Influence of the network on the interaction parameter in system EPDM vulcanizate-solvent

Swelling measurements in six organic solvents were carried out on samples of dicumyl peroxide crosslinked ethylene–propylene–diene (EPDM) having various crosslink densities. The Flory–Huggins interaction parameter χ was determined for EPDM vulcanizates 312 and 812 as well as their mixture 312/812 using the Flory–Rehner equation. The results show that the χ parameter for the crosslinked polymer is greater than for the uncrosslinked one and is a linear function of the crosslink density. The swelling behavior of the networks were also interpreted by the Flory–Erman theory using the structural factor F4′ to characterize the network and its behavior during the swelling. The obtained χ values indicate that broadening of the molecular mass distribution, in the Gaussian region of distribution, mixture 312/812, increases interactions with solvents. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:991–999, 1997