[TowerTalk] polyrod

[Bill Coleman]

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 at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901