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Two new methods for determining Hansen's three-dimensional solubility parameters (3DSP) for lightly crosslinked polymers are presented and evaluated using commercial glove materials composed of butyl, natural, nitrile, and neoprene rubber. In the first method, the polymer 3DSPs are determined from a weighted average of the 3DSPs of a range of organic solvents, where the weighting factor is the product of the solvent molar volume and the fractional uptake of the solvent measured by immersion testing. The resultant polymer 3DSPs were used to model solvent uptake via the Hildebrand–Scott and modified Flory–Rehner expressions for the Flory interaction parameter. After grouping solvents of similar structure and applying an additional weighting factor, estimates of equilibrium solubility within a factor of two of experimental values were obtained for 176 of the 212 (83%) solvent–polymer combinations examined. In the second method of estimating polymer 3DSPs, the Flory interaction parameters for all solvent–polymer pairs are determined at the outset via the modified Flory–Rehner equation and used to solve for the polymer 3DSP values by multiple nonlinear regression. Solubility estimates are then back-calculated. This method provided different values of the 3DSPs for the polymers, including negative δp values for the butyl and natural rubber. However, the accuracy of solubility estimation was comparable to that obtained using the weighted-average method without the need for any adjustable factors. The advantages of these alternative methods over the graphical method for obtaining reliable estimates of the 3DSPs of lightly crosslinked polymers are discussed. This is the first demonstration of a general 3DSP-based approach to quantitative solubility modeling in polymer–solvent systems. © 1996 John Wiley & Sons, Inc.

The most widely accepted method for determining Hansen's three-dimensional solubility parameters (3DSP) for crosslinked polymers entails graphically estimating the center of a spherical region in 3DSP-coordinate space whose boundaries are defined in terms of the extent of swelling by solvents whose 3DSP values are known. In this article, the results of immersion tests performed at 25°C with 53 solvents on each of four commercial polymeric glove materials are used to critically evaluate this method. Analyses reveal a number of serious shortcomings with respect to the reliability of 3DSP estimates obtained. In the context of modeling solubility or other measures of solvent–polymer compatability, it is recommended that alternative methods be sought for determining 3DSPs for crosslinked polymers. © 1996 John Wiley & Sons, Inc.