Self-Acceleration of Nucleation and Formation of Shish in Extension-Induced Crystallization with Strain Beyond Fracture

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• 作者：Kunpeng Cui ; Lingpu Meng ; Nan Tian ; Weiqing Zhou ; Yanping Liu ; Zhen Wang ; Jie He ; Liangbin Li
• 刊名：Macromolecules
• 出版年：2012
• 出版时间：July 10, 2012
• 年：2012
• 卷：45
• 期：13
• 页码：5477-5486
• 全文大小：532K
• 年卷期：v.45,no.13(July 10, 2012)
• ISSN：1520-5835

文摘

Extension flow induced crystallization of isotatic polypropylene (iPP) has been studied with a combination of extension rheological and in situ small-angle X-ray scattering (SAXS) measurements at 140 掳C. Rheological data of step extension on iPP melt are divided into before and beyond fracture strain zones in strain鈥搒train rate space, where intermediate strains between them lead to fracture of samples. Coincidently, weak and strong accelerations of nucleation are observed in the before and beyond fracture strain zones respectively, where distinctly different features of crystallization kinetics and nucleation form occur in these two zones. The microrheological model explains the acceleration of nucleation in the 鈥渂efore fracture strain zone鈥?well, while a 鈥済host nucleation鈥?mechanism is proposed to interpret the strong acceleration of nucleation in the 鈥渂eyond fracture strain zone鈥? The 鈥済host nucleation鈥?is due to the displacement of initial parent point nuclei, where daughter nuclei are induced along the trails. This new mechanism explains well the acceleration of nucleation in orders of magnitude and the formation of shish in iPP melt.