In recent years there has been much debate about the switch from using tempered glass for side, quarter, and rear windows, to now using laminated glass.
Glass that has been tempered, has undergone a special heat and cooling treatment that makes the glass stronger and shatter resistant. If the glass does shatter, it shatters in a less hazardous pattern that is supposed to reduce the risk of cutting your skin.
However, this is not always the case–which is why windshields are no longer made with tempered glass. (In fact, under federal law, all windshields must be made with laminated glass.) Simply put, it’s very difficult to consistently engineer glass that won’t cut you upon shattering. Since most side, back, and quarter windows of a vehicle aren’t likely to be impacted or break during an accident, this was not a primary concern of car manufacturers until the late 2000s.
The most notable benefit of using tempered glass rather than laminate glass is that in the event that your car has become submerged in water, you can very easily kick a tempered glass window out and escape the vehicle. This can also be handy if for any reason you have a child that becomes locked in your vehicle, and you need to get into the vehicle. (On the other hand, having car windows made of glass that can be shattered in a more easy manner makes the job of vandalists and crooks much simpler.)
In the late 2000’s car manufacturers began to make the shift to laminate glass for new safety concerns. Primarily, the concern was preventing the passengers inside of a vehicle from forcefully exiting during an accident. Being ejected from your vehicle is usually deadly, if not life-threatening. Your odds of surviving a car accident and having minor to moderate injuries, rather than serious or life threatening injuries, are much higher if you remain in the vehicle.
The process of creating laminate glass is more complex than tempered glass. First a series of dry and wet ingredients are combined and heated until they uniformly reach a liquid state, so that they combine and chemically bond. The particular ingredients are selected and combined in order to create a stronger glass that shatters in a non-hazardous pattern. The mixture is then poured into a warm mold, so that it takes the proper shape. After it initially sets, the newly created glass then undergoes hot and cold tempering, to further strengthen the chemical bonds.
After 2 sheets of glass are created in this manner, they are then fused together by sandwiching a piece of poly-vinyl butyral between them. This sandwich of glass and PVB is then put into the hot pressure chamber of an autoclave until they are firmly bonded together.
This process is vital to creating laminate glass, as it was created with the purpose of preventing the glass from shattering and allowing a passenger to exit the vehicle, in the event of a high impact accident. Also, in the case of a rollover, properly installed laminate car glass helps make up a significant percent of the car’s overall cabin strength. This means you are much less likely to be crushed if your car rolls over.
However, if for any reason you need to escape from or break into your vehicle, laminate glass is nearly impossible to puncture and shatter successfully.
Most car manufacturers believe that since events of escape/emergency break-in are far less likely than a high impact or rollover accident, that the benefits of using laminated glass far outweigh the dangers.
Although there has not yet been a legal mandate that requires all car windows and glass to be made with laminated glass, it is still highly likely that all of your car windows are made of laminate glass if you have a newer car.