Old thread I know, but anyway. Just wanted to clarify a coupl eo fthings:

Perspex=plexiglass=cast acrylic=PMMA=polymethylmethacrilate
PMMA is more scratch resistant than Lexan, but is very brittle. It also tends to break into large stabbing shards that tend to ruin ones day.

Lexan=HyZod=PC=polycarbonate
PC is very tough and impact resistance, but it scratched easily. You can actually fold a piece of PC over onto itself and the crease just turns white. It doesn't break. PC is used in F1 for the facemasks of the drivers.