Chemical Reactions during Vulcanization. III

Abstract

Abstract From the preceding discussion the following conclusions may be drawn: A. Vulcanization with Sulfur in General 1. Vulcanization with sulfur is fundamentally a chemical change involving activated sulfur and organic double bonds. 2. Sulfur must decompose from S8 (in the form of an eight-membered ring) to smaller molecular units, perhaps to S2 and S1 before it can be activated and react. 3. The ratio of atoms of sulfur combined to the number of double bonds lost is not restricted to one atom of sulfur for each double bond, but may have other values, which depend on the conditions and the reactions involved. B. Factice Formation 1. The rate of reaction of sulfur with tung and linseed oils is greatly influenced by small proportions of such agents as zinc oxide and mercaptobenzothiazole. 2. Combination of sulfur with the conjugated double bonds of the eleostearic acid in tung oil takes place at the terminal carbon atoms of the conjugated system, giving a typical 1,6-addition. 3. The following possible chemical reactions explain adequately the process of factice formation from tung and lineseed oil. Under different conditions different reactions predominate.