Investigation on the thermodynamic and kinetic parameters in the process of solvents transporting into EPDM crosslinking network at incremental temperatures

Abstract

The transport properties of cyclohexane, p-xylene and cyclohexanone in Ethylene Propylene Diene Monomer (EPDM) were determined by equilibrium swelling method, and the effects of temperature on the diffusion (D), adsorption (S) and permeation (P) behaviors were investigated. The results showed that the diffusion behaviors of cyclohexane, p-xylene and cyclohexanone in EPDM crosslinking network were not only related to the compatibility but also more significantly affected by temperature, and the swelling mechanism of EPDM crosslinking network was inferred. Fick diffusion contribution index (K_f) was obtained by Peppas-Sahlin model, and the D and P values of the three EPDM swelling systems could be correlated by the same D ∼ K_f relationship and P ∼ K_f relationship, respectively. The temperature dependance of the D and P values of EPDM/cyclohexane and EPDM/p-xylene system was less at low-temperature and higher above 35 ℃. The diffusion (E_D) and permeation activation energies (E_P) determined for the EPDM/p-xylene swelling system showed the lowest values, corresponding to the highest D and P values, that is, the diffusion and permeation of p-xylene in EPDM was very fast. This work can provide an important guiding significance for evaluating the liquid resistance of EPDM-based industrial and automotive rubber products.