Outgassing Testing: ASTM E595, TML/CVCM, and Vacuum Applications

What Is ASTM E595 Outgassing Testing?

ASTM E595 is a screening test method for determining Total Mass Loss (TML) and Collected Volatile Condensable Materials (CVCM) released by a material when exposed to a vacuum environment at elevated temperature — critical for qualifying polymers, adhesives, coatings, and composite matrix resins used in spacecraft, satellites, and other high-vacuum applications where contamination can degrade sensitive optics or electronics.

Testing for Outgassing by ASTM E 595 and IPC-TM-650 2.6.4

Outgassing materials are harmful for essential applications that demand a spotless vacuum environment. When a substance is heated and placed in a vacuum, it outgasses because some components are volatilized or released. A spotless vacuum environment is required for numerous applications, including processing lithography, sensitive analytical instruments, and spacecraft equipment.

The outgassing test must be used to screen the selection of materials, cleaning techniques, and handling practices in vacuum environments. When materials or components are exposed to a heated vacuum environment, the outgassing facility at InfinitaLab can calculate the total mass loss (TML) and collected volatile condensable material (CVCM) of those materials or components. In addition to surface contaminants like oils and release agents used during manufacturing, the mass loss may also be caused by outgassing of low molecular weight materials, including trapped process solutions, uncured materials (resin, adhesive, ink, paint, coating, etc.), uncured materials, and in some cases, plasticizers, flame retardants, and catalysts.

ASTM E 595 uses a vacuum chamber with 10-6 Torr pressures to heat the sample material. Material testing is carried out by putting known quantities of material in a 10x12x6 mm3 container boat placed inside a temperature-controlling hot copper bar. A venting port facing a collector on the container allows for measuring substances with lower volatilities. For the test, the copper bar, the materials being tested, and the collectors are kept at 125°C and 25°C, respectively.

Also Read – ASTM D6653: Altitude Testing for Packaging Systems — Complete Guide

Acceptance Criteria

Historically, TML of 1.00% and CVCM of 0.10% have been used as screening thresholds for rejecting spacecraft materials, though the final acceptance criteria are determined by the user based on the specific component and system requirements. Passing these thresholds does not guarantee the system or component will remain uncontaminated in service — subsequent functional and qualification testing is still recommended.

Known Limitation

The standard 24-hour test duration has been documented to underestimate maximum CVCM load by roughly a factor of two in some cases; modified protocols extending exposure to 48 hours have been used to compensate for this when a more conservative estimate is needed.

Industry Specifications Referencing ASTM E595

• NASA and ESA material qualification programs: primary users of E595 screening data
• Common materials tested: epoxies, adhesives, coatings, elastomers, composite matrix resins, thermal control materials

Conclusion

ASTM E595 is a screening tool, not a final qualification — TML and CVCM values below the historical thresholds indicate a material is a reasonable candidate for vacuum service, but component-level functional testing remains necessary before flight qualification.

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