Nonequilibrium Nature of Flow-Induced Nucleation in Isotactic Polypropylene

Cui, Kunpeng; Liu, Dong; Ji, Youxin; Huang, Ningdong; Ma, Zhe; Wang, Zhen; Lv, Fei; Yang, Haoran; Li, Liangbin

doi:10.1021/ma502412y

Cited by 66 publications

(63 citation statements)

References 40 publications

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“…When the flow is sufficiently strong, anisotropic morphology may be observed, for example, shish‐kebab or fibril‐like structure . Scenarios of a critical shear rate, strain, shear stress, or specific work have been proposed for shish‐kebab formation.…”

Section: Introductionmentioning

confidence: 99%

Exploring the polymorphic behavior of a β‐nucleated propylene‐ethylene random copolymer under shear flow

Zhang

Liu

Zhao

et al. 2020

Polymer Crystallization

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Shear flow strongly affects the polymorphism and crystallization kinetics of semicrystalline polymers. In the present work, the crystallization behavior of a β-nucleated propylene-ethylene (P-E) random copolymer was studied both under quiescent and shear flow by using in-situ wide-angle X-ray diffraction. It was observed that shear flow could shorten the induction time, fasten the crystallization rate and increase the degree of crystallinity. The populations of different crystal modifications varied significantly upon shearing. Especially the β crystals fraction decreased with shear strain.When the shear strain was higher than 100 with a fixed shear rate of 5 s −1 , the β crystals almost disappeared. Meanwhile, both the fractions and the crystallization rates of α and γ crystals were enhanced by shear flow. The complicated polymorphic behavior can be interpreted by the nucleation kinetics.

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Section: Introductionmentioning

confidence: 99%

Exploring the polymorphic behavior of a β‐nucleated propylene‐ethylene random copolymer under shear flow

Zhang

Liu

Zhao

et al. 2020

Polymer Crystallization

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“…Li et al studied the relationship between the formation of iPP helices and the crystallization of α‐iPP via in‐situ WAXD and FT‐IR. They proposed that iPP helices could form first, then the helices pack together and the interchain order is formed . However, this mechanism cannot explain the separation of the chiral chains when iPP crystallizes into β‐iPP.…”

Section: Resultsmentioning

confidence: 99%

Probing into the epitaxial crystallization of β form isotactic polypropylene: From experimental observations to molecular mechanics computation

Wang

Yang

Liu

et al. 2017

J Polym Sci B Polym Phys

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Compared with the most stable crystalline form of isotactic polypropylene (α‐iPP), β‐iPP shows superior impact strength and high temperature performance, though the mechanism of how the frustrated structure of β‐iPP is formed still remains unclear. In present work, the single crystal structure of a traditional β‐iPP nucleating agent, N,N′‐dicyclohexylterephthalamide (DCHT), was obtained for the first time and correlated with the epitaxial crystallization of β‐iPP on the surface of DCHT crystal. The combination of synchrotron radiation X‐ray microdiffraction and molecular chain packing model confirmed that a two dimensional match of chain‐axis and inter‐chain direction coexists between β‐iPP (110) plane and DCHT (001) plane. It was further found that an epitaxial model is helpful to understand the formation of the frustrated structure of 31 helices packing in β‐iPP. The molecular mechanics computation showed that as the (001) plane of DCHT is fixed, the packing mode of β‐iPP (110) plane on the substrate surface is more stable than that of α‐iPP (010) plane. This work clarifies the epitaxial crystallization mechanism of β‐iPP on DCHT by employing both experimental and computational evidences. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 418–424

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“…The pre-stretch method used in PA hydrogels in this study shares analogy to the mechanical stimuli approach used in metalworking 28,29 or semicrystalline polymer processing 30,31 , which is actually stress or strain induced molecular/atom orientation and thus influences the structure of materials. In metalworking, metal stock is passed through one or several pairs of rollers to decrease the thickness and increase the strength.…”

Section: Resultsmentioning

confidence: 99%

Stretching-induced ion complexation in physical polyampholyte hydrogels

et al. 2016

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Recently, we have developed a series of charge balanced polyampholytes (PA) physical hydrogels by random copolymerization in water, which show extraordinarily high toughness, self-healing ability and viscoelasticity. The excellent performance of PA hydrogels is ascribed to the dynamic ionic bonds formation through inter-and intra-chain interactions. The randomness makes ionic bonds of a wide strength distribution, the strong bonds, serve as permanent crosslinking, imparting the elasticity, while the weak bonds reversibly break and re-form, dissipating energy. In this work, we developed a simple physical method, named as pre-stretch method, to promote the performance of PA hydrogels.By imposing a pre-stretch on the sample at as-prepared state, the ion complexation during dialysis is prominently accelerated and the final performance is largely promoted. Further analysis suggests that the strong bonds formation induced by pre-stretch is responsible for the change in final performance. Pre-stretch decreases the entropy of system and increases the chain alignment, resulting in an increased possibility for strong bonds formation.

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Nonequilibrium Nature of Flow-Induced Nucleation in Isotactic Polypropylene

Cited by 66 publications

References 40 publications

Exploring the polymorphic behavior of a β‐nucleated propylene‐ethylene random copolymer under shear flow

Exploring the polymorphic behavior of a β‐nucleated propylene‐ethylene random copolymer under shear flow

Probing into the epitaxial crystallization of β form isotactic polypropylene: From experimental observations to molecular mechanics computation

Stretching-induced ion complexation in physical polyampholyte hydrogels

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