Gamma‐radiation stabilization of polypropylene

Abstract

Abstract Especially synthesized compounds, together with conventional antioxi‐dants, were evaluated as radiation stabilizers of isotactic polypropylene. Electron spin resonance (ESR) determinations of free radical populations in stabilized and unstabilized samples were carried out after irradiation and at periods of up to 460 h. The same samples were mechanically tested and a correlation was found to exist between the concentration of trapped peroxy radicals and the radiation deterioration in the polymer. Post‐irradiation effects were evaluated using accelerated aging at 70°C and carbonyl index determinations at periods of up to 110 days indicated that some of the stabilizers examined are efficient inhibitors of post‐irradiation oxidation. The results are discussed in the light of the free radical mechanism of the radiation‐induced auto‐oxidative degradation of polymers.