title: Extensional Flow-Induced Dynamic Phase Transitions in Isotactic Polypropylene.
abstract: With a combination of fast extension rheometer and in situ synchrotron radiation ultra-fast small- and wide-angle X-ray scattering, flow-induced crystallization (FIC) of isotactic polypropylene (iPP) is studied at temperatures below and above the melting point of α crystals (Tmα). A flow phase diagram of iPP is constructed in strain rate-temperature space, composing of melt, non-crystalline shish, α and α&β coexistence regions, based on which the kinetic and dynamic competitions among these four phases are discussed. Above Tmα , imposing strong flow reverses thermodynamic stabilities of the disordered melt and the ordered phases, leading to the occurrence of FIC of β and α crystals as a dynamic phase transition. Either increasing temperature or stain rate favors the competiveness of the metastable β over the stable α crystals, which is attributed to kinetic rate rather than thermodynamic stability. The violent competitions among four phases near the boundary of crystal-melt may frustrate crystallization and result in the non-crystalline shish winning out.
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Jianzhu
authors.initials: J
authors.lastname: Ju
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wang
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Fengmei
authors.initials: F
authors.lastname: Su
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China. yxji@mail.ustc.edu.cn.
authors.forename: Youxin
authors.initials: Y
authors.lastname: Ji
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Haoran
authors.initials: H
authors.lastname: Yang
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Jiarui
authors.initials: J
authors.lastname: Chang
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Sarmad
authors.initials: S
authors.lastname: Ali
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Li
authors.affiliation: National Synchrotron Radiation Lab, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, 230029, China. lbli@ustc.edu.cn.
authors.forename: Liangbin
authors.initials: L
authors.lastname: Li
mesh_terms: D003460:Crystallization; D007700:Kinetics; D044367:Phase Transition; D011126:Polypropylenes / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D011126:Polypropylenes
keywords: crystallization; melt; polypropylene; real-time X-ray scattering