Mar, 29 2021

Low Outgassing Silicones with ASTM E595 Test Data



Low Outgassing Silicones with ASTM E595 Test Data

Specialty Silicone Products (SSP) makes low outgassing silicones and publishes the ASTM E595 test data that we receive from independent laboratories. All third-party test reports are available on SSP’s website so that you can view and download the results. Pacific Testing Laboratories of Valencia, California has tested numerous EMI/RFI silicones and Exova OCM has tested a 60-durometer sample of a USP Class VI silicone. Currently, several grades of SSP’s aerospace elastomers are being tested according to ASTM E595.  

What is ASTM E595?

ASTM E595 is a standard test method for total mass loss (TML) and collected volatile condensable materials (CVCM) from outgassing in a vacuum environment. Although the test itself does not specify maximum allowable limits, NASA has established requirements that are quoted and used. The most commonly quoted requirement is CVCM < 0.1% and TML < 1%. Because some water vapor (WVR) is regained after testing is complete, another (but less commonly quoted) requirement is CVCM < 0.1% and TML-WVR < 1%.

Why is Outgassing a Problem in Electronics, Optics, and Space?

When volatile compounds evaporate, they usually condense upon something else. This causes surface contamination and, depending on the contaminated material, problems such as corrosion or fogging. With microelectronics, volatiles that condense may cause devices to malfunction or fail. With optics, fogging occurs. With satellites, the vacuum pressure of outer space draws-out volatiles so that they escape more readily than at atmospheric pressure. Because it’s difficult if not impossible to repair or replace electronics and optics in outer space, it’s critical to use low-outgassing materials in applications such as satellites.

How Does SSP Make Low Off-Gassing Silicones?

SSP has access to silicone bases and polymers from a variety of producers. This allows us to formulate specialized materials that meet customer requirements not only for physical properties, but also for outgassing – or off-gassing, as it’s sometimes called. Today, SSP is working across different silicone chemistries to combine other desirable properties such as low temperature resistance or solvent and fuel resistance with low outgassing performance.

Low Outgassing EMI Silicones

SSP supplies low outgassing EMI silicones that are filled with metal or metal-coated particles and that use silicone or fluorosilicone as the base elastomer. These compounds can provide corrosion resistance, meet MIL-DTL-83528 requirements, or have UL 94-V0 flame resistance for offsets to discontinued GORE materials. Some of SSP’s EMI elastomers have low levels of outgassing with and without a pressure-sensitive adhesive (PSA). The following table provides product details.  

Product

Filler

Base

Notes 

SSP-2529

Nickel-Aluminum

Silicone

Corrosion resistant

SSP-2551

Nickel-Aluminum

Fluorosilicone

Corrosion resistant

Outgas tested with and without conductive PSA

SSP-2368-65

Silver-Aluminum

Silicone

Full compliance to MIL-DTL-83528 Type B

SSP-2486-70

Silver-Aluminum

Fluorosilicone

Full compliance to MIL-DTL-83528 Type D

SSP-550-45

Silver-Aluminum

Fluorosilicone

Low Durometer

Outgas tested with and without conductive PSA

SSP-550-70 Passivated

Silver-Aluminum

Fluorosilicone

Continuous roll stock grade vs. molded sheet

Outgas tested with and without conductive PSA

SSP-502-40-V0

Nickel-Graphite

Silicone

Flame retardant (UL 94-V0)

Offset to GORE GS2100

Outgas tested with and without conductive PSA

SSP-502-60-V0

Nickel-Graphite 

Silicone

Flame retardant (UL 94-V0)

Offset to GORE GS5200

Outgas tested with and without conductive PSA


Low Outgassing USP Class VI Silicones 

In addition to low outgassing silicones for EMI shielding, SSP makes elastomers without metal or metal-coated fillers. For example, SSP-2390 is a series of high-purity, platinum-catalyzed, translucent silicones that are USP Class VI and FDA CFR 177.2600* compliant for medical and healthcare applications. SSP sent a clear silicone slab of SSP-2390-60 to Exova Owa labs and received a report stating that the TML and CVCM levels are within the accepted range for outgassing.

Low Outgassing Aerospace Silicones and More Information

Currently, several of SSP’s specialty aerospace elastomers are being tested for low levels of outgassing according to the ASTM E595 standard test method. These SSP elastomers include MIL-DTL-25988 fluorosilicone and AA-59588, Class 1 low-temperature grades. For more information about our low outgassing elastomers, contact SSP on-line or email Dominic Testo.  

*See data sheet