The construction of a phase diagram for a ternary system used for the wet spinning of acrylic fibers based on a linearized cloudpoint curve correlation

A phase diagram for the commercially significant ternary system poly(acrylonitrile-co-methylacrylate-co-sulfonic acid), sodium thiocyanate, and water, used to wet-spin textile acrylic fibers, was constructed from a linearized cloudpoint curve correlation. Experimental cloudpoints in the accessible low polymer content range were evaluated and used to extrapolate to higher polymer concentrations to produce a full-phase diagram. Although the correlation only holds for systems undergoing liquid/liquid demixing, the fact that the relation holds for this system despite evidence for PAN crystallization is discussed. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2131–2139, 1997