Exploring the effects of non-solvent concentration, jet-stretching and hot-drawing on microstructure formation of poly(acrylonitrile) fibers during wet-spinning

The simultaneous effects of non-solvent concentration in the spinning dope, jet-stretching and hot-drawing on porosity, morphology development and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. Addition of non-solvent to the spinning dope increased dope viscosity, the entanglement density of the polymeric solution and the number of entanglements per chain. Drawability of the as-spun fiber depended on the number of entanglements per polymer chain. Therefore, addition of non-solvent improved or spoiled drawability of the wet-spun fibers based on the concentration of the initial spinning dope. Hot-drawing and jet-stretching did not affect the fraction of nanovoids but shifted their size distribution towards smaller values. However, hot-drawing was more effective in reducing the overall porosity of the fibers in comparison with jet-stretching. Fiber tenacity increased when overall porosity decreased. Finally, strength-diameter correlation showed good agreement with the Griffith's theory.