Plastic Signs is a common term, but there are many different types of plastic signs.

Plexiglass is a brand name for acrylic. This is what people normally mean when they ask for a plastic sign. A acrylic plastic sign is going to feel like a hard plastic with a little give to it, but not much. This is the most common plastic sign face in electrical box signs and channel lettering. For smaller plastic signs, acrylic has a very glossy or glassy finish to it, which gives them a very nice look.

Lexan is a brand name for polycarbonate. This is a more expensive plastic, but is used is larger plastic signs because it is easily produce in larger sizes.. It is much stronger that acrylic and has more flex to it. You can roll up lexan without it breaking. If a plastic sign face is more than 4' tall or 10' long, there is a good chance that it is lexan or another brand of polycarbonate plastic.