Pressure-driven startup flows of liquid crystalline polymers through slit cells

被引:0
|
作者
Noriyasu Mori
Masatada Shindo
Kiyoji Nakamura
Takehiro Yamamoto
机构
[1] Osaka University,Department of Mechanophysics Engineering, Graduate School of Engineering
来源
Rheologica Acta | 2003年 / 42卷
关键词
Wavy texture; Liquid crystalline polymers; Slit flows; Light scattering;
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学科分类号
摘要
A wavy texture occurs in the flows of liquid crystalline polymers through a slit cell. In the present paper the development of the wavy texture is examined in pressure-driven startup flows for four types of slit cells, using a liquid crystalline solution of 50 wt% hydroxypropylcellulose (HPC). There exists a comparatively long induction period until the wavy texture appears after the startup of the flow, and the induction time decreases with increasing apparent shear rate. However, it is found that the apparent shear strain at which the wavy texture emerges is independent of the apparent shear rate though the value of the apparent shear strain slightly varies with the type of flow cell. Furthermore, the light scattering experiments are carried out to examine the structure of wavy texture. After the startup of the flow, a homogeneous pattern of the light scattering quickly shrink in size and a spike pattern perpendicular to the flow direction is emphasized. While the wavy texture is seen, the ellipsoidal pattern of light scattering oscillates with the same frequency as the passage of the wavy texture. A structure of scattering objects in the wavy texture is proposed, based on the observation of change in the light scattering pattern with time.
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页码:527 / 533
页数:6
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