ESTIMATION OF THE SURFACE-TENSION COMPONENTS OF THIODIGLYCOL

The total surface tension of thiodiglycol was determined experimentall y, and its surface tension components were estimated: gamma(LW) = 42 /- 1 mJ m(-2), gamma(+) = 1.1 +/- 0.5 mJ m(-2), and gamma(-) = 25.0 +/ - 0.5 mJ m(-2). The Lifshitz-van der Waals component was estimated fro m experimental values of thiodiglycol/n-alkane interfacial tensions, m easured by the pendant drop method. The gamma(+) and gamma(-) were est imated using the additional information of the contact angle of thiodi glycol on a solid substrate with known surface energy components. Thre e polymeric substrates were used independently with this purpose: PS, SANE, and PMMA. The most consistent set of values was obtained using P MMA. The final establishment of the values for the surface tension com ponents of thiodiglycol involved a trial and error procedure where the parameters were slightly changed to reproduce the previously calculat ed surface energy components of the three polymer substrates. This stu dy reinforced the idea that the estimation of the surface free energy components of a liquid (or solid) is highly dependent on the calculati on method and on the systems used to perform the calculations.