Study on the Prediction Model of Swelling Response of EPDM in Liquid Mixture by Using the Modified Flory–Huggins Interaction Parameter (χHSP)

ABSTRACT The swelling responses of ethylene propylene diene monomers (EPDM) in cyclohexane/xylene (CYH/X) and cyclohexane/cyclohexanone (CYH/C) binary systems were studied by using equilibrium swelling method, and the co‐solvent effect was further analyzed. The results show that the swelling responses of EPDM in CYH/X and CYH/C binary systems are significantly different. EPDM exhibits more obvious co‐solvent effect in CYH/C binary system which may be generated by the self‐association of cyclohexanone. In addition, the modified Flory–Huggins interaction parameter ( χ HSP ) calculated by three‐dimensional solubility parameters (HSP) was used to establish the prediction model from the correlation with the swelling ratio ( q m ) of EPDM. The prediction model can be represented by an exponential equation with high degree of fitting, and the calculated q m values from this model are comparable with the experimental values. The prediction model has been employed to evaluate the swelling responses ( q ‐fitting) of EPDM in IRM 903 test oil/ethanol mixtures theoretically. It reveals that lower χ HSP values result in higher swelling responses of EPDM, following the same rule of q – χ HSP . Potentially, the prediction model based on χ HSP provides a new way to determine the swelling responses of EPDM based rubber parts in any possible fluids.