Material Danger! Cause/Consequence
PVC (Poly Vinyl Chloride)/vinyl/pleather/artificial leather Emits Chlorine gas when cut! Don't ever cut this material as it will ruin the optics, cause the metal of the machine to corrode, and ruin the motion control system... And Chlorine Gas is deadly!
Thick ( >1mm ) Polycarbonate/Lexan Cuts very poorly, discolors, catches fire Polycarbonate is often found as flat, sheet material. Polycarbonate strongly absorbs infrared radiation! This is the frequency of light the laser cutter uses to cut materials, so it is very ineffective at cutting polycarbonate. Polycarbonate is a poor choice for laser cutting.
ABS Emits cyanide gas and tends to melt ABS does not cut well in a laser cutter. It tends to melt rather than vaporize, and has a greater chance of catching on fire and leaving behind melted gooey deposits on the machine. It also does not engrave well (again, tends to melt).
HDPE/milk bottle plastic Catches fire and melts It melts. It gets gooey. Don't use it.
PolyStyrene Foam Catches fire It catches fire, it melts, and only thin pieces cut. This is the #1 material that causes laser fires!!!
PolyPropylene Foam Catches fire Like PolyStyrene, it melts, catches fire, and the melted drops continue to burn and turn into rock-hard drips and pebbles.
Fiberglass Emits fumes It's a mix of two materials that cant' be cut. Glass (etch, no cut) and epoxy resin (fumes)
Coated Carbon Fiber Emits noxious fumes A mix of two materials. Thin carbon fiber mat can be cut, with some fraying - but not when coated.

Based on: https://cpl.org/wp-content/uploads/NEVER-CUT-THESE-MATERIALS.pdf