Permeability testing is useful for evaluating airflow, gas, and/or liquid transmission/diffusion through materials. Permeability testing plays a significant role in industries including but not limited packaging, textiles, automotive, and construction. Here is a brief and simple guide through three of the most common permeability tests: Gurley Permeability Test, In Plane Gas Permeability, and Liquid Permeability Test.

What is the Gurley Permeability Test?

The Gurley Permeability test is a test to measure air permeability through a sheet of processed material (paper, fabric, plastic film, etc.). This testing method is named after Gurley Precision Instruments, the company that created the test.

How does the gurley permeability test function?

By using a machine called a Gurley Densometer.

The Gurley Densometer records the time it takes for a predetermined volume of air to pass through the material.

The results of test are expressed in Gurley seconds. The higher the number given, the less permeable the material (slow air passage). The lower the number given, the more permeable the material (quick air passage).

Why it's important:

Assists in the production of packaging materials that maintain the integrity of food or products.

Used for filters to measure airflow resistance.

To aid in quality assurance of paper and textile products.

What is In-Plane Gas Permeability?

in plane gas permeability is one way to determine the ability of gas to flow laterally through a material, as opposed to purely through a single axis, and is very useful in measuring materials like carbon fiber or composite fabrics that are used in aerospace or automotive applications.

How it works:

A volume of gas is forced through the material in one direction.

The test measures how quickly gas is flowing across the surface (or in-plane).

It helps engineers understand unique gas flow characteristics associated with complex materials.

Why it’s important:

In automotive or aerospace applications, gas flow can be critical for controlled processes.

In aids in the development of strong lightweight materials.

For safety in fuel and air systems.

What is the Liquid Permeability Test?

The liquid permeability test assesses the degree to which liquids diffuse through the material, and is typically applied to textiles, concrete, and membranes.

How does it work?:

A liquid (water or oil) is put on subject material

The velocity of the liquid that goes through and the amount of liquid that goes through, is measured

Ambient pressure, temperature, material thickness and other factors can impact the results

Why is this important?:

Used for testing waterproof fabrics (for example, raincoats)

Used for checking soil's or concrete's water movement

Oil and gas industry need to understand how fluids behave during transport, whether on pipeline or in filters

Conclusion

Permeability tests are "little" but powerful tests. They allow us to make better products for packaging, airplanes, etc. Whether it is air with the Gurley Permeability Test, gas with the In-Plane Gas Permeability Test, or liquid with the Liquid Permeability Test,