On the mechanism of ionizing radiation damage in SBR elastomers

Abstract

Studies were made to provide information for use in the development of SBR elastomers with improved resistance to attack by high energy radiation. Changes of molecular structure were investigated by viscometric techniques and by measuring gel content. Chemical changes were followed by use of infrared spectrophotometry. Results indicate that the polymer in toluene, when subjected to radiation doses in the range 0–100 Mrep, is randomly scissioned. When similarly treated in chloroform, the polymer is initially randomly crosslinked and then the newly formed elastomer network undergoes random scission. The nature of the end chemical changes is shown to depend on environmental factors. In the presence of a limited supply of oxygen, the polymer is partially oxidized. The oxidation reaction appears to have no influence, however, on the random nature of the degradation process. The external butadiene structures are shown to be attacked more rapidly than the internal groups. The phenyl rings of the styrene groups in the polymer molecules, on the other hand, are only moderately affected in this respect. The results obtained in these solution studies are used to predict the effects of radiation damage to SBR vulcanizates.