静电纺聚丙烯腈纳米纤维晶态结构及取向的形成

采用新型流动水浴收集方式制备出连续单向排列的静电纺聚丙烯腈(PAN)纳米初生纤维,收集静电纺丝不同阶段的静电纺PAN纳米纤维,并在热水中进行后牵伸,使其伸长至原长的2倍、3倍.通过扫描电子显微镜(SEM)、广角X射线衍射(WAXD)等方法对静电纺丝过程不同阶段的PAN纳米纤维的形貌、直径、致密性、晶态结构及取向进行了表征.研究表明,(1)在静电纺丝过程中PAN纺丝液射流受到牵伸作用,静电纺PAN纳米纤维的晶态结构形成并逐渐完善.纳米纤维的直径随着静电纺丝过程逐渐减小(从664 nm减小至353 nm),结晶度从42.55％增加至47.76％,晶区取向由37.48％提高至43.93％.纳米纤维致密性也逐渐提高(密度由1.1917 g/cm3增加至1.1943 g/cm3).(2)静电纺丝过程进入PAN射流溶剂含量较低的阶段后,继续通过静电纺丝过程提高纳米初生纤维晶态结构及取向的效果很有限,而通过热水后牵伸过程可进一步使晶态结构及取向得到有效果的完善.研究同时发现,静电纺初生纤维的晶态结构及取向与其在热水牵伸过程中的进一步完善具有相关性.

FORMATION OF THE CRYSTALLINE STRUCTURE AND ORIENTATION OF POLYACRYLONITRILE ELECTROSPUN NANOFIBERS

Continuous bundles of aligned electrospun polyacrylonitrile(PAN) precursor nanofibers of different stages in electrospinning process were prepared with a flowing water bath collector.Then the as-electrospun nanofiber bundles were stretched in hot water at 97℃ into 2 and 3 times of the original lengths.Subsequently,characterizations and evaluations were carried out to understand their morphology,diameter,density,crystalline structure and orientation using SEM,WAXD etc.The study revealed that:(1) the polymer solution jet was stretched/elongated during electrospinning process,which formed and improved the crystalline structure and orientation;during the electrospinning process,the diameter of as-electrospun nanofiber bundles was decreased from 664 nm to 353 nm,while the crystallinity and the orientation increased from 42.55% to 47.76% and 37.48% to 43.93%,respectively,which led to the density increased from 1.1917 g/cm3 to 1.1943 g/cm3;and(2) the improvement of the crystalline structure and orientation was limited when most solvent was removed during the electrospinning process,and post-spinning stretching could substantially improve the crystalline structure and orientation.Meanwhile,the improvement of the crystalline structure and orientation of as-electrospun nanofiber bundles could enhance the post-spinning stretching process.