Porometry Made Simple

PMI porometer

Among the many pore characterisation products currently described on the PMI website is a ‘Simple Porometer’. It reminds me that now might be a good time to go back to basic principles and tell new visitors to Pore Size about what a porometer is and why it is so useful.

What a porometer does is measure and assess various aspects of the porous nature of a material under study. This includes such useful pore size measures as the diameter of a through pore (a pore that connects with others) at its most constricted part (the pore throat diameter). Other measurements include the largest pore diameter and the mean diameter, the distribution of the pores and the gas permeability of the material.

How it works is by filling the pores in the sample, spontaneously, with a wetting liquid and then applying a non-reacting gas to one side of the material, under slowly increasing pressure, until the liquid is removed and the gas is able to flow through the pores.

The pressure required for this to occur, together with the flow rates of gas through the wet and dry sample, is used to calculate various characteristics of the pore structure.

This is the simple version but, as you can imagine, there are advances in design which make some porometers more accurate and reliable than others. There are also specialised adaptations for particular tasks – hence the great variety of products available from a manufacturer such as PMI.

The capabilities of these instruments include determination of pore structure in both the thickness (z) and the in-plane (x and y) directions. Porometers can be designed to accommodate samples of many sizes and shapes, and to allow testing of materials without removing samples from the product. The effects of various factors on pore structure can be studied, to see how the material will react to the conditions it may face during use.

There are many optional extra features that can be added to a basic porometer, to increase its efficiency and adapt it to particular applications, of which you will find details via the PMI website www.pmiapp.com.

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