摘要:
应用小角X射线散射等方法,系统、定量地测试表征了聚丙烯腈基碳纤维原丝中纳米孔的尺寸、形状、体积分数、单位体积中纳米孔绝对数量以及纤维总孔洞率等形态结构参量,并对这些参量在水洗、水洗牵伸、热致密化、高压蒸汽牵伸及热稳定化等工艺过程中的变化规律及原因进行了研究.结果表明,纺丝过程中牵伸及高温热处理均可使纤维总孔洞率逐步下降.纳米孔尺寸体积分数Vi测试表明,对于小于10 nm3的小纳米孔和大于103 nm3的较大纳米孔,两者的Vi在纺丝初期水洗牵伸工艺中分别为0.217和0.369,而在纺丝后期热稳定化处理后发生大幅度改变,分别为0.948与0.015.其原因并不是在高压蒸汽牵伸及热稳定处理中较小纳米孔含量的增加,而是较大纳米孔含量的大幅度减少.纳米孔形状研究表明,纺丝工艺中的多次牵伸处理均使纳米孔的长短轴比加大,而大于玻璃化温度的热处理均使纳米孔长短轴比收缩,并且对于较小纳米孔来说这种收缩更为显著.
Abstract:
In this paper, we quantitatively characterize the morphological structure parameters including the nanopore size, shape, volume fraction, absolute number of nanopores and total prosity of polyacrylonitrile based carbon fiber precursor. Meanwhile, the change law and reason in the process of washing, drawing in washing, heat-densification, drawing in high pressure steam and hoting-stabilization are investigated. Results show that spinning drawing and high-temperature heat treatment make the prosity of fibers decline gradually in the process of fabrication. The result of micropore volume fraction Vi shows that at the beginning of the spinning and drawing in washing process the Vi of smaller nanopore which is less than 10 nm3 and the Vi of greater nanopore which is larger than 103 nm3 are 0.217 and 0.369, respectively, while these values sharply turn to 0.948 and 0.015 after the late spinning process of hoting-stabilization. The reason for this is not the increase of content of smaller nanopore content in the drawing process in high pressure steam and hoting-stabilization, but the sharp decrease of the greater nanopore content. The result about nanopore shape shows that the spinning multiple drawing in the process increases the axial (long-axis-to-short-axis) ratio of nanopores, while heat treatment over the glass transition temperature reduces the axial ratio of nanopore, and this shrinkage is more significant for smaller nanopores.
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