The components of surface tension of liquids and their usefulness in determinations of surface free energy of solids

Abstract

Measurements of the interfacial tension of glycerol-dodecane, formamide-dodecane, ethylene glycol-dodecane, and aqueous ethylene glycol solution-dodecane and the surface tension of ethylene glycol-water solutions were carried out. On this basis the surface tension components of these liquids were calculated and they were compared with values from the literature. It was found that they are close to J. Panzer's ( J. Colloid Interface Sci. 44, 142, 1973) results obtained by using solubility parameters. In order to verify whether the determined components of the surface tension of polar liquids are valid, measurements of equilibrium contact angles for these liquids were made on the surface of paraffin, polytetrafluoroethylene, polyethylene, polyethylene terephthalate, and polymethyl methacrylate. The measured values of contact angles were compared with those calculated, using the well-known components of the surface free energy. Good agreement was achieved among measured and calculated contact angle values and those obtained by other researchers. It was found that the calculated components of the surface tension of polar liquids worked well in the studied systems, and the geometric mean used for dispersion and nondispersion interfacial interactions gives good results despite existing intermolecular forces due to hydrogen bonding.