X‐ray scattering studies of orientation in channel flows of a thermotropic liquid–crystalline polymer
X‐ray scattering studies of orientation in channel flows of a thermotropic liquid–crystalline polymer
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热致液晶聚合物通道流方向的 X 射线散射研究
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
W. Burghardt
中科院分区：
文献类型：
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作者：
D. Cinader;W. Burghardt
本文报道了在槽道流动中对一种商用热致熔体进行的原位广角X射线散射（WAXS）取向测量。这项调查包括广泛的检查混合剪切拉伸运动学产生的渠道流动与不同的横截面的方向效应。在狭缝收缩流中的拉伸梯度产生取向的大的增加，类似于在溶致物中所看到的那些。在尖锐的狭缝膨胀流中，观察到一个双峰取向状态，其中一个人口在下游方向对齐，而另一个位于垂直于预期的局部流线。这归因于在膨胀区域中横向于流动方向的拉伸。在一个逐渐扩张的过程中，较弱的伸展梯度导致较小的影响。沿障碍物上游和下游中心线的流动沿着导致与膨胀和收缩中观察到的行为类似的行为，而围绕90°急剧弯曲的流动产生跟踪预期流线的取向，而取向程度没有显著变化。© 1999 John Wiley & Sons，Inc.聚合物科学杂志B：聚合物物理37：3411-3428，1999
In situ wide-angle X-ray scattering (WAXS) orientation measurements are reported for a commercial thermotropic copolyester melt in channel flows. This investigation includes extensive examination of the orientation effects of mixed shear-extensional kinematics produced by channel flows with varying cross sections. Extensional gradients in a slit-contraction flow produce large increases in orientation, similar to those seen in lyotropes. In sharp slit-expansion flow, a bimodal orientation state is observed in which one population is aligned in the downstream direction while the other lies perpendicular to the expected local streamlines. This is attributed to stretching transverse to the flow direction in expansion regions. Weaker extensional gradients in a gradual expansion lead to a smaller effect. Flow along the centerline upstream and downstream of an obstruction leads to behavior similar to that observed in expansions and contractions, while flow around a sharp 90° bend produces orientation that tracks the expected streamlines, without significant change in the degree of orientation. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3411–3428, 1999