Surface characterization of a γ-radiation-crosslinked natural rubber latex by a phase transfer technique with cationic surfactants

A phase transfer technique was used to characterize the surface of a γ-radiation-vulcanized natural rubber latex (RVNRL). This technique involves titration of the negatively charged natural latex with cationic surfactants in the presence of an organic phase. The surface charge of the RVNRL was calculated from the amount of surfactant required to cause transfer of the rubber to the organic phase (critical transfer concentration). The optimum conditions of phase transfer were obtained when the organic solvent used was a 'good solvent' for natural rubber and its volume fraction was less than 0.5. The success of this technique was found to be dependent on the structures of the cationic surfactants that were used. These surfactants must contain either two long alkyl chains or one long alkyl chain and a benzyl group in their structures.