What is the Outgassing Phenomenon?

Did you know that many materials contain various types of gases , which can be released into the air under certain conditions?

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Outgassing is the name given to this phenomenon and today we talk about the importance of outgassing testing in some industrial sectors.

What is Outgassing?

Outgassing is the gradual release of gas previously trapped within a material due to factors such as humidity, heat, and low pressure.

Not all materials are subject to outgassing in the same way.

The materials most susceptible to outgassing are solvents, plasticizers, resins, adhesives, paints, and polymers; while metals are among the least susceptible.

The determining factor is the molecular structure of the material: the more compact and stable it is, the less it will release gas when subjected to extreme environmental conditions.

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Why Outgassing is Important.

Outgassing is of crucial importance in the industry aerospace for two reasons.

First, because low-pressure, extreme-temperature environments —like those of a spacecraft—are ideal conditions for triggering the phenomenon.

Second, because the particles released by outgassing can interfere with the electronic equipment necessary for the operation of the vehicle.

For this reason, it is necessary to subject many components in the aerospace industry to the Outgassing test.

What is the Outgassing Test for and How Does it Work?.

We've seen that all materials are subject to outgassing to some extent, but some types less than others. The outgassing test helps us further explore this understanding and discover which plastics, polymers, solvents, adhesives, and paints will necessarily be used in vehicle construction that will release the least gases.

The test consists of two phases.

First, the sample to be tested is placed in a thermo-vacuum chamber or in an environmental chamber, i.e. isolated environments in which the parameters of temperature, relative humidity and atmospheric pressure will then be altered.

The released gases will then be studied using infrared spectroscopy or mass spectroscopy to precisely determine the quantity and quality of the gases in question.

This way it will be possible to choose the materials that have the lowest gas release per surface.

The main international standard that outlines the procedures commonly used to perform the outgassing test is ASTME595.

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The FDM Environmental Chamber for Outgassing Testing

Outgassing test procedures involve very high temperatures and relative humidity, such as exposure to 125°C for 24 hours and 50% relative humidity for the same period.

For this reason, there is no better tool than the FDM environmental chamber, specialized in so-called extreme climate tests.

To test the pressure, , you need the thermo-vacuum chamber we talked about here.

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Reference Standards

• ASTM E595 — Total Mass Loss and Collected Volatile Condensable Materials Outgassing Test
• ECSS-Q-ST-70-02C — Thermal vacuum outgassing test for space materials
• NASA-STD-6016 — Standard Materials and Processes Requirements for Spacecraft
• SEMI F21 — Classification of Airborne Molecular Contaminants (AMC) for semiconductors
• ISO 14644-8 — Cleanchambers — Classification of AMC (airborne molecular contamination)

Authoritative Sources

• NASA Outgassing Database — Public database of 35,000+ tested ASTM E595 materials.
• ESA ESMAT outgassing database — European Space Agency reference for qualified materials.
• ASTM E595 standard.

Frequently Asked Questions about Outgassing

What is outgassing and why is it a problem?

Outgassingrelease of volatile molecules (plasticizers, solvent residues, absorbed moisture, additives) from polymer materials, adhesives, and paints when exposed to vacuum or high temperatures. In space environments, these molecules condense on cold optical surfaces, detectors, and solar panels, causing irreversible degradation. In semiconductor cleanchambers, they cause AMC contamination, resulting in chip defects. In medical devices, it can cause the release of non-biocompatible substances.

What are the ASTM E595 limits for spacecraft materials?

Two metrics measured after 24 hours at 125°C in vacuum: TML (Total Mass Loss) ≤ 1.0% initial mass; CVCM (Collected Volatile Condensable Materials) ≤ 0.1% on the cold trap plate at 25°C. Some stringent standards (telescopes, space optics) require CVCM ≤ 0.01%. A third parameter, WVR (Water Vapor Regained), measures post-test moisture absorption. NASA and ESA maintain public databases of qualified materials.

How do you reduce outgassing in production?

Common techniques: pre-assembly bakeout (24-48 hours at 80-125°C in a vacuum to eliminate volatiles); low-outgassing material selection (RTV-S691 silicone, Epo-Tek 301 series adhesives, Kapton polyimide); sealing with barrier coatings (parylene, PECVD SiO₂); N₂ purge during assembly to reduce moisture contamination. Pre-delivery thermal vacuum conditioning is used for critical optics and sensors .

What tests are complementary to E595?

For complete characterization: (1) GC-MS of traps to identify molecular species in CVCM; (2) VCM (Volatile Condensable Material) ECSS-Q-ST-70-29 with extended bake; (3) RGA (Residual Gas Analysis) during thermal vacuum for real-time monitoring; (4) ASTM E1559 for contamination rate on collector with QCM (quartz crystal microbalance). FDM creates thermal vacuum chambers for outgassing + thermal cycling tests.