Limitation of the Young-Dupre equation in the analysis of adhesion forces involving surfactant solutions

The atomic Force microscope was used to measure adhesion forces between polyethylene particles, serving as model oil droplets. and mineral substrates (fluorite and quartz) in aqueous solutions of ethoxylated alcohols. Also. contact angles were measured in the kerosene ethoxylated alcohol solution-mineral systems. Correlations obtained between adhesion and surfactant concentration for the polyethylene -aqueous solution-quartz system differs significantly from those predicted by the Young-Dupre equation For the kerosene-aqueous solution-quartz system. Interactions, characteristic for such aqueous systems, which contribute to the pull-off forces measured by atomic force microscopy are nor included in the Young-Dupre equation, and are primarily responsible for the inconsistency in the adhesion versus surfactant concentration relationship obtained from contact angle measurements.