Contact angles and the equilibrium spreading pressures of liquids on hydrophobic solids

摘要: Abstract When a spreading liquid or vapor can interact with substrate only by dispersion forces, as alkanes on any substrate, saturated hydrocarbon polymers, the equilibrium pressure is shown to be predicted exactly by: π e =2(γ d L γ S ) 1 2 −2γ where γLd force contribution surface tension γL of and γSd energy substrate. A new laboratory technique introduced for direct measurement πe hydrophobic solids, using difference in contact angles test solid air presence vapor. For cyclohexane polyethylene at 20°C found 7.19 dyn/cm; above equation predicts 7.15 dyn/cm. By this it proven unequivocably that high-energy liquids such methylene iodide water do not adsorb spread low-energy surfaces polytetrafluoroethylene.