior and crystalline structure of the copolymer. It was found that the ethylene co-monomers acting as point defects inserted into the polypropylene chains play an important role in the formation of γ-iPP. As the co-monomer content increases, the crystallizable sequence length of iPP decreases, which produces an appropriate condition for its γ crystallization. At the same time, the existence of chain defects leads to a lower crystallinity of the copolymer and imperfection of the resultant crystals. For each individual sample with certain propylene sequence length or ethylene content, the increment of γ-iPP crystal content with increasing crystallization temperature demonstrates that higher crystallization tempera-ture is in favor of the γ-iPP crystallization. Pure γ-iPP crystals have been got in samples with propylene sequence length lower than 21 under suitable crystallization conditions.Crystallization behavior and resultant crystalline structure of a series of temperature-rising elution-fractionated specimen of a Ziegler-Natta catalyst-synthesized propylene-ethylene random copolymer were studied by DSC, WAXD and AFM. The experimental results indicate that both crystallization temperature and propylene sequence length exhibit great influence on the crystallization behavior and crystalline structure of the copolymer. It was found that the ethylene co-monomers acting as point defects inserted into the polypropylene chains play an important role in the formation of y-iPP. As the co-monomer content increases, the crystallizable sequence length of iPP decreases, which produces an appropriate condition for its y crystallization. At the same time, the existence of chain defects leads to a lower crystallinity of the copolymer and imperfection of the resultant crystals. For each individual sample with certain propylene sequence length or ethylene content, the increment of y-iPP crystal content with increasing crystallization temperature demonstrates that higher crystallization temperature is in favor of the y-iPP crystallization. Pure y-iPP crystals have been got in samples with propylene sequence length lower than 21 under suitable crystallization conditions.

关 键 词：结晶 温度 晶体 乙烯 共聚物 

分 类 号：O632[理学—高分子化学]