Porous fiber formation in polymer-solvent system undergoing solvent evaporation

Pratyush Dayal, Thein Kyu
2006 Journal of Applied Physics  
Temporal evolution of the fiber morphology during dry spinning has been investigated in the framework of Cahn-Hilliard equation ͓J. Chem. Phys. 28, 258 ͑1958͔͒ pertaining to the concentration order parameter or volume fraction given by the Flory-Huggins free energy of mixing ͓P. J. Flory, Principles of Polymer Chemistry ͑Cornell University Press, Ithaca, NY, 1953͒, p. 672͔ in conjunction with the solvent evaporation rate. To guide the solvent evaporation induced phase separation, equilibrium
more » ... ion, equilibrium phase diagram of the starting polymer solution was established on the basis of the Flory-Huggins free energy of mixing. The quasi-steady-state approximation has been adopted to account for the nonconserved nature of the concentration field caused by the solvent loss. The process of solvent evaporation across the fiber skin-air interface was treated in accordance with the classical Fick's law ͓R. B. Bird et al., Transport Phenomena ͑J. Wiley, New York, 1960͒, p. 780͔. The simulated morphologies include gradient type, hollow fiber type, bicontinuous type, and host-guest type. The development of these diverse fiber morphologies is explicable in terms of the phase diagram of the polymer solution in a manner dependent on the competition between the phase separation dynamics and rate of solvent evaporation.
doi:10.1063/1.2259812 fatcat:ilzm6c3lmjffdi6miphr4zasbe