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epoxy weakens at moderately high temps?

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messydeer

Member
Joined
Mar 17, 2010
Messages
20
Location
Bellingham, WA
I've been looking for the best glue and moisture barrier for wood. Planning on building an Osprey. Below is from the Falco construction manual dated 2002.

'The principal limitation is that epoxies soften with heat, and the room temperature cure epoxies used on boats and homebuilt airplanes have poor performance at elevated temperature. Tests by Bellanca Aircraft showed that the two most popular epoxies used by homebuilders, Chem-Tech T-88 and FPL-16A, begin to soften at 125°F, have about 25% of their original strength at 150°F, and have a shear strength of only 40 psi at 175°F—about the same strength as library paste. (The epoxy industry is notorious for its lack of ethics in sales literature: Chem-Tech's literature for T-88 claims a shear strength of 1,000 psi at 180°F. Don't believe any claims unless you have run tests.) Tests by others have indicated that the West System epoxies have slightly better performance...And what does Gougeon Brothers say about our position on epoxy? The head of the testing department says that our position is exactly the same as theirs: that concerns about the temperature performance of room temperature cure epoxies are valid even though they are not aware of anyone having problems with white-painted epoxy-built wood aircraft. They know from tests that the temperature performance of West System is better than high viscosity flexible epoxies (such as T-88). They have not run enough tests at elevated temperatures to chart the performance of their epoxy system. They are hard at work developing an epoxy system with better temperature performance, but it is a difficult task. The reactive diluents which are needed to thin the epoxy for good penetration into the wood fibers lower the temperature performance, and the additives that raise the temperature performance have undesirable characteristics.'

This surprised me since I'd thought the most popular glue was T-88. Comments?

Dan
 
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