The physical and chemical properties of the ideal defoamer must meet the requirements of the system.Generally speaking, the following requirements must be considered when selecting defoaming agents :

    (1) Strong defoaming ability, using a very small amount of foam can effectively eliminate;

    (2) it has lower surface tension than the defoaming system;

    (3) the addition of defoaming agent does not affect the basic properties of the defoaming system;

    (4) insoluble in defoaming system, is not easy to be dissolved by the surfactant system;

    (5) Good surface tension balance;

    (6) Does not react with the defoaming medium, nor will it be decomposed and degraded, with good chemical stability;

    (7) It has good diffusivity and permeability, positive diffusion coefficient in the foam medium, and fast spreading ability on the foam surface;

    (8) Good heat resistance, will not lose effectiveness at high temperature;

    (9) Good gas solubility and permeability;

    (10) in the defoaming system has high physiological activity and safety, defoaming agent itself is non-toxic or low toxic substances;

    (11) have low chemical oxygen demand (COD), biochemical oxygen demand (BOD) and total oxygen demand (TOD);

    (12) It has good storage stability;

    (13) with a long time defoaming effect, some defoaming agent can quickly defoaming, but a long time that failure;

    (14) Low cost;

    (15) do not increase the surface viscosity of surfactant aqueous solution.