Tuning bio-inspired skin–core structure of nascent fiber via interplay of polymer phase transitions

Molecular simulations demonstrate how the skin–core structure of polymer fibers can be tuned for bio-inspired optimization of their mechanical performance.

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.

Study on the coagulation process of cellulose nascent fibers with ionic liquid AMIMCl as a solvent during dry-wet spinning

The coagulation process of nascent fiber of cellulose with ionic liquid 1- allyl-3-methylimidazolium chloride (AMIMCI) as the solvent was studied during drywet spinning. The diffusion rate and the crystallization situation of nascent fiber were tested, its fracture morphology was observed, and the diffusion coefficient D of solvent and the crystallization degree of nascent fiber were calculated according to relevant equations. The diffusion rate and diffusion coefficient of ionic liquid decrease with cellulose concentration increasing in spinning solution and then remain almost the same when the cellulose mass fraction reaches 7%. With the increase of coagulation bath concentration, the diffusion rate and diffusion coefficient of the solvents increase first and then decrease. When the coagulation bath concentration reaches 5%, the diffusion rate and diffusion coefficient of the solvents are at their maximum. With the increase of coagulation bath temperature and the length of air gap, the diffusion rate and diffusion coefficient of ionic liquid increase slightly. The cellulose solution concentration and the spinning air gap have an influence on the crystallization degree of nascent fiber. With the increase of cellulose solution concentration and the spinning air gap, the crystallization degree of the produced nascent fiber increases slightly, but the coagulation bath temperature basically have no influence on the nascent fiber formation.