What kind of plastic can stop a bullet?

Industrialized plexi glass. I see these at the bank.

I am a technician in a plastics factory and I work with many types of plastics, and Polycarb happens to be one of them...

The polycarb we use is made by the General Electric Co. called Lexan... the mixture is 104r and it is NOT bullet proof in its Purge form but is considered a "Ballistics polymer" I've tried out its "Bullet-proof-ness" the piece of purge I used was approx. 3 inches thick and about 2 feet in diameter... weight was approx. 30 Lbs.... We fired 3 rounds into it from 3 different calibers: 300 Weatherby Mag, .223 Remington, .22LR The only round that didn't pass through was the .22LR, Bullet proof glass wasn't designed for high-powered, high-velocity rifle projectiles, is was more based on protection from incoming pistol rounds.... Bullet proof glass is manufactured with just about the same design as a car wind shield.... "layer of tempered glass, layer of ballistic polymer, layer of tempered glass" and so on till desired thickness is achieved! there is nothing on the marked today that I would consider "Bullet Proof" because it is only good for 3-4 rounds fired at it then must be replaced due to fracture.. I would be more inclined to call it "Bullet resistant"

Any plastic can stop a bullet if it is thick enough. Smart answers aside, Polycarbinate and layered plastics are most widely used.

Lots of plastics can stop bullets. By definition, clay and mud are plastic and so are chemically made things like LEXAN, which is probably what you are thinking of but that is a trade name.... Polycarbonate is closer to what you are after and each ballistic protection manufacturer will have their own special recipe.

polycarbonate (name brand plexi-glass, I believe marko produces a similiar product as well) if formulated properly and thick enough (usualy laminated with special glues) will stop a bullet. lexan is a brand of acrylic that is often used for windows or around lights because its formulated to stop uv rays (and not turn yellow with age) but like most acrylic it's extreamly brittle and is not really impact resistant, in order to with stand a moderate caliber impact it would have to be very thick and heavy compared to polycarb.

and as a note the m-16 is not the only weapon to date designed to kill people, try most anything from sig-sauer, kahr, glock, IMI (who doesnt make a single sporting weapon) colt, ak, sks, m1, m-14 or any weapon designed for service use.

There is a new polyethurane (sp?) that has been tested to stop bullets better than kevlar and have 15 times more strength than steel.

very dense hdpe will stop a bullet with a fairly thin sheet. I don't know if it come in clear or not.

I've seen the military use Kevlar.I made parts for the Apache.

plexi glass (it is plastic and will stop some bullets)

Acrylic Sheet(bullet proof)

there is more

It's called, "Bulletproof " glass. Actually, it's polycarbonate.