Abstract
In order to elucidate the coagulation mechanism for the polyacrylonitrile/HNO₃ (solvent)/H₂0(nonsolvent) wet-spinning system, the effects of the coagulation bath temperature and composition (content of solvent m the bath) on the coagulation behavior, and hence structure and properties of the resulting(proto and drawn) fibers have been investigated prior to finding out the optimum(critical) bath composition. Apparent diffusion coefficients of solvent at different coagulation conditions have been estimated from diffusing-out experiments during the coagulation step using Takeda's simplified model based on quasi-binary, equimolar diffusion. The changes in structure and properties of the fibers caused by the variation of the diffusion coefficient at different coagulation conditions have been confirmed from the experiments on mechanical properties, dye sorption, and morphological structure of the fibers.