涤纶工业丝等温收缩中的结构变化

THE STRUCTURE CHANGES OF INDUSTRIAL YARN OF POLY(ETHYLENE TEREPHTHALATE)DURING ISOTHERMAL SHRINKAGE PROCESS

采用广角X 射线衍射、密度梯度、声速和差示扫描量热等实验方法对 145 5dtex/ 110f成品涤纶工业丝等温收缩的结构变化进行了表征 ,外加张力为 0 3N ,测定温度范围 375～ 494K .结果表明 ,涤纶工业丝的热收缩在宏观上表现为速率不同的两个过程 ,对应两种不同机理 .其中快过程对应非晶区的解取向 ,对收缩的贡献是主要的 ;慢过程对应晶区的变化 ,包含了晶粒的增长 ,新的不完善晶粒的形成和晶区的完善 .晶粒的增长在较短的时间内基本完成 ,再结晶则存在于整个收缩过程 .随温度的升高 ,晶区变化速度明显加快 ,对非晶区解取向的抑制效应因此变大 .

The structure changes of the industrial yarn of poly(ethylene terephthalate)(PET)of 1455dTex/110f under the tension of 0\^3N and at the temperature range of 375～494K were characterized by WAXD, density gradient method, sonic velocity measurements,and DSC.The shrinkage could be divided into two different processes characterized by different relaxation times and final shrinkage amounts.The molecular mechanism for the first process, the fast and dominant one, mainly was the disorientation of the extended segments in the amorphous region, which can be proved by the change of orientation function of the amorphous region( f am )with shrinkage time at different temperatures. More meaningful thing is that the shape and change tendencies of f am and relative length ( l \-t) with shrinkage time are very similar. The second slow one was resulted from the restructuring of the crystalline region, which included the rapid growth of the crystallites, the formation of new imperfect crystals and the reorganization of existed crystals during the whole shriknage process. The changes of crystalline regions became fast with the temperature rising and consequently their effect of restriction of the disorientation of the amorphous region became more obvious. However, the orientation function of crystalline regions keeps unchanged almost during the thermal shrinkage process. It should be indicated that the structure changes of amorphous and crystalline regions are not independently. Each process proceeds and competes each other during the thermal shriknage.The contribution of both processes to the shrinkage mainly depends on the temperature and time.The study of structure change of PET yarn during thermal shrinkage provides an important idea of developing more perfect crystalline regions to limit the thermal shrinkage due to the disorientation in amorphous regions.PET yarns with strength of 7cN/dTex,modulus of 4\^4cN/dTex at 5% elongation and thermal shrinkage of 3\^5% have been successfully obtained.