乙基醋酸纤维素液晶态条带织构的形成机理

本文应用平行板移动式和转动式二种剪切装置研究了乙基醋酸纤维素的二氯乙酸体系液晶态受剪过程形成条带织构的临界剪切速率,条带织构的形成机理以及所形成的条带织构在升降温过程中的变化。结果表明,高分子液晶态受剪过程条带织构不是在受剪时产生,而是在受剪停止后的弛豫过程中形成的。可以观察到条带织构出现的诱导时间(t_b),其值的大小与溶液的浓度、剪切速率等因素有关。最后提出一模型来解释高分子液晶态受剪切过程条带织构的形成机理。

FORMATION MECHANISM OF A BAND TEXTURE IN CHO- LESTERIC SOLUTION OF ETHYL CELLULOSE ACETATE

The formation mechanism of a band texture of ethyl cellulose acetate (ECA) in dichloro-acetic acid (DCA) which exhibits a cholesteric mesophase has been investigated by using a parallel plates shearing apparatus. A critical shear rate of the band texture formation can be measured to be about 1.5 sec-1 for 30 wt% solution of ECA. The result obtained indicates that the band texture of ECA/DCA is not formed during shear, but it is formed during relaxation of shear orientation. The variation of the formed band texture was also studied during heating, and found that the formed band texture will vanish at heating, but the macromolecular chain orientation persists in solution. If the temperature is lower the isotropic temperature of the solution the band texture will reappear during cooling. Finally, a model was suggested to describe the formation mechanism of band texture for liquid crystalline state of polymers by shear.