초록
The critical concentrations for high tensile strength and modulus polyacrylonitrile(PAN) were measured on dimerhylformamide solution of PAN's which had various kinds of average molecular weights. These critical concentrations decreased with increasing molecular weight and were nearby placed at the same viscosity regardless of molecular weight. The PAN films were cast from the solution of critical concentrations. Two kinds of uniaxially drawn films were prepared; one was drawn in boiling water and the other was drawn in dry heat again artier drawn by 3 limes in boiling water. The structures of the drawn films were investigated by X-ray dinractometer, thermomechanical analysis, dynamic mechanical analysis, and tensile measurements. From this study, it has been found that the larger the molecular weigh of PAN increases, the higher the draw ratio is required to cause the crystallization upon drawing together with the increase in fibrillization of film surface. The degree of the overall crystallization and the molecular stress and internal defects in amorphous region increased with increasing molecular weight of PAN.