Firefighting foam stability: the effect of the drag reducer poly(ethylene) oxide

The presence in fluids of very small amounts of high molecular weight polymers produces high levels of drag reduction in the fluid flow. This phenomenon, often termed the Toms Effect, can be used in firefighting, mainly due to the reduction in the energy necessary to pump water. The use of one of the most efficient drag reducing agents - poly(ethylene oxide) (PEO) - dissolved in the firefighting foam concentrate can significantly increase foam flow. This paper describes studies of the stability of foam generated from a commercial firefighting foam concentrate with added PEO. These studies were based on the lifetime of foams generated with and without small concentrations of PEO. It was observed that the presence of PEO increases the lifetime of the foam. This result is attributed to changes in the drainage rate due to the adsorption of the polymer at the liquid -/air foam interface. The adsorption is probably a consequence of the polar interaction of the ether group of PEO and the polar head of the surfactant.