Orientation Structure and Mechanical Properties of Polyacrylonitrile Precursors

The microstructure of the polyacrylonitrile (PAN) precursors can strongly affect the structure of the carbon fibers which determine the final mechanical properties of carbon fibers. The orientation factors ( n f ) of PAN precursors under different draw ratios were characterized by the birefringence ( n f ), which was obtained through polarized microscopy. The results show that the increasing of the draw ratio may enhance the degree of orientation, which can correspondingly improve the mechanical properties. However the increasing speed of the orientation factor slows down as the draw ratio reached to 8.