Although capillary imbibition of solid foams is involved in many industrial applications, general theory for capillary imbibition has never been proved to apply for this specific class of porous materials. In order to compare accurately experiment and theory we produced solid foam samples with monodisperse pore size distributions and tunable pore volume fraction, and we measured their permeability (Darcy), their capillary pressure and their imbibition rate. Our findings revealed that the imbibition velocity is qualitatively compatible with the Washburn theory but it is one order of magnitude smaller than the predicted value. This deviation is attributed to the excess time spent by the liquid-gas interface through connections between pores, for which an empirical expression is provided as a function of pore size and solid volume fraction. Our results provide the first step to understand deeply the imbibition process in foams and to predict imbibition rates for various foamed materials.
Capillary imbibition in open-cell monodisperse foams, Olivier Pitois, Asmaa Kaddami, Vincent Langlois, Journal of Colloid and Interface Science 571 (2020) 166–173.