Material

Space Grade Silicone

Specialized elastomers that remain flexible at low temperatures and have low levels of outgassing

Stockwell Elastomerics offers space grade silicone and fabricates silicone gaskets for spacecraft and space vehicles. These specialized elastomers remain flexible at low temperatures and have low levels of outgassing. Stockwell Elastomerics uses various cutting methods to convert space grade solid silicone sheet and can also use compression molding to manufacture space grade gaskets for satellites, rockets, telescopes, and other applications. These materials are actively stocked to help meet customers’ development timelines. Additionally, these materials are available with robust certificates of analysis with data that is critical for space applications.

Low Temperature Flexibility and Silicone Gaskets

General purpose silicone can withstand temperatures as low as -73°C (-100°F), but that’s not enough for the near Earth region of space, where shaded objects may be subjected to temperatures below -100°C (-148°F). When cold causes an elastomer to become brittle, a gasket loses its ability to flex with changing thermal conditions. That’s why Stockwell Elastomerics makes silicone gaskets from the two specialized space grade materials described below that remain flexible in the low temperatures of space.

Space Grade Silicone Material with Extreme Low Temperature Flexibility

The first material, SSP4716, is a 65 durometer, phenyl-based silicone that remains flexible at extreme temperatures as low -116°C (-177°F). Compared to conventional dimethyl silicone, phenyl-based silicone offers enhanced thermal stability, improved radiation resistance, better oxidation and chemical resistance, and superior optical and refractive properties. SSP4716 has a tensile strength of 1350 psi and an elongation percentage of 600%. It is black in color as a standard but can be pigmented to meet customer specifications. It meets ASTM E595* low outgassing specifications.

Space Grade Silicone with Low Temperature Flexibility

The second group of materials, SSP4734-50LV and SSP4734-70LV, are methyl-based silicone materials that are available in either 50 or 70 Shore A. SSP4734-50LV is the 50 durometer version and SSP-4734-70LV is 70 durometer version.

SSP4734-50LV has a tensile strength of 975 psi and an elongation percentage of 400%
SSP4734-70LV has a tensile strength of 1080 psi and an elongation percentage of 300%

Both versions are available in black or gray color, but can be pigmented with other colors. They remain flexible in the low temperatures of space but do not have the extreme low temperature resistance of SSP4716. SSP4734-50LV and SSP4734-70LV also meet ASTM E595* low outgassing specifications.

Space Grade Silicone Materials Technical Specifications

Property	SSP4716	SSP4734-50LV	SSP4734-70LV
Durometer, Shore A	65	50	70
Tensile Strength, psi	1350	975	1080
Elongation, %	600%	400%	300%
Specific Gravity	1.18-1.24	1.29-1.25	1.29-1.25
Low Temperature Flexibility	-116°C (-177°F)	N/A	N/A
Chemistry	Phenyl-based	Methyl-based	Methyl-based
Color	Black	Black or Gray	Black or Gray

What is Silicone Outgassing?

In the near perfect vacuum of space, most materials release gases. Known as outgassing or offgassing, this phenomenon occurs because of the large difference in pressure between the interior of the material and outer space. With silicone gaskets for satellites and space vehicles, the release of volatile organic compounds (VOCs) and other residual chemicals may be problematic (depending on the application) because they can cloud camera optics or interfere with sensors and electronics.

SSP4716 and SSP4734-XXLV both meet the low outgassing requirements of ASTM E595*, a standard test that measures volatile content released in a vacuum environment of less than 5 x 10^-5 torr. ASTM E595* is the basis for NASA’s low outgassing test**, which focuses on Total Mass Loss (TML) and Collected Volatile Condensable Materials (CVCM). Historically, a TML of 1.00% and CVCM of 0.10% have been used as a screening level for the rejection of spacecraft materials.

Space Grade Silicone from Stockwell Elastomerics

Stockwell Elastomerics specializes in custom gasket manufacturing and custom formulated compounds using various silicone materials (including space grade silicones) and other elastomeric materials. For both SSP4716 and SSP4734-XXLV, Stockwell Elastomerics can provide corresponding test data and vendor certifications. These two space grade silicones materials are in stock and available in several standard thicknesses.