Thread Starter


Joined Oct 5, 2010

I found some goggles and it has a mark on it "GUARANTEE UNBREAKABLE POLYCARBONATE LENS". what does it mean?

I wanna use it for some of my experiments. pls. help

the catapult


Joined Mar 24, 2008
The lenses are made of bullet proof glass, AKA lexan.

You are looking at safety glasses, which should be worn when machining or using power tools.

Going for the mad scientist look?


Joined Jul 7, 2009
Polycarbonate is not "bullet-proof glass" -- that's a different animal. Polycarbonate is a type of plastic, typically clear. It's a great material because of its impact resistance and toughness, especially compared to acrylic like Plexiglas. You'll commonly see trade names used to identify the plastic, such as Lexan for polycarbonate. I like to use it for router fixtures in the shop, as it's much more scratch resistant than acrylic and much harder to break. It makes great safety glasses, both to protect against impacts and I've found by measurements that it's a good attenuator of UV, so I also use it for working around UV sources.


Joined Mar 24, 2008
I have quite a bit of experience with Lexan. To quote Wikipedia,

Lexan is a registered trademark for SABIC Innovative Plastics' (formerly General Electric Plastics) brand of polycarbonate resin thermoplastic. Polycarbonate polymer is produced by reacting bisphenol A with carbonyl dichloride, also known as phosgene. Lexan is the brand name for polycarbonate sheet and resin in a wide range of grades. Applications are mainly in three domains–building (glazing and domes), industry (machine protection and fabricated parts) and communication and signage. Common usages include space and sports helmets, clear high performance windshields and aircraft canopies, and bullet resistant windows.

It is used in combat robotics, such as Battlebots, for the panels of the arena.

A quote from your article points out ...

Bullet-resistant glass is usually constructed using polycarbonate, thermoplastic, and layers of laminated glass. The aim is to make a material with the appearance and clarity of standard glass but with effective protection from small arms. Polycarbonate designs usually consist of products such as Armormax, Makroclear, Cyrolon, Lexan or Tuffak, which are often sandwiched between layers of regular glass.[2]

Now where does the bulletproofing come from?

An interesting property, when the Lexan was penetrated, it did not crack, it melted.
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Joined Apr 30, 2011
When a safety glass or goggle is marked unbreakable, that's marketing language that means it meets the requirements of the latest version of ANSI Z87.1.


Joined Apr 17, 2010
I don't know much but, my glasses are made up of polycarbonate (as per the manufacturer) which is really unbreakable to some extend. It has fallen down so many times but it didn't got any scratch on it.I am sure if I use a hammer it will break but I think it will not break like a glass.

My glasses also have some sort of protective stuff for monitor,TV screens(UV protection may be) so when I see any reflection of any object on my glasses its color changes to green or violet but I am sure it is not related to polycarbonate.


Joined Sep 7, 2009
The resistance of bulletproof glass comes from the lamination of glass and polycorbonate. Glass is very strong in compression, even when shattered, and the polycarbonate holds everything together. I think the glass shattering absorbs some of the energy as well.