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.
Highlights
Carbon fibers (CFs) are defined as one kind of high performance fiber containing at least 92 wt% carbon [1] which have achieved global interest owing to the advantages of high tensile properties, low densities, high thermal and chemical stabilities
The mechanical properties of the PAN fibers treated in Sc-CO2 at different pressures were tested in this article and the changes in the mechanical properties of PAN fibers were obtained, as shown in PAN fibers was very sensitive to pressure which might be attributed to changes in CO2 concentration
Under the action of tension and heat, the molecular chains of PAN fibers moved in the direction of tension, which increased the degree of orientation of the fibers
Summary
Carbon fibers (CFs) are defined as one kind of high performance fiber containing at least 92 wt. % carbon [1] which have achieved global interest owing to the advantages of high tensile properties, low densities, high thermal and chemical stabilities Because of these superior properties, CFs are well known as carbonaceous reinforcing materials utilized increasingly in fields ranging from the aerospace industry to sport products [2,3,4]. PAN is key in determining the performance of CFs, that is to say, only high-performance PAN precursors precursors can produce high‐performance. We can study new ways to improve can produce high-performance CFs. we can study new ways to improve the performancethe of performance of PANimproving fibers, thereby improving the performance of CFs. PAN fibers, thereby the performance of CFs. K and which c = 304.1 c = 73.7 be in moderate process conditions.
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