How is the air permeability of different types of materials measured?

Permeability is an important physical property in materials that can affect many applications, such as construction, textiles and medical. Therefore, it is crucial to measure the permeability of different types of materials. This paper will describe the methods and techniques for measuring the breathability of different types of materials.

Main Body:

1. What is breathability?

Permeability is the ability of a material to allow air or water vapor to flow through its surface or inside. In architecture, breathability can help regulate indoor temperature and humidity; in textiles, breathability can affect comfort and warmth; in the medical field, breathability can help wound recovery and prevent infection.

2. Methods of measuring material breathability

(1) Osmosis method

The permeation method determines the breathability of a sample by applying air or water vapor to the sample and measuring the volume or mass flowing through the sample. Some common permeation methods for specific implementation include the mass method, pressure drop method and foam method.

(2) Hygroscopic method

The moisture absorption method is used to determine the permeability of a sample by placing it in an environment of constant humidity and measuring the change in mass of the sample. This method is usually used for materials that require consideration of water vapor transmission such as textiles.

(3) Flow method

The flow method is used to determine the permeability of a sample by measuring the air flow through the sample at a certain pressure. This method is usually used for materials that require consideration of air permeability, such as construction materials.

3. Measurement techniques

(1) Low differential pressure measuring instrument

A low differential pressure meter can measure the air permeability of a material by applying differential pressure. This technique can provide high accuracy and repeatability, but requires a longer time for testing.

(2) Laser Doppler velocimeter

Laser Doppler velocimetry can calculate the permeability of a material by measuring the velocity of air or water vapor over the material. This technique has the advantages of fast, non-contact and high accuracy, but requires specialized equipment and operators.

(3) Resistive sensors

Resistive sensors can calculate the permeability of a material by measuring the change in resistance of air or water vapor formed above it. This technique has the advantages of speed, accuracy and ease of operation, but requires calibration and maintenance.

Conclusion:

Permeability is an important physical property in materials and it can affect many applications. Measuring the permeability of different types of materials is critical and we can do this by methods such as permeation, hygroscopic and flow methods, and by using techniques such as low differential pressure meters, laser Doppler velocimeters and resistive sensors. In the future, with the development of new technologies and methods, we will be able to measure the permeability of different types of materials more accurately and provide better solutions for applications.