how to tell plexi from other plastics

[FireMedic4Christ]

Is there a definitive test to determine which plastics may be plexi as opposed to another type? I've acquired a few signs that I was told was plexi but the previous owner was not sure.

Thanks,

Brian

 

[Possumpoint]

Plexiglas dissolves in acetone, polycarbonates soften only. This is the only test I know of. Others may know other ways.

 

[btboone]

Polycarbonates have rubbery shavings if you scrape it with a knife or file. Acrylics have whiter chips that are crinkly. The smell of each is unique when machining it. The acrylic seems to have a somewhat sweet smell and polycarbonates smell more rubbery. I'm sure there must be more scientific ways to tell.