凝固条件对PAN初生纤维微结构的影响

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。

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

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 scatterom- eter,etc.The results showed that the agglomerate structure and morphology of PAN fiber were almost formed when the as-spun fi- ber 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 con- ditions.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.