Surface tension component method liquid-solid interface

The harmonic mean equation is generally considered to be applicable to low surface tension materials such as organic polymers and liquids. If y and y are known for two liquids, and the contact angles of those liquids on the solid of interest are measured, equation 36 produces two simultaneous equations that can be solved to find the surface tension and polarity of a solid polymer surface. Numerous assumptions have been made in developing the theory of fi actional polarity. For example, it ignores the possibility of induced polarity at the interface between polar and nonpolar materials (82). These assumptions limit the application of equation 36 to systems where at least one and preferably both of the components are relatively nonpolar. The theory breaks down when interfacial interactions lead to molecular rearrangements at the interface between solid and liquid. In addition, it was foimd that pairs of liquids with similar dispersive and polar components of surface tension gave umeasonable results for the substrate surface tension calculated by the harmonic mean method (83). 

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