凝固条件对PAN初生纤维微结构的影响

Effect of coagulation conditions on microstructure of as-spun PAN fiber

通过湿法纺丝工艺制备聚丙烯腈(PAN)初生纤维,借助于X射线衍射仪、声速仪、扫描电子显微镜、小角X光散射仪等,研究了凝固浴温度、凝固浴浓度、喷丝头拉伸等凝固条件对初生纤维晶态结构、取向结构、形态结构的影响。结果表明:PAN纤维的凝聚态结构和形态结构在初生纤维形成时已基本形成;PAN初生纤维的结晶度达40%以上,其结晶度和结晶尺寸受凝固浴温度和浓度的影响;PAN初生纤维和原丝的晶区取向和全取向随着喷丝头拉伸的增大而增大;PAN初生纤维具有沿纤维轴向高度取向的沟槽,通过改变成形条件,可以获得沟槽浅且规整性完美的纤维表面;提高凝固浴浓度,可以形成结构均质、致密的PAN初生纤维,避免皮芯结构及芯部出现较多孔洞。

An as-spun polyacrylonitrile （PAN） fiber was prepared via wet spinning process. The effects of coagulation bath temperature and concentration and spinneret draft on the crystalline structure, orientation structure and morphology of the as-spun fiber were investigated with X-ray diffractometer, sound velocimeter, scanning electron microscope, small-angle X-ray scatterometer, etc. The results showed that the agglomerate structure and morphology of PAN fiber were almost formed when the as-spun fiber was farbricated; the crystallinity of as-spun PAN fiber was above 40%, and the crystallinity and the crystal size were affected by the coagulation bath temperature and concentration. The crystalline orientation and full orientation of the as-spun PAN fiber and PAN precursor were increased with the increase of spinneret draft. The as-spun PAN fiber had the highly orientated grooves along with the fiber axis. The fiber surface with shallow grooves and perfect regularity can be obtained by adjusting formation conditions. The increase of coagulation bath concentration contributed the uniform and compacted structure to the as-spun PAN fiber and avoided the formation of sheath-core structure and considerable holes in core part.