Synchrotron wide‐angle x‐ray diffraction of single‐filament PPTA fibers under stress
Synchrotron wide‐angle x‐ray diffraction of single‐filament PPTA fibers under stress
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DOI：
10.1002/polb.1991.090291016
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发表时间：
1991-09
期刊：
影响因子：
--
通讯作者：
Yingjie Li;Chi Wu;B. Chu
中科院分区：
文献类型：
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作者：
Yingjie Li;Chi Wu;B. Chu
由于完全延伸的大分子链，聚对苯二甲酸乙二酯(PPTA)纤维表现出高拉伸强度、高杨氏模量、高热稳定性和低蠕变。与通常的结晶聚合物不同，这种聚合物的链条高度延伸，横向有序性差，即使在非晶区也是如此。广角x射线衍射(WAXD)和小角x射线散射(SAXS)已经被用来研究晶格结构以及晶格结构、形态和宏观性质之间的关系，无论有没有应力？-5然而，这些研究只使用了纤维束。由于PPTA纤维在断裂前获得的变形非常有限，因此只能观察到X射线衍射图中非常小的角度变化。因此，每个细丝中的应力分布和细丝的轻微错位很容易影响WAXD的结果。在之前的一次通信中，我们成功地证明了利用布鲁克海文国家实验室(BNL)国家同步辐射光源(NSLS)的高通量同步辐射X射线源，可以测量到凯夫拉49(杜邦商标)纤维单丝的赤道衍射图。在这里，我们用三种PPTA纤维中的单丝，c为纤维轴和拉伸方向，用WAXD研究了晶格在a和b方向上的形变。
Fibers of poly (p-phenylene terephthalamide)(PPTA) show high tensile strength, high Young's modulus, high thermal stability, and low creep,'due to the fully extended macromolecular chains. Unlike the usual crystalline polymers, the chains are highly extended with poor lateral order, in the so-called paracrystalline structure even in the noncrystalline zone.'Wide-angle x-ray diffraction (WAXD) and small-angle x-ray scattering (SAXS) have been used to study the lattice structure and the relation between the lattice structure, the morphology, and the macroscopic properties, with or without stress?-5 However, these studies employed fiber bundles exclusively. Only a very small angular change in the x-ray diffraction pattern could be observed because PPTA fibers attain very limited deformation before they are broken. Therefore, the stress distribution in each filament and the slight misalignment of the filaments could easily smear the results of WAXD. In a previous Communication,'we demonstrated successfully that the equatorial diffraction patterns of a single filament of Kevlar 49 (a DuPont trademark) fiber could be measured by taking advantage of the high-flux synchrotron x-ray source at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory (BNL). Here we present our results of the WAXD studies of the lattice deformation in a and b directions using a single filament each of the three PPTA fibers, with c being the fiber axis and the stretching direction.