PAN原丝成形过程中孔隙结构的形成和演变

采用干湿法纺丝在梯级凝固成形条件和后续工艺下得到聚丙烯腈(PAN)原丝,利用扫描电镜、氮气吸附等方法测试研究了PAN原丝中孔隙的形成和演变。结果表明:在凝固成形阶段,PAN原丝内孔隙的形成是溶剂和非溶剂双扩散及PAN相分离双重作用的结果;PAN原丝经过沸水拉伸、干燥致密化、饱和蒸汽拉伸和热定型等处理,其纤维密度、结晶度增大,力学性能提高,其孔隙平均孔径、孔隙体积和孔隙含量均逐渐减小;PAN原丝内闭合孔隙经过拉伸后会形成新的开放孔隙,开放孔隙在干燥致密化后闭合和消失。

Formation and evolution of porosity structure of PAN precursor during fiber formation process

Polyacrylonitrile(PAN) fiber was prepared by dry wet spinning under gradient coagulation formation and after processing conditions.The formation and evolution of the porosities in PAN precursor were studied by scanning electron microscopy and nitrogen adsorption.The results showed that the porosity formation of PAN precursor resulted from the combination of double diffusion of solvent and nonsolvent and the phase separation of PAN.The density and crystallinity of the fiber were increased,the mechanical properties were improved,the average pore diameter and porosity volume and content were gradually decreased as the PAN precursor was subjected to boiling water drawing,dry collapse,saturated vapor drawing and heat setting processes.The close porosity in PAN precursor transformed into new open porosity after drawing which closed and disappeared after dry collapse.