In aerospace applications, material candidates are often screened for outgassing and offgassing properties. Outgassing is
the release of chemicals from non-metallic substances under vacuum conditions. Test method ASTM E595 is routinely
used to assess material outgassing characteristics. In this test, a material is held at 125˚C for 24 hours in vacuum, and
condensing volatiles are collected on a cooled plate. Test results include the sample’s percent total mass loss (TML%),
the percent collected volatile condensable materials (CVCM%), and percent water vapor regained (WVR%).
Offgassing refers to the release of chemicals from materials at ambient or higher pressure. Test method NHB 8060.1C
(Test 7) is commonly used to measure offgassing characteristics. In this test, the candidate material is held at 125°C and
ambient pressure for 72 hours. Gas sample analysis yields offgassed product identities and their concentration. For each
species, the ratio of the sample concentration to its SMAC (spacecraft maximum allowable concentration) is calculated.
The sum of these ratios is the T value of the material, or the Toxic Hazard Index.
Vectran®
fiber with either T97 or T150 finish provides excellent offgassing and outgassing characteristics (Table 7) in a
wide variety of aerospace applications.
Table 7: Offgassing and Outgassing Test Results for Vectran® HT Fiber| Vectran® Fiber with: | TML% | CVCM% | WVR% | T |
|---|
* Test results exceeded precision limits required to produce a statistically meaningful average. Individual samples
measurements: fiber without finish, 0.21 and 0.07%; fiber with T97 finish, 0.13 and 0.19%. ** The contribution of benzyl alcohol to this T-value is 2.214. The concentration in the sample was 0.31µg/g; no
measured SMAC value was available, therefore a conservatively low value of 0.14 µg/g was assumed. (KAI) |
| No finish | * | 0.00 | 0.00 | 2.226** |
| T97 finish | * | 0.00 | 0.00 | 0.009 |
| T150 finish | 0.30 | 0.00 | 0.00 | 0.015 |