Impact of surfactant composition and surfactant structure on foam control performance

Foam control agents are commonly present in household laundry cleaning products to prevent excessive foam formation in horizontal axis washing machines. However, their effectiveness is highly dependent on the composition of the foaming medium and, in particular, the specific surfactants present. The reasons for this high surfactant selectivity are still poorly understood. This study examined the impact of both the composition of the surfactant solution and the chemical structure of the individual surfactants on the foam control effectiveness of a polydimethylsiloxane-based antifoam compound. Whilst high addition levels of the antifoam compound were required to control the foam of combinations of linear alkylbenzenesulphonate and alkyl sulphates, the inclusion of alcohol ethoxylates was shown to dramatically enhance the ability of the antifoam compound to control foam. Further, that the chemical composition of the alcohol ethoxylate and the structure of the hydrophobe chain played an important role. In contrast, the chemical composition and structure of the alkyl sulphate surfactants appeared to have relatively little impact.