Vulcanization of Rubber by Means of Resins
Abstract Vulcanization has been the subject of much careful research since its discovery by Goodyear in 1840. Originally “vulcanization” meant a treatment of rubber with sulfur and heat, but now the word has a much broader connotation, since it has been discovered that numerous substances can produce the same effect as sulfur. Vulcanization is the process by which rubber passes from the predominantly plastic state to a predominantly elastic state by means of an irreversible transformation. This phenomenon is due to the formation of intermolecular bridges, leading to a more or less dense steric structure. Materials capable of vulcanizing rubber can be classified in three large categories: 1. Compounds which liberate sulfur during vulcanization, e.g., sulfur chloride and tetramethylthiuram disulfide. It is thought that nascent sulfur is particularly active, giving rise to the formation of crosslinks. 2. Compounds inducing vulcanization by means of radical reactions, such as peroxides. 3. Bifunctional compounds, among which phenol/formaldhyde derivatives seem to be the most interesting. Materials in the third group will be the object of this study.