Elastomer Swelling in Mixed Solvents

A critical performance factor for elastomers in chemical service is absorption of solvents. Since swelling data are often limited to single component exposure, methods to estimate elastomer compatibility with mixed solvents have received considerable theoretical attention. The evolution of these methods is reviewed. Then, an alternative empirical procedure is proposed which is based upon a generalization of Flory's network-solvent phase equilibrium concept. The resulting linear and nonlinear partition coefficient models are used to predict swelling behavior of various elastomers in nearly ideal hydrocarbon solutions as well as other non-ideal solutions. Advantages of the current methods are that they utilize readily available swelling data of the elastomers in pure solvents and also thermodynamic data of the solution of interest. Adjustable parameters are required only when strong associative swelling agents are present. Finally, information regarding the chemical structure of the elastomer is not required.