Hydraulic permeability of open‐cell hydrophilic polyurethane foams

Abstract

AbstractThe hydraulic permeabilities of open‐cell hydrophilic polyurethane (Hypol) foams have been measured at steady state over a preassure gradient range of 102–104dyn/cm3. These permeabilites were sensitive to the relative amounts of prepolymer, water, and surfactant, and to the mode of preparation, Furthermore, the noted sample‐to‐sample variations suggested that mixing effects were also significant. Intertial losses, and energy losses associated with the pushing aside of loose foam struts were apparent at high, low, and very low gradients, respectively. Over the gradient range investigated, compression of the foam was considered to be a monor factor in accounting for the decreased permeability at higher gradients. The viscous loss term or Darcian permeability was correlated with cell size using the Carman–Kozeney equation indicating that the major determinant of hydraulic permeability was pore size rather than porosity. The fiber drag model of flow through porous media was also used to account for the permeability in terms of strut diameter rather than cell size.