UPPER LIMITS FOR THE CONTACT ANGLES OF LIQUIDS ON SOLIDS
NAVAL RESEARCH LAB WASHINGTON DC
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Earlier systematic studies of the angle of contact theta exhibited by drops of liquid on plane solid surfaces of low surface energy have made data available on equilibrium contact angles. These data were obtained under well- controlled and comparable experimental conditions for many liquids on over 100 different solid surfaces. Examination of the data for eight, selected, pure liquids water, formamide, methylene iodide, hexachloropropylene, t- butylnaphthalene, dicyclohexyl, n-hexadecane, and n-decane reveals a wide variation in the wetting behavior of any single liquid toward different solid surfaces. For each liquid, however, graphical plots of cosine theta versus the difference in the surface tension of the pure liquid and the critical surface tension of spreading of the solid are found to group available data into a zone bounded by a straight line passing through the origin. From the parameters defining this straight line, estimates can be made of the limiting contact angles for each liquid.
- Physical Chemistry