Effect of Different Pressures of Supercritical Carbon Dioxide on the Microstructure of PAN Fibers during the Hot-Drawing Process

Mengmeng Qiao; Haijuan Kong; Xiaoma Ding; Zhifeng Hu; Luwei Zhang; Yuanzhi Cao; Muhuo Yu

doi:10.3390/polym11030403

Effect of Different Pressures of Supercritical Carbon Dioxide on the Microstructure of PAN Fibers during the Hot-Drawing Process

Polymers (Basel). 2019 Mar 1;11(3):403. doi: 10.3390/polym11030403.

Authors

Mengmeng Qiao¹, Haijuan Kong², Xiaoma Ding³, Zhifeng Hu⁴, Luwei Zhang⁵, Yuanzhi Cao⁶, Muhuo Yu⁷

Affiliations

¹ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China. 2160320@mail.dhu.edu.cn.
² School of Materials Engineer, Shanghai University of Engineer Science, Shanghai 201620, China. Konghaijuan@sues.edu.cn.
³ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China. 1159124@mail.dhu.edu.cn.
⁴ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China. 2160226@mail.edu.cn.
⁵ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China. 2170293@mail.dhu.edu.cn.
⁶ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China. 2180410@mail.dhu.edu.cn.
⁷ State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China. yumuhuo@dhu.edu.cn.

Abstract

The hot-drawing process of polyacrylonitrile (PAN) fibers is an important step during the production of PAN-based carbon fibers. In this study, supercritical carbon dioxide (Sc-CO₂) was used as one kind of media for thermal stretching of PAN fibers to study the effect of different pressures of Sc-CO₂ on crystallinity, degree of orientation and mechanical property of PAN fibers during the hot-drawing process. The changes of microstructure and mechanical properties in the PAN fibers were investigated by wide-angle X-ray diffraction, small angle X-ray scattering and monofilament strength analysis. The results showed that as the pressure increased, the crystallinity and degree of orientation of PAN fibers increased. Furthermore, when the pressure was 10 MPa, the crystallinity increased from 69.78% to 79.99%, which was the maximum crystallinity among the different pressures. However, when the pressure was further increased, the crystallinity and degree of orientation of the fibers were reduced. The test results of the mechanical properties were consistent with the trends of crystallinity and degree of orientation, showing that when the pressure was 10 MPa, the tensile strength of the fibers increased from 4.59 cN·dtex^-1 to 7.06 cN·dtex^-1 and the modulus increased from 101.54 cN·dtex^-1 to 129.55 cN·dtex^-1.

Keywords: crystallinity; degree of orientation; hot-drawing; mechanical property; polyacrylonitrile fibers; supercritical carbon dioxide.

Grants and funding

Grant No.51603120 , 11604204/the National Natural Science Foundation of China