DOI: 10.1615/ICHMT.2012.CHT-12
ISBN: 978-1-56700-303-1
ISSN: 2578-5486
SHELL FORMATION IN DRY SPINNING
ABSTRACT
A two-dimensional model of dry-spinning that employs a Newtonian rheology which depends on the local temperature and solvent concentration and accounts for the axial and radial distributions of temperature and polymer concentration, is presented. The model employs the leading-order equations for the fiber’s geometry and axial and radial velocity components derived from an asymptotic analysis of slender fibers at low Reynolds, Nusselt and Sherwood numbers, and two-dimensional equations for the temperature and solvent concentration fields. The diffusion of the solvent is assumed to depend on both the temperature and polymer concentration. The two-dimensional model presented here is an integro-differential boundary-value problem and is solved iteratively using as initial guess the solution corresponding to the leading-order equations of a non-isothermal fiber whose dynamic viscosity is constant. It is shown that a shell is formed at the fiber’s outer interface on account of the large increase in viscosity due to cooling and solvent evaporation. It is also shown that the fiber’s cooling may hinder the solvent diffusion but favor the polymer orientation.