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What is Bullet Proof Glass?

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  • Edited By: C. Wilborn
  • Last Modified Date: 19 September 2016
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Bullet proof glass refers to any type of glass that is built to stand up against being penetrated by most bullets. In the industry itself, this glass is referred to as bullet-resistant glass, because there is no feasible way to create consumer-level glass that can truly be proof against bullets. There are two main types of bullet proof glass: that which uses laminated glass layered on top of itself, and that which uses a polycarbonate thermoplastic.

Laminated bullet proof glass has been used since World War II, and although quite effective, it is also relatively heavy and thick. Generally it is about four inches (100 mm) thick, although it may be as thick as eight inches (200 mm) for some applications. Thin sheets of glass are laminated together using a bonding agent, usually polyurethane or ethylene-vinyl.

The more common type of modern bullet resistant glass uses a polycarbonate thermoplastic layered between glass. This layer, which comes under many trade names, including Lexan, Armormax, and Makroclear, is built to withstand blunt force. It distributes the force relatively evenly, so that if it is hit with a hammer, a fist, or an axe, it would repel the object easily.

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By itself, this polycarbonate layer could easily be penetrated by a streamlined bullet. When layered with glass, however, it becomes much more effective. As the bullet hits the glass layer, it flattens out as it breaks the glass, which by itself would not stop it from passing through. When it encounters the polycarbonate layer, it has been flattened such that the plastic is able to repel it. Multiple layers of glass and plastic are layered on top of each other to ensure that the bullet is adequately flattened and slowed to be completely stopped.

In recent years, a type of bullet proof glass has become popular in deployments such as armored cars, where it is desirable for those on the inside to be able to fire at those on the outside, while still being protected from incoming bullets. One-way bullet resistant glass uses a two-layered approach to ensure bullets can only penetrate from one direction. The outside of the window is made up of brittle glass, which shatters on impact, while the inside of the window is made up of a more flexible layer that gives under direct force. When a bullet is fired from the inside, it penetrates the flexible layer, then shatters a small area of the outer layer and makes its way through. When a bullet is fired from the outside, however, it hits the brittle layer first, which shatters and distributes its force, so that it is insufficient to penetrate the flexible layer.

The field of bullet proof glass is constantly developing, and there are a number of military projects underway to create lighter-weight, more defensive forms of bullet proof glass. One of the most promising is the use of aluminum oxynitride in the outer layer, in place of a polymer layer. This allows for much lighter, more resistant glass that can be used in military assault vehicles and aircraft.

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submariner
Post 4

@ PelesTears- Thanks for the advice, but the neighborhood we live in is very nice. the city is what is undergoing a rash of crimes. I live in a city that has been hard hit by the recession and housing crisis. Many of the houses near my neighborhood have gone into foreclosure, and the rate of burglary is on the rise. In the last year, numerous acts of violence have appeared on the local news, and recently there was a shooting between young adults at an apartment complex a few blocks from our property. One of the houses in our neighborhood was even broken into by armed thieves while the residents were home sleeping.

I have a gun, but with

kids, my gun is also locked away (not very accessible in an emergency). We like our neighborhood, and expect things to turn around in the next few years, but in the meantime, I would like the peace of mind knowing that my family is safe while I am away on business. Thank you for the info on the availability and cost of bullet proof glass though. I appreciate it.
PelesTears
Post 3

@ Framemaker- I would think that if you can afford to buy bulletproof glass, you would also consider moving to a new neighborhood. That is beside the point, but it is an alternative to being in an area where gun violence and breaking and entering is common.

Anyone can buy or install bullet proof glass. The pricing is really dependent on the application, and what you are trying to stop, but you can expect it to start somewhere around $5 per square inch uninstalled. For your home, you should probably seek the services of a company that specializes in installing bullet barriers and glass for corporate offices, high priority civilians, and Businesses. If you need to find one of these

companies, you should search online for someone in your area. There are companies that can install everything from safe rooms and panic rooms to bullet resistant furniture. You can have bullet resistant fiberglass netting installed within your walls, and bullet proof windows for one or all rooms in your house. Expect to pay dearly though.
FrameMaker
Post 2

What are some other applications for bulletproof and security glass? Is it something that I can buy for my home, or is it only available to certain people like military, law enforcement and government? How expensive are bulletproof windows? I am a homeowner near an area that has had a recent rash of gun violence and home invasions. I was thinking about adding reinforced glass and doors to the lower level of my home as well as putting a wall around my property. I do not want to compromise the safety of my family so I thought that this might be a better and more aesthetically pleasing option than putting bars on my windows. Any information would be appreciated. Thanks!

anon53142
Post 1

How flexible is it?

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