Effect of expanded graphite on thermal, mechanical and dielectric properties of ethylene–propylene–diene terpolymer/hexa fluoropropylene–vinylidinefluoride dipolymer rubber blends

Expanded graphite (EG) filled with compatibilized and uncompatibilized EPDM/FKM (50/50, w/w) blends were prepared by two-roll mill mixing. Maleic anhydride grafted EPDM (MA-g-EPDM) is used as a compatibilizer. The cure characteristics, filler dispersion, mechanical properties and DC electrical conductivity of the composites were evaluated. The thermal stability of the EG loaded EPDM/FKM blends was studied using thermogravimetric analysis (TGA). The activation energy of the composites was evaluated by the Coats–Redfern method. The microwave properties like dielectric permittivity, dielectric loss, conductivity, dielectric heating coefficient and absorption coefficient were evaluated. At higher EG loading, the optimum cure time (T90) decreases due to the increased thermal transition of the blends in presence of EG. The tensile properties of all the composites, especially those with compatibilizer, increased with aging. The AC and DC conductivities increase with increase in EG loading, due to the formation of enhanced conductive networks by EG platelets. The flammability and thermal characteristics are improved by the addition of EG. The morphology of the composites was investigated using scanning electron microscopy (SEM).

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► At higher EG loading, optimum cure time decreases.
► The tensile properties of compatibilized blends increased with aging.
► The AC and DC conductivities increases with increase in EG loading.