In article ,
"Peter Dohm" wrote:

"Orval Fairbairn" wrote in message
news
In article ,
"Peter Dohm" wrote:


I had simply presumed that all polycarbonate was nearly opaque to
UV,
that
acrylic was not, and that neither had much affect on IR; but there
now
appears to be a lot more to the story. I now suppose that you may
be
guessing exactly right that something is added to filter UV--and it
could
very well be throughout the material or as a coating. In addition,
polycarbonate was previously notorious for its poor abrasion
resistance,
and
its inability to be repolished; but the new formulations and/or
coatings
have drastically improved the durability.

I have a pair of glasses that darken (don't remember what they are
called)
that are safety glass rated, and have an anti scratch coating applied,
also.
They filter UV and have proven to be more scratch resistant by a
couple
levels of magnitude better than any others I have ever had.

Could it be that they finally figured out how to make a good scratch
resistant coating? I don't know the answer, but they are far better
than
the other coatings I have gotten in the past. Nice, too, that they
came
from Wally World, so the price was right.
--
Jim in NC


I don't know, but it's very possible.

Although mine don't change color, the scratch resistant coating has been
remarkably effective. There are no discernable scratches after a couple
of
years--despite treating them as though they were glass.

I hope that something as sturdy turns out to be available for canopies
and
windows.

Peter

Plexiglass II UVA has been around for decades! It filters out UV A, but
I don't know about UV B. It is the stuff from which aircraft canopies,
windows, windshields, etc. have been made for at least the past 45 years.

The only reference I could find was 280 to 400 nonometers, on the
RPlastics.com web page. According to the ThermoTecUSA.com web page, that
looks like the bottom third of UVB and all of UVA.

But, all of that brings up an ... umm ... interesting ... umm ...question
...
(Considering that I wasn't the only one on the NG who didn't know this)
Do you suppose ... presuming that your timeline is correct ... that OEMs for
both civil and military aicraft have been using the "right stuff" ... and
that Homebuilders may have been using whatever happened to be lying around
at the local plastic distributor?

Peter

YUP!