Aerospace & Defense Technology - December 2023 - 23

Test & Measurement
rial selection. The ultra-low outgassing
materials were developed specifically
to meet the most stringent standards
for space applications, where even
low amounts of volatiles in traditional
space-grade materials might outgas
and cause potential problems. These
materials are expected to demonstrate
a TML of ≤ 0.1 percent and CVCM of ≤
0.01 percent by ASTM E595.
Figure 1 shows the percent of TML at
the end of testing as compared using
ASTM E595 versus ASTM E1559. Figure
2 lists the NuSil® space-grade silicones
included in the test, their cure chemistry
and the application for each tested
formulation.
The percentage of volatile condensable
materials (VCM) measured by
ASTM E1559 testing was just as important
as TML since these are the higher
molecular weight materials with lower
volatility, which can lead to mission
failure if found in sensitive areas. In
Figure 4, the results illustrate the substantial
difference in outgassing of volatiles
over time for low outgassing and
ultra-low outgassing silicones. While
all materials had CVCM of ≤ 0.04 percent
over 72 hours of testing, ultra-low
outgassing silicones showed CVCM
values of ≤ 0.001 percent, a full order
of magnitude less compared to the low
outgassing materials.
The testing demonstrates that ultralow
outgassing silicones are highly
suited for sensitive applications that
require minimum contamination to
ensure mission success.
Making the Right Material Choices
Selecting the right silicone manufacturer
with a proven track record of
extensive experience in the application
and customization of space-grade silicones
is as important as considering
the materials' function, purity and process
requirements when choosing a silicone
for space applications. The manufacturer
must provide advanced low
outgassing and ultra-low outgassing
materials that can withstand the rigorous
environmental demands of space.
In addition, the ideal silicone manufacturer
should have deep regulatory
experience, customization capabilities,
a comprehensive quality system and
Aerospace & Defense Technology, December 2023
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the ability to test space-grade silicones
on a lot-to-lot basis to ensure reliable,
compliant performance, ultimately
allowing for mission success anywhere
in the universe.
This article was written by Timothy
Steckler, Ph.D., Applications Technology
Manager, NuSil - a brand of Avantor.
For more information, visit www.
avantorsciences.com/nusil.
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