Studies in the Vulcanization of Rubber. II—Vulcanization of Rubber with Nitro Compounds

The Kjeldahl method for nitrogen analysis can be adapted to the determination of combined nitrogen in rubber vulcanized with nitro compounds. The combination of nitro compounds with rubber has been followed in several cases. Strong evidence is given that the vulcanization is a chemical reaction. The density of rubber has been shown to change during vulcanization with dinitrobenzene. The change approximates the progress of the combination of the vulcanizing agent with rubber. The vulcanization of rubber with dinitrobenzene and trinitrobenzene is monomolecular. A theory of the mechanism of the vulcanization is advanced. The value of the stoichiometric method in estimating the molecular weight of rubber is discussed. Values of this constant are suggested by the data. Nitro compounds appear to be incapable of producing hard rubber. The amount of combined reagent is only a small fraction of that required for ebonite formation.