Hydraulic permeability of open‐cell hydrophilic polyurethane foams

Abstract

SynopsisThe hydraulic permeabilities of open-cell hydrophilic polyurethane (Hypol) foams have been measured at steady state over a pressure gradient range of 10*-104 dyn/cm3. These permeabilities 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. Inertial losses, viscous losses, and energy losses associated with the pushing aside of loose foam struts were apparent a t high, low, and very low gradients, respectively. Over the gradient range investigated, compression of the foam was considered to be a minor factor in accounting for the decreased permeability a t higher gradients. The viscous loss term or Darcian permeability was correlated with cell size using the Carman-Kozeny 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.

Factors that enable the formation of porous strut morphology in “Swiss Cheese” viscoelastic polyurethane foam technology

“…These foams have exceptionally high air flow values of 6.5, 6.5, and 7.5 ft 3 /min for the 0, 5, and 10 pphp BO‐4000 formulations respectively. These facts are reminiscent of the findings by Sefton and Lusher with hydrophilic foams made from EO‐polyether based prepolymer, where “water flow” (hydraulic permeability) was found to correlate with inner pore size and strut diameter rather than average “cell size” (i.e., center‐to‐center distance of cells).…”

Porous media properties of reticulated shape memory polymer foams and mock embolic coils for aneurysm treatment

“…The porous media theory described in this study has been previously used to measure the geometrical parameters of polyurethane foams and fibrous porous media [ 39 - 42 ]. Additionally, blood flow through aneurysms treated with either embolic coils [ 23 - 26 ] or SMP foams [ 27 ] has been simulated utilizing porous media models.…”