Laminated glass is used for car windshields and in places where safety is important. It consists of two layers of glass with a PVB interlayer that prevents shattering. Invented by French chemist Edouard Benedictus, it was first used in gas mask eyepieces during World War I. The production process involves pressing the layers together and heating them to bond. Additional layers increase strength, and it is also used for artistic applications.
Laminated glass is a type of safety glass commonly used for automobile windshields. It consists of two layers of glass with a film layer, called an interlayer, between them. The glass is designed this way to prevent it from shattering into sharp pieces when hit by an object or when the car is in an accident.
The interlayer in the glass is a film of a strong but flexible material known as polyvinyl butyral (PVB). In the event of glass breakage, the two layers are held together by the PVB, allowing the sheet as a whole to bend and absorb the impact. This feature is especially important for car windshields as, ideally, the film will prevent objects from penetrating through the glass and injuring the car’s occupants. Laminated glass is also used in prisons, jewelry stores, hospitals and other places where safety is paramount.
French chemist Edouard Benedictus invented laminated glass in 1903. As is sometimes the case with inventions, his was inspired by an accident in his laboratory. One of her glass bottles had been coated with a plastic compound called cellulose nitrate. It fell and broke, but it didn’t shatter.
Based on this discovery, Benedictus fabricated a glass-plastic composite that he intended to use to reduce injuries in road crashes. Car manufacturers, however, did not adopt his invention for many years. In fact, the first widespread use of this type of glass was in the eyepieces of gas masks used in World War I. Today, though, it’s a much more common sight in a variety of locations.
The production of laminated glass has become standardized as the demand for the product has increased. Typically, two layers of glass with a thickness of about 0.12 inch (3 mm) are placed on either side of the PVB layer which is 0.015 inch (0.38 mm) thick. The rollers press the layers together to push out any air pockets. The glass is then heated to 158°F (70°C) in a pressurized oil bath to permanently bond all the layers together.
Additional layers of glass and PVB will increase the strength of the material. For example, the glass that forms the front widows of airliners is often three 0.23-inch (6 mm) glass plates with thick layers of PVB between them. Some types are also used for artistic applications, such as glass sculptures and mosaics.
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