热处理增强热致液晶聚酯纤维及机理的研究

Investigation of Enhancing the Mechanical Strength of the Thermotropic Liquid Crystalline Polyester Fibers by Heat Treatments and the Mechanism

本文深入探讨了热处理对热致液晶聚酯(TLCP)纤维强度提升的作用机理。随热处理温度提升,TLCP纤维强度与模量明显提高。基于二维广角X射线衍射(WAXD)、差示扫描量热法(DSC)与流变仪等表征手段对纤维分子多级结构的分析,结果表明,热处理增强TLCP纤维强度的作用机理依赖热处理温度。热处理对TLCP纤维的取向结构无影响。当热处理温度低于250℃,TLCP纤维结晶度的提升引起纤维强度与模量的明显提高。提高处理温度至250℃以上,纤维结晶度呈下降趋势,纤维强度与模量的进一步提升归因为纤维分子量的增长,该行为是由于热处理过程纤维分子链固相缩聚与交联反应引起。

In this study,the mechanism for improving the mechanical properties of the thermotropic liquid crystalline polyester(TLCP)fibers was deeply studied.It is found that the strength and modulus are enhanced significantly with increasing the heat treatment temperatures.The multilevel structure of fiber molecule are analyzed by the 2D wide angel X-ray diffraction(WAXD),differential scanning calorimetry(DSC)and the rheometer.It is found that the mechanism for strength improvements of TLCP fibers relies on the heat treatment temperature which are selected.While the orientation structures of TLCP fibers are maintained almost unchanged,the crystalline degree are increased significantly,thus increasing the fiber strength,as the heat treatment temperature is under 250℃.However,as the treatment temperature is increased further above 250℃,the crystalline degree begins to decrease.As a result,the further significant improvement of the TLCP fiber strength is mainly attributed to the increase of the weight average molecular number of the TLCP fiber,which is induced by the solid polycondensation reactions and cross-linking reactions among the fiber molecule chains.