On May 1, 2005, at 7:01 PM, Roger K8RI on Tower wrote:
> Another vairable which can be critical is temperature. The best of
> resins
> soften with high temperature. That is why almost all fiberglass
> airplanes
> are painted white. I have forgotten the name used for the critical
> temperature when the epoxy softens, but it is relatively low. Some
> where on
> the order of 200 F. (give or take)
All this is true for homebuilt aircraft resins, which are necessarily
room-temperature curing resins. Because of the relatively low cure
temperatures, it is pretty easy to reach critical temperatures in the
post-cure phase. A dark surface in sunlight is sufficient.
Most composites used in high-performance commercial aircraft do not
cure at room temperatures. These typically are autoclaved at high
temperatures and pressures. This results in a stronger, lighter and
more stable part -- but the expense of the autoclave is high -- which
is why homebuilders do not use them.
However, this says nothing of the resin that Polyrod uses. I would
suspect they use a high-temperature epoxy. It would be interesting to
note the temperature ranges used in storage. Perhaps these coiled
rolls are just fine in Polyrods temperature-controlled warehouse, but
fracture when they sit outside in a field under a tarp covered with
snow in sub-zero temperatures....
> Vinyl Ester resin has a higher critical
> temperature at which it can be used and there are space age resins
> used in
> many of our fighterplanes that reach still higher temperatures.
This is because the resins require high temperatures (250-600
degrees) to cure.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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