Are theoretical surface chemistry measurements really practical

The principles and concepts of surface chemistry can be of enormous aid in the application of surfactant chemicals to practical cleaning and foaming problems. The use of surfactants for foam stability was seen to be dependent on rheological properties of the foam (bulk and surface viscosity) and to the energetics of the adsorbed surfactant monolayer (area/surfactant molecule, monolayer clasticity modulus, rate of monolayer spreading and rate of surfactant adsorption into the interface). From these principles, an equation predicting foam volume in the presence or absence of soil was derived and found to be in good agreement with experiment. In detergency, the performance was dictated by the thermodynamic work of adhesion between the soil and substrate. The adhesion was a function of surface properties (soil/water interfacial tension and soil/water/substrate). The role of agitation in detergency was shown to be that energy which was needed to overcome the adhesive bond between soil and substrate. The implicit form of the agitation term was discussed (dependent on substrate configuration, agitator system geometry and mechanics) but not explicitly deduced. The role of interfacial tension was discussed in relation to foam stability and detergency. In both applications, low interfacial tension is beneficial to performance. However, because other surface chemical effects play a role in performance in detergency and foam stability, it was noted that interfacial tension is not the sole correlating parameter with performance. The situations in which low interfacial tension is not sufficient to give improved detergency and foam stability performance were delineated. A possible new method of aiding in optimizing oil/surfactant performance also was discussed. Finally, the role of micelles in detergency was examined in light of very recent experimental work which suggests that micelles may be detrimental to detergency and foam stability performance. This study suggests that surfactants which form mesomorphic phases with soil give better performance. Micelles, instead of solubilizing soil in their hydrophobic cores, are said to be competing with the mesomorphic phase formation process, thereby hindering detergency performance. It is suggested by the sheer weight of new theoretical and innovative approaches to surface chemistry applied to detergency and foam stability performance that “theoretical surface chemistry measurements really (are) practical!”