Low Outgassing Silicone for Aerospace and High-Vacuum Environments

When engineering components for aerospace, satellites, or high-vacuum manufacturing equipment (like semiconductor fabrication chambers), standard industrial materials fail in invisible but catastrophic ways. In these extreme environments, atmospheric pressure drops near zero, causing standard polymers to release trapped volatile compounds into the surrounding space.

This phenomenon is known as outgassing. If you are designing seals, potting compounds, or gaskets for these sectors, utilizing specifically formulated Low Outgassing Silicone is not just a preference; it is a strict mission-critical requirement. At Reemane, we engineer advanced silicone formulations designed to survive the rigors of high-vacuum applications. Here is what engineers need to know about outgassing and how to prevent it.

1. The Physics of Outgassing: Why It Happens

All elastomers, including standard silicone, contain microscopic amounts of volatile organic compounds (VOCs), unreacted polymer chains (low molecular weight siloxanes), and residual moisture.

Under normal atmospheric pressure, these compounds remain relatively stable inside the silicone matrix. However, when the component is subjected to a high-vacuum environment and extreme temperature fluctuations (such as the thermal cycling experienced in orbit), these trapped molecules vaporize and escape from the silicone.

2. The Threat of Condensation (Fogging)

Why is outgassing dangerous? The gas itself isn’t the primary issue; the problem is where that gas eventually condenses.

In the cold vacuum of space or inside a high-tech instrument, the outgassed siloxanes will search for the nearest cool surface and condense back into a solid or liquid film.

• Optical Degradation: If the gas condenses on a satellite camera lens, a laser targeting mirror, or a LiDAR sensor, it creates an oily, cloudy film (often called “fogging”). This permanently blinds the optical equipment.
• Electrical Failure: If the outgassed material settles on sensitive printed circuit boards (PCBs) or electrical contacts, it creates an insulating barrier that disrupts signals and causes system-wide failures.

3. ASTM E595: The Aerospace Standard

To ensure a material is safe for vacuum applications, it must pass rigorous testing, the most common being ASTM E595 (Standard Test Method for Total Mass Loss and Collected Volatile Condensable Materials from Outgassing in a Vacuum Environment).

During this test, the silicone is held at 125°C in a vacuum for 24 hours. To pass as an “aerospace-grade” low outgassing material, the silicone must meet two strict criteria:

• Total Mass Loss (TML): Must be less than 1.00%. This proves the material is not degrading.
• Collected Volatile Condensable Material (CVCM): Must be less than 0.10%. This ensures that the minimal gas that does escape will not condense onto nearby critical surfaces.

4. How We Engineer Low Outgassing Silicone

Achieving ASTM E595 compliance requires precise material science and controlled manufacturing environments. Reemane employs several strategies:

• Platinum-Cured Formulations: We strictly avoid peroxide-cured silicones, which leave behind acidic and volatile byproducts. Platinum-cured systems create an incredibly stable polymer matrix with near-zero residual outgassing.
• Advanced Post-Curing: The most critical step is the secondary vulcanization. We subject the silicone components to prolonged, high-temperature post-curing profiles in specialized industrial ovens. This “bakes out” any remaining low molecular weight siloxanes before the product ever reaches your assembly line.