Study on the application of Flory–Huggins interaction parameters in swelling behavior and crosslink density of HNBR/EPDM blend

The sorption and permeation coefficients of four amine solvents in hydrogenated nitrile rubber/ethylene propylene diene monomer rubber (HNBR/EPDM) blends were calculated, and the transport mechanism of solvents was verified by the Peppas–Sahlin model. The Flory–Huggins interaction parameters (χ: χ1D and χ3D) between solvent and HNBR/EPDM blend were obtained by one-dimensional solubility parameter (SP-1D) and three-dimensional solubility parameter (SP-3D), respectively. The predictive powers of χ1D and χ3D on the transport behavior of amine solvents permeating in HNBR/EPDM blends were studied and compared. The application of χ1D and χ3D in the calculation of cross-linking density was explored. It is found that the χ3D is more suitable for predicting the transport behavior of solvents with both strong and weak polarity in the blends, while the χ1D is only available for the solvents with poor polarity. However, the χ1D is more appropriate to calculate the crosslink densities of HNBR/EPDM blends.