Diffusion coefficients of Dimethyl sulphoxide (DMSO) and H2O in pan wet spinning and its influence on morphology of nascent polyacrylonitrile (PAN) fiber

Wetspun nascent PAN fibers were immersed into a DMSO/H2O coagulation bath. Diffusion of DMSO from nascent fiber and that of H2O into nascent fiber were studied at different temperatures and concentrations of coagulation bath. The diffusion coefficient of H2O is larger than that of DMSO. As the coagulation bath temperature increased, the diffusion coefficients of DMSO and H2O increased. Diffusion activation energy of DMSO is smaller than that of H2O during the diffusion. Cross sectional and surface structure of nascent PAN fiber were observed in relation to coagulation ability (the product of diffusion coefficients of two solvents). Coagulation ability was found to have a significant influence on both the cross sectional and surface morphology of nascent fiber. To obtain nascent fiber with circular cross sectional and smooth surface morphology, coagulation ability should be controlled at low value.