Why outgassing should be taken seriously

Gases can escape from both liquid and solid materials, which is known as outgassing and can lead to problems in the automotive industry, the electronics industry or the aerospace industry, among others. It can lead to a loss of performance and unreliability in certain components, which can have a negative impact on entire assemblies, devices and/or systems.

In order to keep outgassing in production as low as possible, certain manufacturers, such as Henkel, have special products in their range that are particularly low in outgassing and meet certain outgassing standards.

In the following article, we explain why outgassing should be taken seriously and which Loctite and Bergquist products from Henkel meet the NASA outgassing standard and the ASTM E595 standard.

How does outgassing occur?

Outgassing, i.e. the escape of gases from solid or liquid materials, can have various causes. For example, outgassing can occur due to pressure relief . Almost all materials outgas in a vacuum. This is because gas molecules have a tendency to move from an area of high pressure towards an area of low pressure, and in a vacuum there is an extremely low pressure level.

Outgassing can also occur due to an increase in temperature, as this leads to an increase in the kinetic energy of molecules, which become more volatile as a result, which can lead to a phase change to the gaseous state, both in liquid and solid materials.

Chemical, bacterial or radioactive conversion processes can also lead to outgassing.

There are four different mechanisms that can cause outgassing:

• Vaporization
• Diffusion
• Desorption
• Permeation

Evaporation occurs when a liquid or solid substance changes phase at the surface into a gaseous state.

During diffusion, gaseous molecules in a material move from the inside to the outside.

In the case of desorption, gas molecules are released that have accumulated on the surface, i.e. were adsorbed or absorbed.

Permeation is a form of outgassing in which gaseous molecules penetrate a material from the outside through the surface and then escape again at another point on the surface.

Problems due to outgassing

Outgassing causes problems in environments where the highest purity requirements apply, such as in semiconductor production. The outgassing substances can be water vapor, oil, grease or volatile organic compounds (VOCs). In particular, environments with vacuum and/or high temperatures pose special challenges for manufacturers of electronic devices, for example, which must also meet the highest cleanliness requirements in such environments.

However, outgassing can also lead to contamination of the materials used in other sectors, such as the automotive industry, and thus to performance losses and failures in electronic devices, such as sensors or control units.

The aerospace industry faces similar problems, as it cannot afford any loss of performance or even failures in electronic devices due to outgassing.

Measurement of outgassing

The US space agency NASA (National Aeronautics and Space Administration) has developed a technique for measuring outgassing due to the major challenges associated with it. ASTM E595 standard “Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment“). Basically, this is an outgassing test for materials in order to be able to decide whether these materials are suitable for use.

As the name of the ASTM E595 standard implies, the outgassing test of a specific material is used to test both the total mass loss and the amount of volatile, condensable substances collected during the test. The measurement result of the total mass loss is also referred to as the TML value, whereby TML is the abbreviation of the English term “Total Mass Loss”. Specifically, the TML value represents the percentage of the original mass loss of the tested material caused by the outgassing test, whereby the material is exposed to high temperatures and a vacuum during the test.

There is also a value for the measurement result of the collected volatile , condensable substances, namely the CVCM value, where CVCM is the abbreviation for “Collected Volatile Condensable Materials”. The CVCM value expresses the percentage of volatile substances that condense during outgassing, i.e. that change from the gaseous state to the condensed state during the outgassing test. To be acceptable as a material according to NASA or the ASTM E595 standard, the TML value determined in the outgassing test must be equal to or less than 1 percent, and the CVCM value must not exceed 0.1 percent.

Henkel products according to NASA outgassing standards

NASA and the ASTM E595 standard therefore place high demands on the outgassing of materials. The following Henkel Adhesives products from the Henkel brands Loctite and Bergquist meet the outgassing standards of NASA and theASTM E595 standard:

Electrically conductive pastes

Source: Henkel AG & Co. KGaA

Encapsulant

Source: Henkel AG & Co. KGaA

Conformal Coatings

Source: Henkel AG & Co. KGaA

Electrically conductive adhesive film

Source: Henkel AG & Co. KGaA

Electrically insulated adhesive film

Source: Henkel AG & Co. KGaA

Underfillings

Source: Henkel AG & Co. KGaA

Electrically non-conductive pastes

Source: Henkel AG & Co. KGaA

Thermal interface materials – gap fillers

Source: Henkel AG & Co. KGaA

Thermal interface materials – Gap Pad

Source: Henkel AG & Co. KGaA

Thermal interface materials – Sil Pad

Source: Henkel AG & Co. KGaA

Here you will find a wide range of Henkel products in the abovo online store.

Advice on Henkel products with low outgassing

For more than 15 years, the Swiss specialist wholesaler abovo has been an authorized distributor for the Henkel Adhesive Technologies division Henkel Elektronik (Henkel Electronic Material) and, since 2022, also for the Henkel Industrial division.

We will be happy to advise you if you have any questions about Henkel Adhesives products of the Henkel brands Loctite and Bergquist as well as with regard to the outgassing standards of NASA or theASTM E595 standard.

Contact our Henkel experts simply and without obligation by phone or e-mail:

• Telephone number: +41 32 552 44 44
• E-mail: info@abovo.ch