Effect of radiation on mechanical properties and molecular structure of rubbers for nuclear robots

As polymers, rubber materials are easily affected by radiation; therefore, their radiation resistance must be considered for their use in robots and automation equipment in high-radiation environments. In this study, the properties of several common rubber materials, ethylene propylene diene monomer (EPDM), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluororubber (FKM), and acrylate rubber (ACM), were investigated under high-dose gamma-ray irradiation. The dose rate of gamma rays was 66.76 Gy/min, and the cumulative dose was 1214965.24 Gy. Oxidative decomposition of the double bond of EPDM occurred, leading to slight decreases in the strength and elongation. NBR and HNBR were mainly subjected to crosslinking of the molecular structure, resulting in small increases in strength and significant decreases in elongation. The cyano decomposition reaction occurred in ACM, and its crystallinity increased, leading to embrittlement and decreases in the strength and elongation. Oxidative decomposition and cross-linking simultaneously occurred in FKM, resulting in an increase in strength and decreases in elongation and the elastic modulus.

Kinetics and mechanism of oxidative decomposition of Congo red by Fenton’s reagent and its synergic effects on exposure to UV radiation

Congo red is a toxic azo dye which is used extensively in industries like textile, paper, pulp and paper. Very high amount of Congo red from these industrial sources is discharged into natural water bodies resulting environmental pollution. The present work reports the kinetics and mechanism of oxidative decomposition of Congo red by Fenton’s reagent in homogeneous medium and also under ultra violet light irradiation. Kinetic parameters like effect of [Fe2+], [H2O2], [Congo red] and temperature on the decomposition of Congo red were studied. The reaction is found to be fractional order with [Fe2+] and first order with [H2O2] and [Congo red]. The rate of oxidative decomposition of Congo red by Fenton’ reagent showed a rapid increase of three times when irradiated with ultra violet radiation and completion of reaction occurred within 5-6 minute. Various thermodynamic variables were determined and the presence of isosbestic points on sequential scanning of oxidation kinetics proves that the reaction is very smooth, spontaneous and endothermic. A suitable mechanism is suggested based on the experimental results obtained.