Application of a trisiloxane surfactant for removal of oils from hydrophobic surfaces

Rates of advancing and receding menisci motion, nu, under applied pressure difference DeltaP in thin methylated quartz capillaries were investigated for trisiloxane solution-gas and trisiloxane solution-silicone oil systems. Dynamic values of the tension of wetting were calculated from the nu(DeltaP) dependence. Both dynamic surface and interfacial tensions and contact angles were assessed. Using solutions of the trisiloxane surfactant, M(D'E8OH)M, nearly complete displacement of silicone oils from hydrophobed capillaries becomes possible. Removal of silicone oil films of various viscosities from the methylated surface of thin (about 5 mum in radius) quartz capillaries using M(D'E8OH)M was investigated. In the case of spontaneous displacement, the oil film converts into a small oil column in front of the moving meniscus. The rate of oil film detachment follows diffusion kinetics as a result of penetration of surfactant molecules between the solid surface and the oil. Comparison of the volume of a smeared off and detached volume of the oil shows that silicone oils are displaced nearly completely. Using a video camera, transformation of a flat silicone oil film with base diameter 0.6 mm on a methylated glass surface into a floating spherical oil droplet was studied. Detachment of the droplet with diameter 0.19 mm occurs very rapidly during 14 s. Removal of an oil droplet sitting on an inclined methylated glass plate occurs as a result of oil emulsification in the course of interaction with a thick climbing trisiloxane film flowing around the droplet. The results obtained show that trisiloxane surfactants may be used not only as superspreaders but also as cleaning agents.