An effective way to control the radical reaction and its mechanism in EPDM under γ-ray irradiation

The effects of a compound that contains a xanthate group named DIP on the radical reactions and structural evolution of the ethylene propylene diene monomer (EPDM) were investigated. It was found that the structural evolution and long-term stability of the EPDM can be realized by controlling the radical reaction in the matrixes of EPDM during γ-ray irradiation. The results show that the DIP can prevent EPDM deterioration, when the γ-ray irradiation dose reaches 450 kGy, the retention rate of the elongation at break and tensile strength of the EPDM samples containing 1 wt% DIP could remain about 90% and 160%, while those of additive-free EPDM are only about 33% and 70%. On the other hand, the thermal stability of the EPDM samples decreases markedly with the dose increasing under γ-ray irradiation. However, the thermal decomposition temperature of the EPDM samples containing DIP remains basically unchanged after irradiation, and DIP can also improve the oxidation resistance of the EPDM. Electron spin resonance studies reveal that DIP can effectively control the radical reactions inside the EPDM during γ-ray irradiation. Rheology results show that the structural evolution of the EPDM can be well controlled under γ-ray irradiation owing to the presence of DIP in the EPDM matrixes. Density functional theory calculations indicate that the reversible radical reactions inside EPDM/DIP systems are crucial in realizing the long-term stability and controllable structural evolution of the EPDM under γ-ray irradiation.