DIMETHYLACETAMIDE SORPTION KINETICS IN A URETHANE UREA ETHER BLOCK-COPOLYMER

Polymer solvent interactions in a block polyurethane/urea/ether polymer belonging to the spandex family are considered in this article. Independent analysis of the sorption isotherms for dimethylacetamide (DMAc) in the spandex polymer as a function of vapor activity and temperature were presented in a previous article. A second aspect in understanding solvent/polymer interactions is the kinetics of desorption. Characterization of the solvent devolatilization is an important aspect of the drying procedure to guide processing protocols to eliminate residual solvent in the final spandex products, especially for medical applications [E. Hicks, A. Ultee, and J. Drougas, Science, 147, 373 (1965); J. W. Boretos and W. S. Pierce, J. Biomed. Mater. Res., 2, 121 (1968); P. M. Knight and D. J. Lyman, J. Membr. Sci., 17, 245 (1984) 1. This article reports data for desorption kinetics under nominally isothermal conditions to provide diffusion coefficients as a function of polymer phase concentration and temperature. Desorption curves were found to be Fickian at least up to the half-time of desorption. Diffusion coefficients were therefore calculated using a half-time method. Temperature effects upon sorption or desorption were measured to obtain corrected diffusion coefficients and found to be significantly different than the apparent diffusion coefficient measured from a conventional McBain sorption cell. (C) 1994 John Wiley & Sons, Inc.