Visualization of the Thermal Oxidation of Polyethylene Containing Phenolic Antioxidant

Abstract

Here, we investigated the thermal oxidation process of a phenolic antioxidant in polyethylene ( PE ) by using FT - IR imaging. The peaks of the phenolic group of the antioxidant change by being oxidized with a higher sensitivity than the carbonyl group peak in the FT - IR spectra. Thus it became possible to visualize the oxidation process of PE in more detail. Samples of PE containing a phenolic antioxidant were being kept in air at 60 ° C for up to 11300 hours, and the following results were obtained. ( i ) The antioxidant inside PE was not oxidized. ( ii ) The antioxidant di ff used from the inside of PE to the surface, where it was oxidized. ( iii ) The oxidation started at the surface of PE and the speed of oxidation inside PE was very high because of the low concentration of the antioxidant.