SURFACE CHARACTERIZATION OF A GAMMA-RADIATION-CROSS-LINKED NATURAL-RUBBER LATEX BY A PHASE-TRANSFER TECHNIQUE WITH CATIONIC SURFACTANTS

A phase transfer technique was used to characterize the surface of a g amma-radiation-vulcanized natural rubber latex (RVNRL). This technique involves titration of the negatively charged natural latex with catio nic surfactants in the presence of an organic phase. The surface charg e of the RVNRL was calculated from the amount of surfactant required t o cause transfer of the rubber to the organic phase (critical transfer concentration). The optimum conditions of phase transfer were obtaine d when the organic solvent used was a 'good solvent' for natural rubbe r and its volume fraction was less than 0.5. The success of this techn ique was found to be dependent on the structures of the cationic surfa ctants that were used. These surfactants must contain either two long alkyl chains or one long alkyl chain and a benzyl group in their struc tures.