IMPROVED OZONE RESISTANCE OF STYRENE-BUTADIENE RUBBER CURED BY A COMBINATION OF SULFUR AND IONIZING-RADIATION

Fourier Transform Infrared (FTIR) studies performed in this work indic ate that high ozone resistance of Styrene-Butadiene Rubber (SBR) formu lations cured by a combination of sulfur and ionizing radiation is ass ociated with unusually high vinyl concentration. On the other hand, su lfur cured SBR formulations with low vinyl concentration have poor ozo ne resistance. Curing with peroxides which involves chemistry similar to that of radiation curing, also leads to high vinyl concentration (r elative to sulfur curing) and high ozone resistance. Increasing the ab sorbed dose in sulfur-radiation cured samples decreased the high vinyl content to a point where the ozone resistance declined greatly. Carbo n black was shown to reduce the absorption of both the transvinylene a nd the vinyl unsaturation groups, but not to the same extent in all fo rmulations. Also, the carbon black seems to play a greater role in the absorption of the unsaturation as sulfur increases.