Decrease in the performance of a phenolic antioxidant in preparation of inhibited polyethylene films by hot pressing

Resumo

The effect exerted on the efficiency of the polymer inhibition by the conditions (pressure, treatment time, antioxidant concentration) of preparing films of polyethylene with Irganox 1010 phenolic antioxidant by hot pressing was studied. Blends of the antioxidant with the polymer were prepared by treatment of the binder particles with a solution of Irganox 1010 in acetone. After drying to remove the solvent, films were prepared from the dry blends by hot pressing. The films were subjected to oxidation in the molten state in air. Evolution of the characteristic IR absorption bands of the antioxidant and polymer was monitored. The inhibition efficiency was evaluated by the induction period of the film oxidation. Two interrelated processes occur concurrently in the course of hot pressing: sorption uptake of the antioxidant, resulting in its more uniform distribution in the bulk of the sample, and a decrease in the relative content of hydroxy groups, i.e., partial degradation of the inhibitor. The latter process can decrease the efficiency of the polymer inhibition. Therefore, in development of polymer compounds with enhanced oxidation resistance, it is necessary to optimize the process conditions, namely, the composition of the ingredients, the procedure for introducing the antioxidant, and the temperature and time of sample preparation.