Ozone Attack and Antiozonant Protection of Vulcanized Natural Rubber. A Surface Study by Attenuated Total Reflectance Spectroscopy

Abstract

Abstract This work reports a direct surface analysis of ozonization of vulcanized NR compounds by ATR. On ozonization of a vulcanized NR compound without clay filler or AO a degraded rubber layer, which contains ozonides and carbonyl compounds, is formed on the surface. This reaction is considerably slower than that of raw NR. When clay filler is added, the first effect is a decrease of rubber on the surface and a corresponding increase in the surface concentration of clay. With further ozone exposure, ozonides and carbonyl compounds appear. When a compound containing N,N′-dioctyl-p-phenylenediamine AO is ozonized, a film is seen, which has an ATR spectrum essentially identical to that of the ozonized liquid AO. There is no evidence of ozonized NR products, or of complex reaction products between AO and ozonized NR. These results are consistent with a scavenger or protection-layer mechanism for antiozonant protection.