Studies of structure and morphology development during the heat-draw process of nylon 66 fiber by synchrotron X-ray diffraction and scattering techniques
Studies of structure and morphology development during the heat-draw process of nylon 66 fiber by synchrotron X-ray diffraction and scattering techniques
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DOI：
10.1107/s0021889897001842
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发表时间：
1997-12-01
影响因子：
6.1
通讯作者：
Harney, P
中科院分区：
文献类型：
--
作者：
Hsiao, BS;Kennedy, AD;Harney, P
利用同步辐射广角X射线衍射（WAXD）和小角X射线散射（SAXS）技术对尼龙66纤维在不同温度下连续拉伸过程中的结构和形态变化进行了在线研究。从二维（2D）WAXD测量，确定晶胞参数。结果证实，在布里尔转变温度（约443 K）以上，三斜晶胞结构仍然存在。随着温度的升高，晶胞尺寸a（主要由氢键）几乎保持不变，而B增加和c减少（都显示了一个阶跃变化在403 K，布里尔转变之前）。a的恒定值与氢键在熔融之前的高温下相对不动的论点一致。B和c的阶跃变化表明，在Brill转变之前，小的（或有缺陷的）晶体的预熔化过程。因此，幸存的较大晶体的各向异性热膨胀导致阶跃变化行为。这一假设与晶体密度数据以及SAXS的形态评价一致。从2D SAXS数据中提取了几个维度：由相关函数方法确定的层状晶体和非晶厚度（沿着纤维）和由孔隙分析确定的晶纤宽度（垂直于纤维）。这些结果还表明，拉伸消除了小晶体，但应变效应远小于温度效应。
Online studies of structure and morphology development during continuous drawing of a nylon 66 fiber at different temperatures were carried out using synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. From the two-dimensional (2D) WAXD measurement, unit-cell parameters were determined. The results confirm that the triclinic cell structure persists above the Brill transition temperature (about 443 K). With increasing temperature, the unit-cell dimension a (dominated by hydrogen bonding) remains almost unchanged, while b increases and c decreases (both show a step-change at 403 K, prior to the Brill transition). The constant value of a agrees with the argument that the hydrogen bonding is relatively immobile at high temperatures prior to melting. The step-changes in b and c suggest that a premelting process of small (or defective) crystals precedes the Brill transition. As a result, the anisotropic thermal expansion of the surviving larger crystals results in a step-change behavior. This hypothesis is consistent with the crystal density data as well as the morphology evaluation by SAXS. Several dimensions were extracted from the 2D SAXS data: lamellar crystal and amorphous thicknesses (along the fiber) determined by the correlation function method and crystal fibril width (perpendicular to the fiber) determined by the Pored analysis, These results also indicate that drawing annihilates small crystals, but the strain effect is much less than the temperature effect.