Synergistic enhancement of mechanical,viscoelastic, transport,thermal, and radiation aging characteristics through chemically bonded interface in nanosilica reinforced EPDM-CIIR blends

The study investigates the influence of bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) grafted nanosilica (NS) reinforcement on the mechanical, viscoelastic, thermal, and transport characteristics as well as behavior after exposure to different cumulative γ-radiation doses of EPDM-CIIR blends for application in nuclear and hydrocarbon environments. The tensile strength and modulus of the nanocomposites were enhanced upto 64% and 118%, respectively whereas solvent diffusion coefficient reduced by 22%. The degradation onset temperature improved from 485°C for unfilled blends to 503°C for the nanocomposites. γ-radiation aging resistance of EPDM-CIIR blends improved with incorporation of nanosilica, with blends containing 7.5phrNS showing optimum properties and radiation aging resistance. The property improvements are attributed to the dispersion of NS and chemically interfaced covalent linkages between SiO₂-EPDM/CIIR chains that provides large interfacial area for effective stress transfer and creates barrier to free radical and solvent permeation. The applicability of Korsmeyer-Peppas, Peppas-Sahlin, and Higuchi models to predict of sorption behavior are investigated. Coats-Redfern and Horowitz-Metzger models were employed to evaluate the activation energy for thermal degradation. Slight decline in properties at higher nanofiller contents was due to the formation of agglomerates. TEM, FTIR, and rheological curves were utilized to corroborate these observations. FTIR and ESR analysis provided insight on the chemical changes in the nanocomposites after irradiation.