Liquid-Liquid Porometer

Liquid-liquid porometer - PMI

It’s always good news to me when I see a new porometer on the PMI website! This time it’s a liquid-liquid porometer specially designed for characterising pore size and structure in such materials as membranes, filter media, ceramics, paper and textiles.

What all of those materials have in common is that their pores are very small. This is no problem to PMI’s liquid-liquid porometer, which will accurately determine pore diameters and pore distributions as well as measuring flow rate even in materials with a low permeability. The new porometer comes in standard and nanoflow versions, to meet different needs.

The technique of porometry involves filling the pores of the material with wetting liquids. In fact two saturated liquids, immiscible with each other, are used. The first, which has a lower surface tension, fills the sample’s pores initially. A second liquid is added on top of it and pressure is applied so that the first liquid is displaced from the pores and the new liquid flows through them. An example of a suitable combination of liquids is silwick and alcohol.

The pore diameter can be calculated using a formula which takes into account the surface tension of the liquids and the differential pressure that needs to be applied to achieve displacement. The distribution of the pores, as well as the material’s permeability to liquid, can be computed with reference to the flow rates.

With the new liquid-liquid porometer it is possible to measure diameters as low as just several nanometres. Compared to a capillary flow porometer, this instrument needs much less pressure. It is also capable of measuring very low levels of liquid permeability.

As you might expect from a PMI instrument, the liquid-liquid porometer is easy to use. Its operation is fully automated, allowing accurate determinations of pore characteristics with the minimum of effort.

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