Correct plastic?

Hello I need to make a a few pieces of armor and I know there are posts about this but I still find it unclear. I'm not vaccuforming but just using a heat gun to form it, I know what thickness I need but i'm not sure, i'm going to use USplastics what kind of styrene do I use? High impact styrene, ABS, foam-core or expanded high density PVC sheet? Ive seen people throw around all these different names and i'm not sure if it doesnt matter and I should just go with the cheapest one?

I've seen alot of people using ABS. Unfortunately it doesn't always look the best.

styrene or sintra (foam-core) is very easy form with a heat gun.

This is what you want

Expanded High Density Rigid PVC Sheet | U.S. Plastic Corp.

expanded high density PVC sheet = sintra

Yep. That's sintra. Sometimes you can luck out and go to a sign shop in your area and ask if they have any "scrap" pieces of sintra that they can give you or sell you cheap. Last piece I got was 4' x 3' for $5!