Epoxidation of natural rubber in latex in the presence of a reducing agent

The in situ epoxidation of natural rubber latex was successfully performed in chain‐scissoring conditions. The chain‐scissoring process could be carried out simultaneously or successively to the epoxidation, to a determined extent. The rate and the degree of epoxidation depend on temperature, pH, and H2O2/isoprene units ratio. The chain‐scissoring reaction leads to a limited intrinsic viscosity range and, at pH 2–3, it was practically completed in 24–40 h. The gel content of epoxidized natural rubber (ENR) products are markedly reduced in the presence of reducing agent. Infrared spectra of ENR, thus prepared, are characterized by the presence of a typical weak band at 1550 cm−1, in addition to the other characteristic bands for normal ENR. At low pH and long‐lasting reaction, the epoxide ring undergoes a ring‐opening process, resulting in the formation of new OH, CO, ether groups, and slightly increased gel content. The Huggins constant, for a typical series of ENR obtained in redox conditions, was determined.