The surface oxidation of a thermoplastic olefin elastomer under ozone exposure: ATR analysis

Abstract

The ozone oxidation on the surface of a thermoplastic olefin elastomer (TPO) under different ozone concentrations, exposure times, and strain ratios has been studied using attenuated total reflection infrared spectroscopy (ATR). More EPDM materials are found on the surface of the TPO than in the bulk. Carbonyl, carboxyl, CC, and OH groups are formed under ozone exposure but OH groups appear only at the surface layer. The carboxyl and carbonyl groups can extend from the surface to more than 1.4 μm deep into the TPO and have different distributions with respect to penetration depth. Applied stress increases the oxidation rate and has the greatest effect on the outermost surface layer because it enhances the oxidation rate of the vulnerable surface groups. Increase in ozone concentration also accelerates the oxidation rate and produces much greater amounts of carbonyl groups than the strained specimen. Attack on CH 2 groups occurs only after a long exposure time and at a high ozone concentration.