Effect of spinning speed on microstructures and mechanical properties of polyacrylonitrile fibers and carbon fibers

The effect of spinning speed on the microstructures and mechanical properties of polyacrylonitrile (PAN) fibers and carbon fibers was investigated. The microstructures and mechanical properties of PAN fibers and resulted carbon fibers were characterized. When winding speed increased from 63m/min to 95m/min, the fibers still exhibited smooth surfaces, and the diameter and aspect ratio of fibrils increased. In early spinning stages, the lamellae were arranged orderly and PAN fibers had larger crystallinity at low spinning speed. After densifying process, the crystal layers were stacked regularly and their crystallinity was larger at high spinning speed, and the resulted precursor fibers had big thermal stability and large dimethylsulfoxide (DMSO) residue value. Meanwhile, the tendency of mechanical strengths of PAN fibers was in accord with their crystallinity changes. Increasing spinning speed brought the negative influence on microstructures and mechanical properties of the resulted carbon fibers, and the carbon fibers owned low tensile strength due to relatively poor crystallinity and graphitic structures.