Study On The Microstructural Variation Of The PAN-based Carbon Fibre Precursor During The Production Process

Carbon fiber is a new carbon material that rise in the 1960s, and it is widely used in the defense (aerospace industry, military aircraft, etc), commercial, civil (aviation, sports, industrial and transportation, etc). It is an ideal functional and structural material, and it not only has high-temperature resistance, creep resistance, corrosion resistance, but also a small thermal expansion coefficient, good dimensional stability, high specific strength and specific modulus. Raw silk is the precursor of carbon fibre, the key factor to the manufacture of high quality carbon fibre is to improve the structural performance of the raw silk.It has been massive reported that X-ray detection technology had been widely used as an important analysis method on the PAN-based raw silk. In terms of research, studies nowadays focus on finished raw silk micro-structural features mainly, while the comprehensive study on structure formation process is rather rare.This article conducted a tracking test on the raw silks which were on the key process nodes with X-ray, in order to predominate the variation of the raw silk and it’s flaw, to improve the production process and to raise the production of raw silk. Using a wide angle X-ray diffraction (WAXD) technique to characterize, degree of crystallinity, variation of the degree of orientation, we can see that with the spinning processes going on, crystallinity and orientation of the fibre have gradually increased from WAXD figure. With a single fiber strength measuring machine analyzes the breaking strength of PAN fibers, founding that the higher the degree of crystallinity and degree of orientation of fibers, the greater the breaking strength, with respect to the degree of crystallinity and degree of orientation, grain size has little effect on the fracture strength of PAN precursor.Using scanning electron microscope (SEM) and small-angle X-ray scattering (SAXS) technique to characterize surface defects and interior nanometer micro holes of fiber, we can see that the fiber becomes dense and it’s diameter gets more and more small, the inside non-oriented circular hole gradually change to the alignment of the oval hole.Meanwhile this article also compares the differeces between the homemade precursor and the Japan precursor.the results show that orientation degree of homemade surpass Japanese precursor, indicate that homemade strand using larger initial drafting force will promote polymer chain extension and orientation.The lower crystallinity and the higher proportion of large voide volume of the homemade precursor,indicate that gel network skeleton will be damaged and produce more large-size flaw under larger initial drafting force.Grooves of homemade fiber surface generate in the spun fibers process and are retained to the precursor, however, surface of Japan PAN precursor is very smooth, indicating that wet spinning process of homemade precursor still exit problems in this respect.Significance of this study lies in the production of carbon fiber precursor with a systematic theory to guide, by optimizing process control to improve the quality of the microstructure of carbon fiber precursor, and produce more high quality carbon fiber material.