Characterization On The Structure And Mechanical Properties Of Polyacrylonitrile Precursors On Different Draw Stages

Polyacrylonitrile (PAN) has been thought to be one of the most importantprecursors to make the high performance carbon fibers. The quality of thePAN precursors could strongly effect on the properties of the carbon fibers.Therefore, it is obviously very important to study the relationship between themicrostructure and the high-performed properties of the precursors. This maybe the key issue to improve the quality of the carbon fibers.In this study, a systematic study of the PAN precursors were studied byusing the combinations of the experimental techniques which includes X-raypowder diffraction and pole figure, sound velocity method, birefringencemethod, Scanning Electron Microscopy (SEM), Fourier Transform InfraredSpectroscopy (FTIR), and single fiber tensile test.The results indicated that as the draw ratio increased, the crystallinedegree, the orientation degree and the mechanical properties of the PANprecursors have also been improved. Drawing was thought to be one of thekey processes to improve the mechanical properties of the PAN precursors.The orientation distribution function q(x) calculated from the Pseudo-affine deformation theory was in good agreement with the experimental data N(x).The p and q values in the effective draw ratio were 0.49 and 0.98 respectively,which indicated that the second stage of drawing was more important on theformation of the orientation structure than the first one. Overdrawing could beavoided to decline of the mechanical properties of the PAN precursors.