Influence of radiation temperature on the crosslinking of nitrile rubber by electron beam irradiation

Nitrile rubber with 18% acrylonitrile content in presence and absence of polyfunctional monomers like trimethylolpropane triacrylate (TMPTA), tripropyleneglycol diacrylate (TPGDA), tetramethylolmethane tetraacrylate (TMMT) and m-phenylene bismaleimide was subjected to electron beam irradiations at different temperatures. The structural changes with different doses of radiations were investigated with the help of FTIR spectroscopy (in the ATR mode), dynamic mechanical thermal analysis and sol–gel analysis. There was a decrease in the concentration of olefinic groups for this elastomer on radiation at high temperature as compared to the room temperature. The increase in crosslinking at elevated temperature was also revealed by the increase in % gel content and dynamic storage moduli with radiation dose. The lifetime of spurs, an important criterion for overlapping of spurs, was determined for both grafted and ungrafted nitrile rubber using a mathematical model. The ratio of scissioning to crosslinking for nitrile rubber was determined using Charlesby–Pinner equation. The mechanical properties were studied and the tensile strength was found to increase with grafting of polyfunctional monomers on irradiation at high temperature.