Liquid Extrusion Porosimetry and the Measurement of Pore Size and Volume in Nonwovens

Nonwoven fabric is the name given to fabric-like materials that are made from long fibers (continuous long) and staple fiber (short) bonded together by mechanical treatment, heat, solvent or other chemical application. This method of production distinguishes non-woven materials from woven and knitted fabrics. Fibres may be oriented in one direction or deposited randomly to produce one or more fibre layers. The resulting products are flexible and porous. Felt is probably the most commonly known nonwoven material but the term also includes plastics like nonwoven polypropylene. A variety of manufacturing processes can be used, including spunlaid, staple nonwoven, flashspun and airlaid paper, to produce nonwovens.

Nonwovens have many applications in a wide variety of industries such as healthcare, biotechnology, paper, filtration as well as household uses. When in use they are subjected to compressive stress and the performance of nonwovens in such applications is largely determined by their pore structure. In order to assess this vital property it is important to characterise pore size, pore volume and pore volume distribution of nonwovens under compressive stress.nonwoven

The development of instruments that can measure such pore structure characteristics became a priority in the field and research developed the use liquid extrusion porosimetry to measure pore volume and pore diameter of a nonwoven under compressive stresses. The method uses a wetting agent, a liquid that can spontaneously flow into the pores of a sample. This is possible because the solid/wetting liquid interfacial free energy is less than the solid/gas interfacial free energy. Filling of the pores of the nonwoven sample with the wetting liquid therefore reduces the free energy of the system.

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Liquid-Liquid Porometry for Characterising Ultrafiltration Membrane Pores

Liquid-Liquid Porometry (LLP) is a valuable technique for measuring the pore structure characteristics of ultrafiltration membranes without damaging the membranes themselves. These membranes can act as barriers to a whole range of particles, both organic and inorganic, including bacteria, pollens, spores, pathogens and pesticides and even high molecular weight solutes, colloidal suspensions, and viruses.

Pore characteristics such as pore distribution, liquid permeability, pore throat diameter, bubble point pore diameter and mean flowpore diameter all offer valuable insights into pore function. However, capillary flowporometry a technique that can provide the required information about such characteristics uses high test pressures not suited for measuring ultrafiltration membranes. Liquid-Liquid Porometry (LLP) by comparison can measure the required pore structure characteristics without distorting the pore structure or damaging the membranes. In addition LLP is faster, uses less energy and lower pore sizes can be characterised.poro fror blog

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Mercury Porosimetry For Porous Structures – PASCALL Porosimeter

The mercury porosimetry technique is one of the most useful methods to investigate the porous structure of solid samples in a quantitative way. It provides reliable information about pore size/volume distribution, particle size distribution, bulk (envelope) density and specific surface for most porous solids.Porosimeter

Pressurization by Automatic Speed-up and Continuous Adjustment Logic, or, in short Pascal, is a special operating principle developed by Thermo Fisher Scientific and used in the new generation of automatic mercury porosimeters the Pascal Range, which reduces run times by up to 30%. Providing fast automated measurements with selectable intrusion/extrusion speed rates to minimise hysteresis effects, the PASCAL range provides maximum resolution in minimum time.  Continue reading Mercury Porosimetry For Porous Structures – PASCALL Porosimeter

Biotechnology and Healthcare

One industry sector that increasingly demands precise information on pore size and related characteristics is biotechnology and healthcare. Considering the number of porous materials now used in this branch of science, in such a variety of advanced applications, it is not surprising that there is much interest in the instruments described on this website. Continue reading Biotechnology and Healthcare

Automated Filter Cartridge Tester

Automated Filter Cartridge Tester - PMI

Filter cartridges are used in many industries, and in all cases there is a need to be aware of – and measure – their porous characteristics, properties and capabilities for R&D and quality control reasons. Pore size and material characterisation specialist PMI has an Automated Filter Cartridge Tester which assesses these products quickly, accurately and non-destructively. Continue reading Automated Filter Cartridge Tester

Batteries and Battery Separators

Batteries and separators

The porous nature of various elements in the structure of a battery has a crucial effect on its performance and is the subject of much material characterisation work using PMI instruments. Materials used to separate the cells in a battery are of particular concern, but so too are a number of other key components. Continue reading Batteries and Battery Separators

Sample Testing Services

Sample testing

Before you set out to buy an instrument for characterisation of any material, the first question you should ask is what will be the most appropriate method to obtain the information needed. As well as developing and manufacturing a range of high-quality analytical equipment, including porometers, permeameters and porosimeters, PMI can advise on what techniques to use – and can even do the analysis for you. Continue reading Sample Testing Services

Pore Size in Automotive Components


The automotive industry is just one of the many sectors that regularly make use of instruments for the measurement of pore size and other pore characteristics. Perhaps the most obvious components for which information on pore structure is needed – but not the only ones – are the various filters that play vital roles in the functioning of a vehicle. Continue reading Pore Size in Automotive Components

What Is a Porosimeter?

Liquid extrusion porosimeter from PMI

Liquid extrusion porosimeter

While exploring the topic of pore size and other characteristics of porous materials, the instruments we come across most regularly are the many and varied porometers and permeameters. Occasionally on this pore size website we have touched upon porosimeters, and for clarity I would like to return briefly to that subject today. Continue reading What Is a Porosimeter?

What Does a Permeameter Do?

PMI liquid permeameter

PMI liquid permeameter

When characterising the porous nature of a material we measure many aspects of pore size, but often we are also interested in the material’s permeability. This is, quite simply, a measurement of its ability to allow fluid to flow through it. We can determine permeability using a permeameter, of which many different varieties exist, and this is the topic I would like to dwell upon today. Continue reading What Does a Permeameter Do?