Effects of strain rate and temperature on polymorphism in flow-induced crystallization of Poly(vinylidene fluoride)

Chu, Zhaozhe; Liu, Long; Liao, Yilong; Li, Wei; Zhao, Ruijun; Ma, Zhe; Li, Yuesheng

doi:10.1016/j.polymer.2020.122773

Cited by 13 publications

(15 citation statements)

References 63 publications

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“…However, it should be noted that the characteristic signals at 2θ = 14.9° of (020) α and (020) γ planes were absent, so those crystallites obtained were the β-phase. This suggests that the flow induces the formation of the PVDF β-phase in the presence of ions, as in neat PVDF . Although TBAHS ions facilitate the generation of the γ-phase under quiescent conditions, it is still the flow that determines polymorphism of crystallization, which happens during the flow.…”

Section: Resultssupporting

confidence: 90%

“…This suggests that the flow induces the formation of the PVDF β-phase in the presence of ions, as in neat PVDF. 55 Although TBAHS ions facilitate the generation of the γ-phase under quiescent conditions, it is still the flow that determines polymorphism of crystallization, which happens during the flow. Furthermore, the crystallinity indexes of the β-phase estimated from the 1D WAXD results are 2.0, 2.4, and 3.6% in neat PVDF, PVDF− CTAB, and PVDF−TBAHS, respectively.…”

Section: 2supporting

confidence: 90%

“…In this case, TTTG conformations formed by CTAB ions and flow have multiple origins. First, the flow-generated β-phase that is packed by the segments adapting the all-trans conformations can provide the TTT template for the adjustment of the TTTG conformation. , Second, flow directly induces the formation of the TTTG conformation, as the all-trans TTTT conformation, which has been demonstrated by the previous work that flow induces the appearance of the γ-phase in neat PVDF at 155 °C . Third, the TTTG conformation comes from the partial relaxation of the TTTT conformation …”

Section: Discussionmentioning

confidence: 86%

“…25,27 Second, flow directly induces the formation of the TTTG conformation, as the all-trans TTTT conformation, which has been demonstrated by the previous work that flow induces the appearance of the γ-phase in neat PVDF at 155 °C. 55 Third, the TTTG conformation comes from the partial relaxation of the TTTT conformation. 73 In principle, all three pathways are possible to happen in the flow-induced crystallization of neat PVDF, while the γ-phase is practically observed only in the presence of ions.…”

Section: Discussionmentioning

confidence: 99%

“…Meanwhile, flow is an inevitable factor in polymer melting processing, which can accelerate the crystallization kinetics and alter the modification of the obtained crystallites. − For PVDF, the application of flow can induce the direct formation of highly oriented β-phase from the melt, , and the oriented γ-phase can also be generated within the subsequent isothermal period after flow at a high temperature of 155 °C, which may be associated with the flow-induced gauche–trans transition. The all-trans sequence obtained by the flow-induced conformation transition provides the structural basis for the formation of the β-phase.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Ions on the Flow-Induced Crystallization of Poly(vinylidene fluoride)

et al. 2021

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The flow-induced crystallization of poly(vinylidene fluoride) (PVDF)−ion composites in the presence of externally added ions was investigated by in situ wide-angle X-ray diffraction (WAXD) and ex situ Fourier transform infrared (FTIR) spectroscopy. In this work, two types of hexadecyl trimethyl ammonium bromide (CTAB) and tetrabutylammonium hydrogen sulfate (TBAHS) ions with distinct electrostatic interactions were chosen at a weight concentration of 0.5% to design different influences on crystallization. For quiescent crystallization, TBAHS ions induced the appearance of the polar γ-phase with accelerated kinetics, but CTAB ions exhibited no detectable influence in the crystallization of the nonpolar α-phase as in neat PVDF. Interestingly, flow induced the formation of β-phase with prominent piezo/ferroelectricity and the presence of ions could increase the amount of this flow-generated β-phase. With a strain of 2.7 applied at 1 s −1 , the CTAB and TBAHS ions increased the crystallinity index of the β-phase obtained just after the flow to 2.4 and 3.6%, respectively, with respect to that of 2.0% in neat PVDF. In addition, the ions could increase the enhancement amplitude of the flow-generated β-phase by increasing the strain rate over a broad range from 0.01 to 10 s −1 . Moreover, both CTAB and TBAHS ions induced the crystallization of the γ-phase during the isothermal process at a high temperature of 160 °C, where the α-phase appearing in neat PVDF was completely suppressed.

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Section: Resultssupporting

confidence: 90%

Section: 2supporting

confidence: 90%

Section: Discussionmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Ions on the Flow-Induced Crystallization of Poly(vinylidene fluoride)

et al. 2021

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Recent Progress on Structure Manipulation of Poly(vinylidene fluoride)‐Based Ferroelectric Polymers for Enhanced Piezoelectricity and Applications

Zhang

Zhu

et al. 2023

Adv Funct Materials

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Poly(vinylidene fluoride) (PVDF)‐based polymers demonstrate great potential for applications in flexible and wearable electronics but show low piezoelectric coefficients (e.g., −d33 < 30 pC N−1). The effective improvement for the piezoelectricity of PVDF is achieved by manipulating its semicrystalline structures. However, there is still a debate about which component is the primary contributor to piezoelectricity. Therefore, current methods to improve the piezoelectricity of PVDF can be classified into modulations of the amorphous phase, the crystalline region, and the crystalline–amorphous interface. Here, the basic principles and measurements of piezoelectric coefficients for soft polymers are first discussed. Then, three different categories of structural modulations are reviewed. In each category, the physical understanding and strategies to improve the piezoelectric performance of PVDF are discussed. In particular, the crucial role of the oriented amorphous fraction at the crystalline–amorphous interface in determining the piezoelectricity of PVDF is emphasized. At last, the future development of high performance piezoelectric polymers is outlooked.

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Recent progress in flow‐induced polymer crystallization

Nie

Fan

Cao

et al. 2022

Journal of Polymer Science

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During industrial processing, such as film blowing and injection molding, semicrystalline polymers have to be subjected to external flow. Flow changes the nucleation rate, crystal morphology and polymorphism of polymers. As flow can be tunable, polymeric products with different macroscopic performance and versatile applications can be obtained. Understanding polymer crystallization with the presence of flow, or namely flow-induced crystallization (FIC), is crucial to optimize polymer processing parameters and to understand phase transition under far-from equilibrium conditions, as FIC is essentially a typical nonequilibrium process. Current review aims to summarizes recent achievements of FIC during last five years from three aspects: theory, experiment and simulation. First, we present the FIC model and theory, including the classical conformational entropy reduction model, the newly developed POLYdisperse STRain Accelerated Nucleation Dynamics (PolySTRAND) Model and uFIC Model. Then we discuss the FIC experiments under both well-controlled flow and complex processing conditions. Finally, we show the recent advance of FIC in computer simulation. With the fast development in modeling efficiency, more detailed nucleation and structure transition processes during FIC can be obtained, which promote the study of molecular mechanisms of FIC.

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Effects of strain rate and temperature on polymorphism in flow-induced crystallization of Poly(vinylidene fluoride)

Cited by 13 publications

References 63 publications

Effect of Ions on the Flow-Induced Crystallization of Poly(vinylidene fluoride)

Effect of Ions on the Flow-Induced Crystallization of Poly(vinylidene fluoride)

Recent Progress on Structure Manipulation of Poly(vinylidene fluoride)‐Based Ferroelectric Polymers for Enhanced Piezoelectricity and Applications

Recent progress in flow‐induced polymer crystallization

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