Effect of nanoclay and nanosilica on carbon black reinforced EPDM/CIIR blends for nuclear applications

Elastomeric components used in nuclear reprocessing plants have to withstand the combined effect of radiation exposure and hydrocarbon ageing. For such applications, EPDM/CIIR blends were reinforced with varying amounts of nanoclay and nanosilica along with carbon black. The effect of nanofiller type and content on mechanical properties, compression set and solvent sorption coefficient for hybrid nanocomposites were evaluated and compared with carbon black filled compound. Both nanofillers enhanced the mechanical properties while reducing the solvent permeation. Nanocomposites with 10 phr nanoclay had the highest strength. Studies on Payne effect in hybrid nanocomposites confirmed the interaction between nanofillers and rubber matrix that enhanced mechanical properties. The dispersion of nano and micro filler was analysed with transmission electron microscopy (TEM). The test specimens were exposed to cumulative doses of 500, 1000 and 2000 kGy gamma-radiation. Both chain scission and crosslinking of polymer chains occurred upon irradiation. The percentage change in mechanical properties upon ageing was least for ternary composites with 5 phr nanoclay and 10phr nanosilica. The creation of tortuous path on incorporation of nanoparticles in the blend decreased solvent permeation and free radical migration resulting in reducing the ageing effects in the hybrid nanocomposites. FTIR and ESR spectra provided insight on chemical changes and presence of free radicals after irradiation.