IV—A Theory of Vulcanization of Rubber

Abstract

THE vulcanization ofrubber has always been a much discussed enigma. The progress of its practical application has been rapid and the quality of manufactured rubber articles

Crystallization of Vulcanized Rubber

“…A number of writers, basing their conclusions on different types of experiments, have discussed the minimum amount of sulfur required for vulcanization and have attempted to assign to it a numerical value. For example, in presenting a theory of vulcanization, Boggs and Blake (5) claim that 0.5 per cent combined sulfur is necessary and sufficient for the formation of pure soft vulcanized rubber. Bruni (6) presented tensile data for a series of compounds employing sulfur and an ultra-accelerator.…”

The Sulfurization of Unsaturated Compounds.

“…There is, for example, the belief of Kirchoff (42) that the end group on the rubber hydrocarbon is a ring which opens to give an active methylene group and that the first step of vulcanization occurs there by cross-linking of the chains. Boggs and Blake (5) concluded from a study of the heat of combustion of vulcanized rubber that Kirchoff was right, and Hauser and Sze (33) also accepted bridging at the terminal carbons as the explanation of soft rubber. The latter investigators also considered saturation of the double bonds in the middle of the chains the process which forms ebonite.…”

VULCANIZATION OF RUBBER Vulcanization of Rubber

“…Boggs and Blake (9) assume that there are two types of unsaturation in rubber; that the saturation of one type (the end double bonds) gives soft rubber, and that of the other type (the remaining double bonds), hard rubber; and that both reactions go on at the same time. They base their theory chiefly on the amount of heat produced in the reactions.…”