Industrial processes frequently use surfactants to lower liquid surface tension and promote wetting. In many instances, it is incorrect to apply the equilibrium (static) surface tension to predict the behavior of these processes because they operate under time-dependent (dynamic) conditions. This paper describes the measurement of dynamic surface tension, that is, the surface tension under dynamic conditions where the limitation of surfactant diffusion to the growing interface results in tensions above the equilibrium surface tension. Experimental results, obtained using the maximum bubble pressure method, are presented for aqueous solutions of hydrocarbon and fluorocarbon surfactant systems and for dilute polymer solutions. In particular, the experiments have shown the combined effects of the rate of generation of a gas/liquid interface and the surfactant concentration on the surface tension. Noteworthy are results for fluorocarbon surfactant solutions which can exhibit dynamic surface tension behavior at exceedingly small rates of surface dilation. Synergistic effects of surfactant mixtures and the effect of temperature on dynamic surface tension are presented, as well as the effects of foaming and liquid viscosity on the measurement technique.
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