Ozone degradation of vulcanized isoprene rubber as a function of humidity

Ozone degradation of vulcanized isoprene rubber was investigated by changing atmospheric humidity. Ozone exposure test of the vulcanized isoprene rubber was carried out with 50 pphm ozone at 40 °C, for 48 h under relative humidity (RH) between 20 and 90%, after a strain of 0.2 stretching. The degradation of the rubber was assessed by morphology observation with digital microscopy and rubbing test with a white swab. Black powders appeared on the surface of the rubber after ozone exposure test at more than 50%RH, while they did not at less than 50%RH. The severe ozone degradation of the rubber under high humidity condition was attributed to a generation of hydroxyl radical due to a reaction of water vapor and ozone.