Low-rate dynamic contact angles on poly(methyl methacrylate/ethyl methacrylate, 30/70) and the determination of solid surface tensions

Low-rate dynamic contact angles of 12 liquids on a poly(methyl methacrylate /ethyl methacrylate, 30/70) P(MMA/EMA, 30/70) copolymer were measured by an automated axisymmetric drop shape analysis-profile (ADSA-P). It was found that five liquids yield nonconstant contact angles, and/or dissolve the pol ymer on contact. From the experimental contact angles of the remaining seve n liquids, it is found that the liquid-vapor surface tension times cosine o f the contact angle changes smoothly with the liquid-vapor surface tension (i.e., gamma(lv) cos theta depends only on gamma(lv) for a given solid surf ace or solid surface tension). This contact angle pattern is in harmony wit h those from other methacrylate polymer surfaces previously studied.(45,50) The solid-vapor surface tension calculated from the equation-of-state appr oach for solid-liquid interfacial tensions(14) is found to be 35.1 mJ/m(2), with a 95% confidence limit of +/- 0.3 mJ/m(2), from the experimental cont act angles of the seven liquids. (C) 1999 John Wiley & Sons, Inc.