Improved ozone resistance of styrene-butadiene rubber cured by a combination of sulfur and ionizing radiation

Abstract

The ozone resistance of filled styrene-butadiene rubber (SBR) samples, cured by a combination of sulfur and ionizing radiation, was investigated. The ozone resistance of similar filled samples, but fully cured by sulfur or peroxide, was also studied. The influence of the filler (carbon black) on the optical density measurements of these SBR formulations was investigated. In addition, the influence of the absorbed dose on the ozone resistance for samples with formulations containing partial levels of sulfur was determined. Fourier-transform infrared studies performed in this work indicate that the high ozone resistance of SBR formulations, cured by a combination of sulfur and ionizing radiation, is associated with unusually high vinyl concentration. On the other hand, sulfur cured SBR formulations with low vinyl concentration have poor ozone resistance. Curing with peroxides, which involves chemistry similar to that of radiation curing, also leads to high vinyl concentration (relative to sulfur curing) and high ozone resistance. Increasing the absorbed dose in sulfur-radiation cured samples decreased the high vinyl content to a point where the ozone resistance declined greatly.