力场对PAN干湿法／湿法初生纤维结晶及其取向结构的影响

The Effect of the Force Field on the Crystalline and Orientation Structure of PAN Nascent Fiber during Dry Jet Wet-Spinning and Wet-Spinning Processes

利用广角X射线衍射(WAXD)研究了聚丙烯腈(PAN)干湿法及湿法初生纤维晶区及其取向结构的形成过程。结果表明,干湿法和湿法初生纤维的结晶度和Hermann取向因子随剪切速率和牵伸力增加而增大,相同条件下湿法制备的初生纤维晶区取向较优。干湿法过程中,由于牵伸张力在空气层段的集中,分子链凝固相分离过程发生在相对较弱的力场环境下,降低了结晶过程晶区的取向。湿法过程中,受到剪切作用的分子链直接进入凝固浴后即进入结晶过程,晶区取向度在张力诱导下相对较高。根据上述研究结果,提出了凝固过程中结晶及取向结构形成的分子链演变模型。

Wide angle X-ray diffraction （WAXD） was applied to study the Hermann orientation factor and crystallinity of PAN nascent fiber obtained by dry jet wet-spinning and wet-spinning methods, respectively. Based on the azimuthal scan results, it was indicated that with the increasing of shear rate and drawing ratio, the Hermann orientation factor of the nascent fiber gradually improved. At the same shear rate and drawing ratio, compared with the nascent fiber made by dry jet wet-spinning, the orientation factor of the nascent fiber produced by wet spinning is higher. During the dry jet wet- spinning process, the crystallization was occurred under weak stretching since the drawing force was focus on the soft part in air layer. Therefore, the Hermann orientation factor was reduced. However, in the wet-spinning process, the crystallization occurred immediately after extrusion, the drawing force induced the increasing of the orientation for crystalline region. The model for the evolution of the aggregation state of PAN molecular chains Was proposed.