Stabilising ability and hydrophile-lipophile balance of surfactants

Stabilising Ability and Hydrophile-Lipophile Balance of Surfactants 

The correlation between the volume or stability of the foam and the hydrophile-lipophile balance (HLB) of surfactants or their mixtures is used to generalise the experimental results derived about the stabilising ability of complex foaming compositions or homologues surfactant series. HLB is an important surfactant parameter, characterising the relative 

A closer relationship between foam stability and HLB has been reported for two- or three-phase systems surfactant solution-oil or oil-surfactant phase-water [60,109-111]. The effect of various parameters changing HLB on the stability of foams and emulsions has been studied in [111]. These were the concentration of amyl alcohol and sodium chloride, the number of the ethylene oxide groups in the molecule of the oxyethylated octylphenol. As a general parameter of HLB the authors used the surfactant affinity difference concept (SAD) which is an empirical generalised formulation. It measures the deviation from the optimum formulation for three phase behaviour. For anionic surfactants 

In these relations S is salinity of the aqueous phase expressed in wt.% NaCl /(A) and 0(A) are function of the alcohol type and concentration they decrease (starting from zero) upon increasing the alcohol content in the system n0E is the average number of ethylene oxide groups per non-ionic SAS molecule k, a, b, c and cr are constants nc is the number of carbon atoms in the alkane forming the oil phase. 

Raising both the electrolyte and alcohol concentration and reducing nno leads to increasing SAD. If an immiscible micellar phase containing surfactant, oil and water is formed, SAD 0, in the more hydrophile range SAD 0 and in the more hydrophobe range, SAD 0. 

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