Ozone Ageing of Silicone Rubber and the Effects of Anti-Oxidants on the Ozone Ageing of Nitrile Rubber.

摘要

Work done by others suggested that a rapid loss of physical properties could occur in silicone rubbers when subjected to high concentrations of ozone. Experiments have now been carried out using a Hampden P3 C6 ozone cabinet to evaluate the significance of this evidence when the material is used in the face masks worn by RAF air-crews at high altitudes, where the ozone concentration can reach relatively high levels. No loss of physical properties was found over the duration of the experiment. The effect of ozone attack on nitrile rubber was also investigated. The effectiveness of four anti-oxidants used as anti-ozonants at an ozone concentration of 50 pphm (parts per hundred million) was studied together with a commercial nitrile rubber seal material. It was found that the anti-oxidants were effective anti-ozonants when compared with the unprotected rubber, whereas the commercial formulation had relatively poor resistance to ozone. The effect of varying the tensile strain applied to the samples was also considered and indicated that in general a lower strain resulted in a smaller drop in physical properties. The effect was not very marked.