Surfactants are important class of material used in latexes to impart stability at the
solid/liquid interface. Ionic surfactants and nonionic surfactants are known to provide electrostatic
and steric stabilisation. In this study, two surfactants having chain length of twelve
hydrocarbons were added to the natural rubber latex (NRL) respectively to determine its zeta
potential values, adsorption isotherm and rheological properties. Previous study has shown
that optimum stability was observed when the alkyl chain of surfactant contains twelve carbon
atoms. The zeta potential magnitude of NRL in the presence of sodium dodecyl sulphate
increased as the surfactant concentration increases, while polyoxyethylene dodecyl ether did
not show a significant change in zeta potential. The isotherms were of Langmuir Type 1, the
amount of surfactant adsorbed per unit area at the plateau region was 6.0 × 10−6 mol m−2
for sodium dodecyl sulphate and 2.1 × 10−6 mol m−2
for polyoxyethylene dodecyl ether.
The elastic modulus and relative viscosity of the NRL suspensions increased significantly
in the presence of sodium dodecyl sulphate and also with polyoxyethylene dodecyl ether as
compared to the NRL system due to stronger colloidal forces. The maximum packing volume
fractions of the NRL stabilised with sodium dodecyl sulphate and polyoxyethylene dodecyl
ether were found to be lower than NRL itself.