Low-rate dynamic contact angles on poly(methyl methacrylate n-butyl methacrylate) and the determination of solid surface tensions

Low-rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate/n-butyl methacrylate) P(MMA/nBMA) copolymer are measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It is found that 6 liquids yield non-constant contact angles, and/or dissolve the polymer on contact. From the experimental contact angles of the remaining 6 liquids, it is found that the liquid - vapour surface tension times the cosine of the contact angle changes smoothly with the liquid-vapour surface tension, Le., gamma(lv) cos theta depends only on gamma(lv) for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and non-inert (polar and non-polar) surfaces [34-42, 51-53]. The solid-vapour surface tension calculated from the equation-of-state approach for solid-liquid interfacial tensions [14] is found to be 34.4 mJ/m(2) with a 95% confidence limit of +/- 0.8 mJ/m(2), from the experimental contact angles of the 6 liquids.