Thermodynamic characterization of a non-commercial emulsifying agent for asphalt emulsion.

The objective of the present work was to characterize a non-commercial emulsifying agent: dodecylpyridinium thiocyanate (C12PCNS). This study was carried out by conductimetry technique in the temperature range 25-50 °C. Assuming the system conforms to the pseudo-phase separation model, change of standard Gibbs free energy, ΔGm0, enthalpy, ΔHm0, and entropy of micellization, ΔSm0, were estimated. Values for critical micelle concentration (cmc) and the ionization degree, β, were determined directly from the experimental data. The results show that the influence of the counter ion is very relevant, because the cmc for this compound is appreciably greater than the cmc of other pyridinium homologs of the same chain length. Finally, the compensation rule for this system has been found and the compensation temperature and the intercept ΔH*-it is an indication of the stability of the micelle-were estimated.