Understanding the Morphological and Structural Evolution of α- and γ-Poly(vinylidene fluoride) During High Temperature Uniaxial Stretching by In Situ Synchrotron X-ray Scattering,Industrial & Engineering Chemistry Research

当前位置： X-MOL 学术 › Ind. Eng. Chem. Res. › 论文详情

Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)

Understanding the Morphological and Structural Evolution of α- and γ-Poly(vinylidene fluoride) During High Temperature Uniaxial Stretching by In Situ Synchrotron X-ray Scattering
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2020-09-21 , DOI: 10.1021/acs.iecr.0c03510
Yue Li ₁ , Guo-Qi Ma ₁ , Yan Sun ₂ , Hua-Dong Huang ₁ , Ming-Wang Pan ₃ , Guoqiang Zhang ₄ , Gan-Ji Zhong ₁ , Zhong-Ming Li ₁

Affiliation

Poly(vinylidene fluoride) (PVDF) is rich in different polymorphs. Among them, β-phase PVDF is of technical importance because of its strong spontaneous polarization and desired piezoelectric properties. Phase transformation via physical deformation is demonstrated to be a facile approach to obtain a high content of electroactive β-phase from other less or nonpolar phases. Over the past few decades, deformation induced α–β transformation has been intensively researched. In contrast, there is a significant lack of study on obtaining β-phase from other important PVDF phases, i.e., γ-phase, probably due to difficulty in obtaining the pure γ-phase. In this work, the pure γ-phase was induced by an ion–dipole interaction and was subjected to uniaxial stretching along with the pure α-phase at 150 °C. By means of in situ synchrotron X-ray scattering, the evolution of the lamella morphology and crystal structure over tensile deformation was carefully investigated. Corresponding to macroscopic yielding, necking, and strain hardening shown on the stress–strain curves, the crystal superstructure underwent a microscopic transition from lamellar to fibrillar morphology, proceeding in the order of interlamellar shearing, crystallographic crystal slip, lamellae fragmentation, and block alignment. Phase transformation was observed to mainly occur when the chains in the amorphous region were extensively stretched, and crystals were sheared to rotate and slip. The γ-phase exhibited a two-step transformation with a significantly higher transformation efficiency to the β-phase at the end of the deformation. Instead, α-crystals were predominately oriented under stretching with only a small portion being converted to the β-phase. When the small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) results are combined, it is proposed that the strong yet heterogeneous stress and creation of void defects as well as the lower energy barrier for the conformational change collectively contribute to the favoring of phase transformation in the γ-phase sample. This work advances our understanding about polymorphic transformation in PVDF as well as leads the way for researching an optimal route to obtain a high content of the β-phase.

中文翻译：

通过原位同步加速器X射线散射了解高温单轴拉伸过程中α-和γ-聚偏二氟乙烯的形貌和结构演变

聚偏二氟乙烯（PVDF）富含不同的多晶型物。其中，β相PVDF由于其强的自发极化和所需的压电性质而具有技术重要性。已证明，通过物理变形进行相变是一种从其他较小或非极性相中获得高含量电活性β相的简便方法。在过去的几十年中，对变形引起的α-β转变进行了深入研究。相反，从其他重要的PVDF相（即γ相）获得β相的研究非常缺乏，这可能是由于难以获得纯γ相造成的。在这项工作中，纯γ相是通过离子-偶极相互作用诱导的，并在150°C下与纯α相一起经受单轴拉伸。通过原位同步加速器X射线散射，仔细研究了薄片形貌和晶体结构在拉伸变形过程中的演变。对应于应力-应变曲线上显示的宏观屈服，颈缩和应变硬化，晶体的上部结构经历了从层状到纤维状形态的微观转变，顺序为层间剪切，晶体学晶体滑移，层状碎片和块排列。观察到相变主要发生在无定形区域中的链被广泛拉伸，并且晶体被剪切以旋转和滑动时。在变形结束时，γ相表现出两步相变，与β相相比具有明显更高的相变效率。代替，α晶体主要在拉伸下取向，只有一小部分转变为β相。当将小角度X射线散射（SAXS）和广角X射线衍射（WAXD）结果相结合时，提出了强而异质的应力和空隙缺陷的产生以及较低的能垒。构象变化共同有助于γ相样品中的相变。这项工作提高了我们对PVDF中多态转化的理解，并为研究获得高含量β相的最佳途径提供了途径。有人提出，强而又不均匀的应力和空隙缺陷的产生以及构象变化的较低能垒共同有助于γ相样品中的相变。这项工作提高了我们对PVDF中多态转化的理解，并为研究获得高含量β相的最佳途径提供了途径。有人提出，强而又不均匀的应力和空隙缺陷的产生以及构象变化的较低能垒共同有助于γ相样品中的相变。这项工作提高了我们对PVDF中多态转化的理解，并为研究获得高含量β相的最佳途径提供了途径。

更新日期：2020-10-15

点击分享查看原文

点击收藏

阅读更多本刊最新论文本刊介绍/投稿指南11