Why is car windshield difficult to break?

The technology of making car window glass is increasingly developing to meet the needs of users such as safety, aesthetics, heat resistance and the ability to break to escape in case of danger. Currently, manufacturers mainly use two types of glass: laminated glass and tempered glass.

Laminated glass used in cars is usually made up of two layers of glass, with a layer of polyvinyl butyral (PVB) in between, which absorbs the impact from strong collisions. This design of laminated glass also helps reduce noise and block UV rays.

Glass in different positions on the car can be of the same or different types, depending on the purpose and goals of the manufacturer.

In an emergency, breaking a car window is easier than breaking a windshield. This is a design that has been carefully calculated and tested by car manufacturers.

Laminated glass is difficult to break with conventional tools, while tempered glass shatters into small pieces when subjected to external force.

Laminated glass is a type of glass formed by gluing many layers of glass together, with a layer of film made of PVB (Polyvinyl butyral) in the middle, which is durable and tough. When broken, this type of glass does not shatter into pieces but only cracks, but the pieces of glass still stick together. Therefore, it is often necessary to peel off a large piece if you want to break it.

Tempered glass is a type of glass that is tempered in a harsh environment, with the ability to withstand 7-10 times more force than normal glass. When broken, this type of glass will shatter into small pieces like pomegranate seeds, avoiding causing injury to the user.

Laminated glass is designed to reduce the risk of ejection of passengers in the event of an accident. Laminated glass is lighter than tempered glass, but stronger.

Meanwhile, the window and rear glass is tempered, created by heating regular glass panels and rapidly cooling them. Tempered glass has 5-10 times the strength and impact absorption capacity of regular glass, but is lower than laminated glass.

Tempered glass is commonly used for car doors and rear.

Why use laminated glass only in the front?

Using laminated glass on both sides of the door helps to better protect the occupants inside the car, reducing the risk of being thrown out in side collisions, and on the other hand helps to prevent glass breakage and theft.

However, in an emergency situation where people need to be taken out of the car, using laminated glass will make breaking the glass take longer.

On some expensive car models such as Rolls-Royce or Bentley, to increase safety and interior soundproofing quality, laminated glass is also used for the side doors, but only in the back seats and rear windows, while the front is still tempered glass, in case of emergency.

Information about the type of glass is usually written in the lower corner of the glass.