Dry Spinning of Polymer Fibers in Ternary Systems

Abstract

Part I: Model Development and PredictionsThis paper addresses the development and application of a two-dimensional, three component model for the dry spinning process of polymer fibers. The model presented is an expansion of a previously developed two-component dry spinning model [1] that incorporated both viscous and viscoelastic effects in the constitutive equation for the spin fluid, along with two-dimensional effects to account for radial variations in the fiber temperature and composition profiles along the spin line. The model presented in this paper includes the effects of water in the spin dope through incorporation of the diffusion equations for ternary mass transfer. Mass and energy balances on the gas side are also taken into account so that the effects of ambient conditions can be investigated. Calculations are based on the system: cellulose acetate-acetone-water. Results are presented for profiles of solvent concentration, temperature, and glass transition temperature profiles for typical industrial operating conditions. Force and stress distributions in the fiber at various points along the spinline, analyzed in terms of contributions from the viscoelastic and viscous terms in the constitutive equation, illustrate the role of these stresses in the freezing in of structure along the spinline. Model predictions are shown to be in good agreement with the principal characteristics of dry spinning.

Dry Spinning of Polymer Fibers in Ternary Systems

“…With the exception of die swell described in the next section, model calculations presented in this paper are based on the equations and algorithms described in Part I [2].…”

“…In Part I of this work [2], a two-dimensional dry spinning model was developed for ternary solution spinning solutions. The predictive ability of the model suggests that it can be used to compare to actual spinline data.…”

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In this work, predictions based on the 2D dry spinning model developed in Part I of this work [2] along with a die swell subroutine supplied by an industrial company, are used to compare with fiber concentration and elongation to break data from an industrial spinline. Die swell ratio predictions agree well with measured values and solidification along the spinline is shown to be due to homogeneous glass transition in the absence of phase separation.

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Simulation of dry‐spinning process of polyimide fibers

“…Recently, the work on dry‐spinning by Gou and McHugh12, 13 presented a modified model with viscoelasticity as well as solidification mechanism. They also developed a two‐dimensional model in ternary system, giving more detailed simulation of CA/acetone/water spinning solution 14, 15. For PAA/DMAC spinning system, water mass fraction is less than 0.3%, so a binary system is adapted for dry‐spinning model in this article.…”

Simulation of polyimide fibers with trilobal cross section produced by dry-spinning technology

“…This model accounts for the viscoelastic nature of the polymer as well as the solidification mechanism of fibers. They also developed a two‐dimensional model in a ternary system that better details the CA/acetone/water spinning solution .…”