Windshield glass, also known as laminated glass, is made up of two pieces of glass glued to a thin layer of vinyl in between. When laminated windshields are broken, the two pieces separate and fall away from each other instead of shattering into small pieces that can become projectiles.
What Are the Unique Properties of Windshield Glass?
The vinyl layer in windshield glass is known as the interlayer and it’s used to add strength to the window. The interlayer provides tensile strength to prevent crack propagation across the windshield when hit by flying debris or impacted by an object on your car’s hood or trunk (e.g., when someone throws something at your car).
Most of the time, this layer is 0.015 inches thick, but depending on the make and model of your vehicle, the thickness can be as much as 0.060 inches thick. When glass is manufactured, this layer typically has a coating on it called priming that protects the glass and helps resist scratches. If you have ever scratched your windshield, you might have noticed that there was a line underneath where you scratched it; this is because there are usually multiple layers of glazing between the two surfaces that help protect against scratches and chips in the exterior surface of your windshield (i.e., outer laminate).
Another factor affecting how much strength a laminated windshield has over regular glass is how much tempering pressure was applied during manufacturing; tempering refers to heating up an object until its molecules are heated so much that they lose their shape (plastic deformation) before cooling down again into new crystalline structures which increases its strength by up to 50%.
Why Is Windshield Glass Made in This Way?
The purpose of the vinyl interlayer is to add another dimension to the strength and process of breaking a windshield. The interlayer is a thin layer of material that attaches to both sides of the glass and provides extra support for the glass in an accident.
The interlayer can be made with multiple materials, but it’s commonly made from polyvinyl butyral (PVB), or “plastic.” It’s called plastic because it resembles plastic more than glass. This material makes up only about 5% of the weight of your windshield, but it plays a crucial role in maintaining vehicle safety in accidents.
If you have ever seen a cracked windshield before, you may have noticed that it looks like spiderwebs on your car window. Those aren’t actually spiderwebs; they’re air pockets created when small pieces of broken bits fly off during impact.
With this design, even if you hit something hard enough to crack your glass, it won’t spider web or shatter into tiny pieces that can fall into your car.