In "This Old Boat," Tom Casey says that the acrylics -- Plexiglas,
Lucite, Acrylite -- tend to develop a spider web of internal cracks
as it endures the stresses of age and movement. And that these
internal cracks weaken and cloud the plastic.
He raves about Lexan as a hatch material, calling it "incredibly
tough and stable."
Of course "tough" is one of those words that are not used with great
precision.
Materials people and books tend to use "tough" to describe a
material's resistance to crack propagation (i.e., a scratch turning
into a fracture; thus, glass is not tough, but wood is). They tend to
use "hard" to describe a material's resistance to being scratched in
the first place (thus glass is hard, but wood is not).
Sounds like you folks are looking for hardness. There are some pretty
standard measures of hardness, so I would think it would be easy to
compare materials.
I, too would like to know more about these materials, especially
since I'm getting ready to do a (non-Potter) project that will
consume maybe 80 square feet of this rather pricey stuff.
I'd be particularly interested if anyone knows of mail-order sources
for Lexan and/or the acrylics. Here on Maui, I can expect to be price
gouged for something like this.
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Rich Duffy
P-14 #362, "Manele"
Kula, Hawaii