Experimental study on the effect of formulation and hydrodynamic variables on non-aqueous foams stability

This study investigated the factors affecting the foamability and stability of non-aqueous foams. The researchers systematically varied the formulation (surfactant and alcohol type and concentration) and flow parameters (viscosity and gas flow rate). A custom setup with an 80 cm temperature-controlled glass column was used for foam generation. Among the tested non-ionic surfactants type sorbitan esters, the Span 80 (liquid W/O emulsifier and O/W emulsion stabilizer) produced the most voluminous foams. Interestingly, increasing surfactant concentration improved foamability but decreased foam stability. Similar trends were observed with the oil fraction and temperature (which affects viscosity). Higher viscosity led to more stable but less foamy structures. The study also explored the effect of different alcohols (ethanol to n-decanol) at varying flow rates. While all alcohols generated some foam at lower flow rates (200 mL/min N₂), the effect diminished at higher flow rates. Additionally, foam stability and volume decreased with longer alcohol chains. These findings provide valuable insights into the interplay between formulation, flow conditions, and the resulting stability of non-aqueous foams.