EPR studies on the interaction between additives and polyethylene matrix initiated by gamma radiation

Silane cross-linked polyethylene (PE) modified with two antioxidants (Irganox 1076 and Irganox PS802) and aluminum hydroxide (ATH) as a flame retardant, was irradiated with gamma rays at 77 K. The radical processes initiated by radiation were investigated by Electron Paramagnetic Resonance (EPR) spectroscopy from 100 K to the temperatures at which the spectra disappeared. Interpretation of the experimental signals was proposed. The mechanism of the two-stage action of phenolic antioxidant on PE was suggested on the basis of EPR spectra of individual components. It was found that paramagnetic defects generated by radiation in ATH decayed in parallel and independently of radical processes in PE matrix due to phase separation. Thus, in contrast to antioxidants, they did not affect the degradation of the PE matrix. The decrease in concentration of ATH defects in the range of100-190 K was more efficient in the dispersed phase of the polymer composite than in the microcrystalline ATH powder.