Studies on Nanocomposites of Ethylene Propylene Diene Rubber Chlorobutyl Rubber Blend for Gamma Radiation Environment

Abstract

Elastomeric materials have an important function in nuclear fuel reprocessing plants as o-rings, gaskets, airlock doors, hatches, master slave manipulators, radiation shields, etc. These components have to withstand the combined effect of gamma radiation and hydrocarbon solvents. Ethylene Propylene Diene Monomer (EPDM) rubber is the material of choice for elastomeric components in nuclear applications due to its radiations resistance. Though radiation resistance of EPDM is remarkable compared to other rubbers, its ability to endure hydrocarbon solvents used in reprocessing is low. To enhance the durability of EPDM in such environments, EPDM - Chlorobutyl rubber (CIIR) blends of varying compositions were developed and characterized for mechanical, thermal, and solvent sorption behavior. Spectroscopic and morphological analyses were used to evaluate the compatibility of blends. Due to synergistic effect, the optimal composition of blends with superior mechanical properties and solvent resistance were found to be 60-80% EPDM and 20-40% CIIR. The effect of gamma irradiation at three different cumulative doses (0.5, 1 and 2MGy) from 60Co source was studied on the optimized blends. Based on spectroscopic, morphological, mechanical, thermogravimetric and sorption properties of irradiated blends, the blend containing 80% EPDM was found to have superior retention of properties after irradiation. The blends were reinforced with organo-modified layered silicate (nanoclay) to further enhance their performance in radiation as well as hydrocarbons environments. The effect of nanoclay or layered silicates on mechanical and viscoelastic properties of EPDM-CIIR blends were studied in this thesis. The mechanical properties of the nanocomposites increased (upto 57 %) and solvent transport coefficients decreased (by 30%) with increasing nanoclay content. The morphology and physico-chemical interactions were evaluated by XRD, TEM and FTIR and correlated to the enhancement in mechanical properties.