Abstract: The defoaming and foam inhibiting performance of three kinds of defoamer (silicone oil,poly ether ester,and poly ether modified poly siloxane) were assessed according to defoaming test standard ASTM E2407;and the influence with respect to dilational modulus,dilational elasticity and dilational viscosity of the simulated foaming system by different defoamers were tested with LB balance.Results showed that the defoamer molecules are adsorbed on the gas/liquid interfacial film,which weaken the elasticity and the strength of the interfacial film,as well as attenuate the thickness of the film;thus result in shortening of foam existing time and finally foam rupture.Under the existing of defoamer molecules,stable foam layer cannot be formed within a certain time period due to the strength weakening of the interfacial film and thus result in the foam inhibiting effect.Within a certain mass fraction range,the higher the mass fraction of the same defoamer,the lower the interfacial film dilational modulus and dilational elasticity,and the better of the performance of defoaming and foam inhibiting.When the mass fraction exceeds a certain value,the interfacial dilational modulus and dilational elasticity essentially keep no change,and the performance of defoaming and foam inhibiting shows no more enhancing.For different types of defoamer,the higher amplitude of reduction capacity of interfacial film dilational modulus and dilational elasticity of the defoamer,the better performance of defoaming and foam inhibiting.Therefore,dilational modulus and dilational elasticity are correlated to defoaming and foam inhibiting performance of the defoamer.

Key words: deformer, defoaming performance, foam inhibiting performance, gas/liquid interfacial film, dilational modulus, dilational elasticity, dilational viscosity