Abstract: The dilational viscoelasticity properties of the interface between fatty acid simulated oil and water and the effect of alkali and sodium dodecylsulfonate on the dilational properties of the interface of fatty acid simulated oil were studied.It is shown that their dilational moduluSIncreased with the increases of the dilational frequency and carbon chain length.When sodium dodecylsulfonate was added to the aqueous phase, the dilational modulus hardly changed; but the phase angle changed sharply when the work frequency was low.When the concentration of sodium hydroxide added to the water phase was low, whether sodium dodecylsulfonate existed or not, the dilational modulus did not change obviously.When the concentration of sodium hydroxide was high, the dilational modulus enhanced remarkably, and the slow relaxation process plays an important role, thus a special structure might be formed.

Key words: Acidic simulated oil, Dilational modulus, Phase angle, Dilational frequency