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INFORMATION REGARDING DENSITIES OF URETHANE FOAMS AND POLYESTER RESINS
MANUFACTURED BY CLASSIC SOLUTIONS INC.
High Density Urethane Foam .
This material was originally developed for the aerospace industry. It has no moisture
content and has a very low expansion/contraction factor. It has thousands of commercial
applications from home construction to nuclear submarines and of course signage.
Because of the aforementioned properties, not only is it very long
lasting, Whichever paint is used on the material it ages of very
gracefully, wood always has some moisture content in it and in the heat of the
summer, the moisture expands to form bubbles under the paint which then later become hard
when the paint is cold, and cracks.
This allows more moisture in and starts a
degenerative downward spiral of decay. HDU
has no moisture content therefore the cracking and peeling never start.
When manufacturers of sheet urethanes are producing their product their sole intention
is to get as even a density as is possible throughout the whole block. This is so
that when it is masked and sandblasted or carved an even finish results.
When we cast, our sole desire is to get an exact reproduction of whatever the mold in
question was made from. This is especially true where parts of the item being cast
differ greatly in depth. As you can imagine when the liquid is poured into the mold
it will run to the lowest areas. This can create a certain fluctuation in the
density. For the majority of our sign blanks this is not a problem but it is a fact that
everyone using our products should bear in mind.
Another factor to consider is that although the higher the density the
stronger the material, there is a point at which the material is so dense it becomes
brittle and although it takes quite a lot to break it, when it does break, it can shatter
(We have been working for some time now on a foam that is castable, and blastable but has
enough elastic memory to return to its original form after being impacted by something
like a golf ball (this is an ongoing project).
Polyester Resin
Typically has a density of approximately 60 lbs pcf. . Components can be added
to expand the volume of the resin, making it lighter, and sometimes weaker, but not
always. Other components can be added which will increase the density making it
much heavier and stronger. Again, there is a point where it becomes so dense, it
becomes brittle. Resins can also be rigid or flexible. We recommend therefore
that when inquiring about signs made from polyester that you explain what job the sign has
to do and where it is going.
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