超临界流体辅助醋酸纤维素溶液加工的流变性能

Rheological Properties of Cellulose Acetate Solution in Extrusion Processing Assisted by Supercritical Fluid

为了改善二醋酸纤维素(CDA)加工的流变性能,采用超临界二氧化碳辅助CDA溶液单螺杆挤出加工,通过狭缝流变仪进行流变测试,研究了注入超临界二氧化碳和加工条件(挤出温度、溶剂含量)对CDA溶液流变行为的影响。结果表明,CDA溶液和CDA/CO_2溶液体系均是非牛顿假塑性流体;CDA溶液和CDA/CO_2溶液体系的剪切黏度随着挤出温度或溶剂量的增加而降低;注入超临界二氧化碳显著降低了CDA溶液的黏度、挤出温度、剪切黏度对温度的敏感程度、口模压力和溶剂量,提高CDA溶液的挤出流量和非牛顿指数。随着温度升高,6 r/min和8 r/min时CDA/CO_2溶液体系黏度下降值大,黏度降低值可以达到47.93%;同一溶剂含量下,6 r/min时注入超临界二氧化碳后CDA溶液黏度下降值较大,降低值可以达到48.10%。

In order to improve the rheological properties of cellulose diacetate （CDA）, supercritical carbon dioxidewas injected into the CDA solution by single screw extrusion processing and the rheological behaviors were characterized by a slit rheometer. The effects of supercritical carbon dioxide and different processing factors （extrusion temperature and content of solvent） on rheological properties of CDA solution were investigated. The results show that the CDA solution and the CDA/CO2 solution system are non-Newtonian pseudoplastic fluid. With increasing of the extrusion temperature or the content of solvent, the shear viscosity of CDA solution with and without CO2 decreases. The presence of supercritical CO2 remarkably reduces the viscosity, the extrusion temperature, effect of temperature on the shear viscosity, the die pressure and the concentration of solvent of CDA solution, improving the extrusion flow and non-Newtonian index of CDA solution. With increasing of the extrusion temperature, the viscosity of CDA/CO2 solution system decreases greatly when the screw speeds are 6 r/min and 8r/ min, the reduction of viscosity can he up to 47.93%. Under the same condition of content of solvent, the supercritical CO2 has a great influence on the viscosity reduction of CDA solution at 6 r/min and the reduction of viscosity can be up to 48.10 %.