LIGO Document E1800043-x0

Material Qualification RGA Test Results: EPO-TEK 302-3M adhesive

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E - Engineering documents
A measurement of the outgassing from EPO-TEK-302-3M adhesive in vacuum when properly prepared/mixed and cured at room temperature. The sample load consists of twelve (12) 25mm X 45mm mircroscope slides coated on one side with EPO-TEK-301-3M adhesive. They were put in VBO "D" Baked for 48 HRs @ 50C. For the RGA spectrum see ICS bake-8859:

The "flag" AMU hydrocarbon outgassing rate (~4.6e-9 tL/s) is ~10x higher than our typical maximum noise-floor limited apparent HC outgas rate. HOWEVER, bear in mind that the surface area of the epoxy samples are ~10^5 larger than the ~2 micron thick x 4 cm long edges on each of the 4 AMD devices per test mass. By scaling, the HC outgas rate for the 4 AMDs would be ~7e-14 tL/s, or in the acceptable range (see T040001).

The EPO-TEK 302-3M adhesive is currently planned to be used, with the addition of graphite powder, for the Acoustic Mode Damper (AMD) device. For the final AMD application, the total epoxy volume is only ~1 micron x 0.090 cm^2, or ~0.01 mg per AMD. Moreover the exposed surface area for outgassing is only ~1 micron x 1.2 cm = 0.0001 cm^2 per AMD. In the final AMD application we may have 4 AMDs per test mass.

An initial AMD trial is planned before observation run O3 where AMDs are bonded to the end test masses using EPO-TEK 302-3M instead of silicate bonding. This AMD-to-barrel bond will be thicker than the bond within the AMD assembly. If we assume the AMD-to-barrel bond is much thicker, say 10x, then the total bond surface area for this AMD trial will be ~10 x 4 x .0001 cm^2 = ~.004 cm^2 per ETM chamber.

FWIW we have approved EPO-TEK 353ND, another EPO-TEK "optical" epoxy (see E960050, E1300653 and E1300654) which also passes NASA low outgas testing. However EPO-TEK 353ND was cured at 80C for 30 minutes, whereas the epoxy for the AMD is proposed as a room temperature cure.

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