Effects of melt structure on shear-induced β-cylindrites of isotactic polypropylene

Zhang, Bin; Chen, Jingbo; Ji, Fangfang; Zhang, Xiaoli; Zheng, Guoqiang; Shen, Changyu

doi:10.1016/j.polymer.2012.02.023

Cited by 82 publications

(63 citation statements)

References 76 publications

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“…It is reported that in the production of β ‐PP nucleated with β ‐nucleating agent, the key factors include the type, selectivity, efficiency of the used β ‐nucleating agents, the thermal and mechanical conditions, and the molecular structure of PP resins . Large amount of works have been performed on this issue, and great progresses have been made.…”

Section: Introductionmentioning

confidence: 99%

Investigation on the dynamic crystallization and melting behavior of β‐nucleated isotactic polypropylene with different stereo‐defect distribution—the role of dual‐selective β‐nucleation agent

Kang

Wang

Peng

et al. 2013

Polymers for Advanced Techs

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The selectivities of different β‐nucleating agents might be quite different from each other, which is important in determining the crystallization and properties of the obtained β‐isotactic polypropylene (β‐iPP). However, the relationship between molecular structure and dynamic crystallization behavior of β‐iPP nucleated by dual‐selective β‐nucleating agent (DS‐β‐NA) is still not clear. In this study, the dynamic crystallization and melting behavior of two β‐iPP with nearly same average isotacticity but different stereo‐defect distribution, nucleated by a DS‐β‐NA (N,N′‐dicyclohexyl‐2,6‐naphthalenedicarboxamide; trade name TMB‐5), were studied by differential scanning calorimetry, wide‐angle X‐ray diffraction, and scanning electronic microscopy. The results indicated that in the presence of TMB‐5, the dynamic crystallization and melting behavior of the samples are quite different because the joint effects of the dual selectivity of TMB‐5 and stereo‐defect distribution of the iPP under different cooling rates. Two important roles were observed: (i) slow cooling rate favors the formation of high β‐fraction; and (ii) high crystallization temperature favors the crystallization of α‐phase accelerated by TMB‐5. Generally, the dual selectivity of the DS‐β‐NA, the stereo‐defect distribution of iPP, and the cooling rate were important factors in determining the formation of β‐crystal. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Investigation on the dynamic crystallization and melting behavior of β‐nucleated isotactic polypropylene with different stereo‐defect distribution—the role of dual‐selective β‐nucleation agent

Kang

Wang

Peng

et al. 2013

Polymers for Advanced Techs

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“…Among these methods, the flow‐induced β ‐ i PP formation caught a lot of attention since 1973 . During the following decades, shear‐induced β ‐ i PP has been widely investigated in a variety of different situations: fiber pulling experiments , plate rheometry experiments , capillary rheometer , compression‐molding , and single‐screw extruder . Dragaun proved that to induce β ‐ i PP a critical average threshold value for the shear rate of approximately 300 s −1 had to be exceeded.…”

Section: Introductionmentioning

confidence: 99%

Competition effect of shear‐induced nuclei and multiwalled carbon nanotubes (MWCNT) on β‐isotactic polypropylene (iPP) formation in preshear injection‐molded iPP/MWCNT nanocomposites

et al. 2017

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In this study, the influence of multiwalled carbon nanotubes (MWCNT) on β‐isotactic polypropylene (iPP) formation in preshear injection‐molded iPP/MWCNT nanocomposites is investigated layer by layer by wide angle X‐ray diffraction (WAXD). WAXD results suggest that in preshear injection‐molded pure iPP, β‐iPP exists in not only the shear region, but also the core region as a result of preshear‐induced nucleation. The addition of MWCNT can inhibit the β‐iPP formation. As the depth away from the specimen surface is decreased, the inhibiting effect is decreased. The reason responsible for that is given as follows: (1) with the addition of MWCNT, extra nuclei are induced during preshear. Both MWCNT and extra nuclei serve as α‐iPP nucleation point. Therefore, the formation of β‐iPP is restricted; (2) the cooling rate gradient is widely accepted to exist in the injection molded sample. A larger cooling rate at a smaller depth will give rise to a lower α‐iPP crystallization onset temperature and a lower nucleation efficiency of MWCNT. Since that β‐iPP grows only in the temperature range of 105°C‐140°C, the inhibiting effect of MWCNT on β‐iPP becomes weaker as the depth is decreased. POLYM. COMPOS., 39:E1149–E1158, 2018. © 2017 Society of Plastics Engineers

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“…To achieve better toughness, the enhancement of b-form content is an efficient way. However, the b-form can be obtained in large amount only under several specific conditions such as shearing [15][16][17][18][19], using specific b-nucleating agents (b-NA) [20][21][22][23] and directional crystallization in temperature gradient [24].…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al [18,19] investigated effects of ordered structures and shear flow on polymorphic nature of b-cylindrites of iPP and found that the survived ordered structures may remain in the melt which can act as shear-precursor during recooling, initiate the shear-induced crystallization and encourage the formation of b-cylindrites. Liu et al [15,44,45] introduced partly melting iPP fiber to homogeneous supercooled iPP melt, and systematically investigated the b-crystallization of iPP/iPP single fiber composite.…”

Section: Introductionmentioning

confidence: 99%

Influence of melt structure on the crystallization behavior and polymorphic composition of polypropylene random copolymer

et al. 2015

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Effects of melt structure on shear-induced β-cylindrites of isotactic polypropylene

Cited by 82 publications

References 76 publications

Investigation on the dynamic crystallization and melting behavior of β‐nucleated isotactic polypropylene with different stereo‐defect distribution—the role of dual‐selective β‐nucleation agent

Investigation on the dynamic crystallization and melting behavior of β‐nucleated isotactic polypropylene with different stereo‐defect distribution—the role of dual‐selective β‐nucleation agent

Competition effect of shear‐induced nuclei and multiwalled carbon nanotubes (MWCNT) on β‐isotactic polypropylene (iPP) formation in preshear injection‐molded iPP/MWCNT nanocomposites

Influence of melt structure on the crystallization behavior and polymorphic composition of polypropylene random copolymer

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