| Abstract: | An investigation of the diffusion competition between solvent and nonsolvent in a coagulation bath is presented for the formation of a new cellulosic fiber by wet-spinning. The system consisted of the spinnable cellulose solution with a mixture of liquid ammonia/ammonia thiocynate as the solvent and low-molecular-weight alcohols as the nonsolvents. The diffusion competition between solvent and nonsolvent was quantitatively characterized in terms of their mass transfer rate differences. The measurements of this rate difference were performed on the model filament shaped from gelled cellulose solutions. Results revealed that an increase in molecular size of coagulant, bath temperature, and coagulant concentration in the bath enhanced preferential diffusion of solvent from cellulose solution. Fiber spinning experiments showed that a higher value of the initial modulus of the fiber was attained with a coagulation condition providing a lower value of mass transfer rate difference. The importance of mass transfer rate difference was also shown in the influence of the fiber cross-sectional shapes. |
