THE USE OF RADIOACTIVE TRACERS IN RUBBER RESEARCH 590184
Because of the importance of sulfur in rubber chemistry, the beta ray emitting isotope sulfur-35 has been especially useful in extending the unique advantages of tracer methods and techniques to rubber research. Problems connected with the solubility of sulfur or sulfur containing compounds in rubber mixtures, migration, and “blooming” or surface crystallizing tendencies can all be most readily investigated in the laboratory by means of radioactive sulfur. The use of tagged sulfur in an unvulcanized rubber mixture is the basis for a very convenient laboratory method for determining the amount of sulfur which combines chemically with the rubber during vulcanization. Tagged sulfur and sulfur compounds have been employed to provide new information for interpreting the complicated chemical reaction mechanisms involved in rubber vulcanization and to characterize the type of sulfur-rubber compounds which are formed. Extensive Russian publications in this field have emphasized the applicability of isotope exchange reactions for studying vulcanization.
Carbon-14 tagging has been used for diffusivity measurements to investigate the segmental motions and internal frictional forces for rubber molecules. But the use of carbon-14 in rubber research has been much more limited than that of sulfur-35 and the potentialities for securing new and useful information through tagging with carbon-14 have by no means been fully realized.