I prefer single or 2-flute cutters for plastics and other soft materials, because they clear chips better than 4-flute cutters, which I use for things like steel. If you're cutting thin sheets, I'd suggest a down-cut spiral, since it has less tendency to lift the material. For heat-sensitive plastics, consider an air chiller, like the Vortex: https://www.exair.com/products/cold-...t-systems.html