The rheological properties of pharmaceutical foam: Implications for use

We have evaluated various aerosol foam types having different compositions and related physico-chemical properties. The foams assessed were hydroethanolic, emulsion, and aqueous based. Composition, appearance, loss on drying, and rheological properties were analysed to characterise the macrostructure of the different aerosol foams. To confirm the validity of the vane rheological technique used, and facilitate intuitive understanding of the data, similar data were collected for a commercial shaving foam. Of the physico-chemical parameters that were evaluated, rheological properties were distinct among hydroethanolic, emulsion, and aqueous aerosol foam types. The results indicate that beyond composition differences, physico-chemical differences do exist between these aerosol foam types. The viscoelastic flow properties provided an insight of the macrostructure of materials that have been foamed.