Dynamic Surface Tension: Industrial Applications and Characterisation of Commercial Surfactants*

Abstract

Abstract In recent years dynamic surface tension has become increasingly used in industrial laboratories. For a wide range of applications it can be used to improve surfactant selection. Dynamic surface tension is a non-linear function of surface age and concentration. This must be taken into account when comparing surfactants. The concepts of effectiveness (magnitude of effect) and efficiency (concentration required for desired effect) are discussed. Efficiency parameters are more time-consuming to measure, but may give more relevant and reliable information. A ring test with an anionic surfactant using the maximum bubble pressure method showed good agreement between six laboratories. The results indicated that c20 (concentration for reducing surface tension by 20 mN m−1) at 0.1 s lifetime is a robust parameter for surfactant characterisation.