Studies of Hard Rubber Reactions VIII. The Corrected Coefficient of Vulcanization, and Its Upper Limit in the Accelerated Raw Rubber Compound

Abstract In a previous paper (J. Soc. Chem. Ind. Japan 40, 111B (1939)) it was shown that compounds containing up to 60 per cent of sulfur give coefficients of vulcanization higher than the theoretical maximum value of 47. Strictly speaking, however, the sulfur present in these cases can be divided into the following parts : sulfur soluble in acetone; (a) true elementary sulfur; (b) sulfur combined with organic matter; sulfur insoluble in acetone; (c) sulfur combined with rubber; (d) sulfur combined with resins and proteins; (e) metallic sulfide. In the present experiments, these five kinds of sulfur were separated as far as possible to determine the true or corrected coefficient of vulcanization, and its upper limit.