Lowoutgassing

Low-outgassing describes materials and processes that minimize the emission of vapors and gases under vacuum or elevated temperature. Outgassed vapors can condense on surfaces, contaminate optical components, degrade sensors, and increase chamber pressure, which is problematic in vacuum systems, semiconductor processing, and spacecraft instrumentation.

Standards and tests used to assess outgassing include NASA outgassing criteria and ASTM E595. This standard measures Total Mass Loss (TML) and Collected Volatile Condensable Material (CVCM) after bake-out in vacuum. Additional methods such as residual gas analysis help identify remaining species and partial pressures.

Outgassing arises from absorbed moisture, residual solvents, lubricants, adhesives, coatings, and bulk materials released when heated or placed under vacuum. The rate increases with temperature, humidity, and the presence of volatile additives, and it varies by material type and processing history.

Common low-outgassing materials include metals and ceramics, which typically exhibit minimal gas release. Some vacuum-grade polymers and composites are formulated for low outgassing, but many organic substances require bake-out, cleaning, and sometimes surface treatments or coatings to reduce emission.

Applications include vacuum chambers, semiconductor equipment, optical benches, space hardware, and scientific instruments where surface contamination or pressure rise would compromise performance.