Nonoxidative crosslinking reactions in natural rubber. I. Determination of crosslinking groups

The presence of both epoxide and amine groups as integral constituents of the natural rubber macromolecule have been demonstrated, by application of an HBr double titration technique. The number of such groups is dependent on the clonal source of the rubber and is found to decrease on storage in step with an increase in the plasticity of the rubber. The groups are believed to be involved in nonoxidative crosslinking reactions which occur in rubber on storage. Possible crosslinking mechanisms are proposed.