Chemical Inhibitors That Lower Viscosity and Increase Drainage

Chemical Inhibitors That Lower Viscosity and Increase Drainage 

Chemicals that reduce the bulk viscosity and increase drainage can cause a decrease in foam stability. The same applies to materials that reduce surface viscosity and elasticity (swamping the surface layer with excess compound of lower viscosity). 

It has been suggested that a spreading film of antifoam may simply displace the stabilising surfactant monolayer. In this case, as the oil lens spreads and expands on the surface, the tension will be gradually reduced to a lower uniform value. This will eliminate the stabilising effect of the interfacial tension gradients - that is, the elimination of surface elasticity. 

Reductions in surface viscosity and elasticity may be achieved by the inclusion of low- molecular-weight surfactants these will reduce the coherence of the layer, for example by the addition of small amounts of nonionic surfactants. These effects depend on the molecular stracture of the added surfactant. Other materials, which are not surface-active, can also destabilise the film by acting as cosolvents which reduce the surfactant concentration in the Hquid layer. Unfortunately, these non-surface-active materials (e.g., methanol or ethanol) need to be added in large quantities ( 10%). 

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