Capillary Flow Porometry (CFP) Instrument - Porometer

Gas-Liquid Porometry, also called Capillary Flow Porometry (CFP), measures pore size and pore size distribution of through pores in materials. The method is founded on the displacement of an inert and nontoxic wetting liquid embedded in a porous network by applying an inert pressurized gas. Thus, only through pores are measured.

Larger pores tend to get empty first and, as the applied pressure grows, likewise the smaller ones are emptied until all through pores are empty.

The toughest part for the gas to displace the liquid along the whole pore path is the most confined section, also referred to as pore throat. The diameter measured in CFP is the pore throat, irrespective of where precisely in the pore path it is. The technique relies upon the capillary rise developed by the surface tension between the gas and the liquid. Thus, a wetted pore immersed in a liquid pulls the liquid up the capillary until realizing equilibrium with the force of gravity.

Parameters Measured

In a standard CFP test, a flow of pressurized gas is applied to the porous sample impregnated with the wetting liquid, and the flow of gas through the sample, as the liquid is moved out of the porous network, is measured. The “wet curve” signifies the measured gas flow against the applied pressure. After the wet curve analysis, the gas flow against the applied pressure on the dry sample (“dry curve”) is also calculated. From the data gathered from the wet curve, the dry curve and the “half-dry curve” (dividing the flow values of the dry curve by 2) data about the porous network can be acquired.

Applications for Capillary Flow Porometry

Filtration Membranes - For the characterization of ceramic, polymeric, and hollow fiber micro and ultrafiltration media.

Non-Wovens - For melt blown and spun bound materials including moisture barriers, geotextiles for soil analysis, textiles, etc.

Paper - Paper products, cigarette, including printing paper, paper packaging, etc.

Porous Rock - Measurement of porous rock in petrophysical analysis, particularly beneficial for defining hydrocarbon potential of reservoir rocks

Sintered Metals, Ceramics, Additive Manufactured Parts - Application to establish porosity of functionally graded ceramics, ceramic supports, additive manufactured parts, porous metal frits, sintering effect in powder metallurgy.

Battery Separators - Separators are important components in liquid electrolyte batteries. A separator commonly consists of a polymeric membrane forming a microporous layer between the cathode and anode of a battery. Separators for Li-Ion batteries have a direct impact on the cell’s production, performance, and life, as well as battery safety and reliability.

Pore Characteristics Reported

Bubble point: Maximum pore diameter

Smallest pore size: Calculated at the pressure at which the dry curve meets the wet curve

Mean flow pore diameter: Pore size of which 50% of the total gas flow can be accounted (half the flow is via pores bigger than this diameter)

Gas permeability: In the same measurement, it is possible to acquire the gas flow rate. If the material area and thickness are identified, the gas permeability can also be reckoned.

Cumulative filter flow `{`SUM`}`: It reveals which flow percentage (at the Y-axis) has passed via pores with a size larger than the value at the matching point at the X-axis. It is also referred to as filter efficiency.

Differential filter flow `{`DIF`}`: It reveals the flow percentage (at the Y-axis), which has passed the pores with a matching size at the X-axis and the following size value at the same axis. According to ASTM, this graph reveals the so-called “pore size frequency”.

Pore size flow distribution `{`CDIF`}`: It reveals the flow distribution normalized per unit of change in size (flow variations are divided by size variations). Occasionally, it is also stated to as pore size distribution.

Capillary Flow Porometry (bubble point) is fixed by the following standards:

  • ASTM F316 – 03(2011)
  • ASTM E128 – 99(2011)
  • ASTM D6767
  • International Organization for Standardization (ISO) test standard 4003, and 7198

Capillary Flow Porometry (CFP) Instrument—Porometer

Measuring curves and resulting parameters in CFP (w= wet curve, d= dry curve, d/2= half-dry curve, FBP= largest pore, MFP= mean flow pore, SP= smallest pore)
Parameters Measured
POROLUX Porometers
POROLUX™ Software
POROLUX™ Pressure Step/Stability Series

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