Bubble pressure filter pore size analyzer basic principle - Database & Sql Blog Articles

Fundamental:
Taking a certain membrane material as an example, the membrane is sufficiently wetted with a liquid that can be infiltrated with it, and the infiltrating liquid is bound to the pores of the membrane due to the presence of surface tension; a gradually increasing gas pressure is applied to one side of the membrane, When the gas pressure reaches a pressure greater than the surface tension of the immersion liquid in a certain pore size, the immersion liquid in the pore size will be pushed out by the gas; since the pore diameter is smaller, the pressure generated by the surface tension is higher, so the immersion liquid is introduced therein. The higher the gas pressure to be applied is; also, it can be seen that the immersion liquid in the pore with the largest pore diameter will be pushed out first, allowing the gas to permeate, and then the pore diameter is increased from large to small as the pressure increases, and the pores are infiltrated. The liquid is pushed out in sequence to allow the gas to pass through until all the holes are opened to achieve the same transmittance as the dry film;



The pressure corresponding to the first opened hole is the bubble point pressure, and the aperture corresponding to the pressure is the maximum aperture; in this process, the pressure and flow rate are recorded in real time to obtain the pressure-flow curve; the pressure reaction aperture size information, flow rate Information on the number of pores in a certain pore size; then the pressure-flow curve of the dry film is tested, and the maximum pore size, average pore diameter, minimum pore size, pore size distribution, and transmittance of the membrane sample can be calculated according to the corresponding formula.
The relationship between pore size and pressure is like the Washburn formula:
D=4γCos θ/ p
In the formula, D = pore diameter γ = surface tension of liquid θ = contact angle and p = percentage of flow rate of pressure difference pore size distribution:
f(D) = - d[Fw/Fd)x100]/dD
In the formula, Fw is the wet sample flow rate, and Fd is the dry sample flow rate.