Toughened Laminated Glass is also known as Toughened Safety Glass or Tempered Toughened Glass. It is about four to five times stronger than the Normal Annealed Glass.
The manufacturing of this glass is complicated, it is thermally heat-treated (564° C to 620°C) and chemically balanced for better handling of the compressive and tensile stresses. Due to thermal heat treatment, it is better known as Tempered Toughened Glass. The tempering process subjected to intense heating of glass and then the glass is put in the chemical process for rapid cooling during manufacture.
It was invented by a French chemist Edouard Benedictus in 1903. Edouard invented this type of glass after being inspired by a car accident where the victim was injured by the shattering pieces of glass windshield. In 1905, John Crewe Wood from the Swindon, England patented the use of Toughened Laminated Glass as windshields. But it took a long time for the automobile industry to accept it as a windshield option, as the cost was comparatively higher than the normal windshield used at that time. But in 1930, the British parliament passed a Road Traffic Act to make the Toughened Laminated Glass windshield compulsory for new cars.
With this, the windshield breaks but the glass doesn’t shatter in the car or on the driver. This is due to the bonding between several sheets of annealed panes of glass with the sheets of plastic interlayer in between them. Now, if there is an accident that causes the windshield to shatter, the windshield stays together with the glass only having web-like cracks. Glass is also not easy to break or cut if there is an accident and if passengers need to be rescued.
A typical Toughened Laminated Glass manufacturing is like a sandwich, where two or more layers o f glass are attached, and each glass is linked to the other layer with laminate interlayer [Thermoplastic Polyurethane (TPU), Polyvinyl Butyral (PVB), Ethylene-Vinyl Acetate (EVA)]. The interlayer bonds the glass sheets, functioning even when the glass is broken. It also prevents the glass from being shattered into large, razor edge pieces.
Nowadays, normal uses include situations where human interference is needed to manage the possibility of glass shattering as this could cause mishappenings. Other applications also include situations in need of bullet-resistant glass, sound insulation glass, architecture designs, military helmets, and bullet-resistant shields.
Properties of Toughened Laminated Glass:
- Radiation Reflective Index of 1.50
- Able to filter 99% of UV rays
- Specific Gravity of 1.07
- If glass layers shatter, then the pieces stay together
Applications of Toughened Laminated Glass:
- Making complex design, e.g. fighter planes cockpit windshield
- Noise reduction window and door
- Security and safety glasses, e.g. for banks and jewelry shops
- Provides insulation against radiation, noise and fire (withstand high temperature up to 250° C).
- UV protection, particularly when used for space missions/International Space Station
- For architecture designs, e.g. Zhangjiajie Grand Canyon Glass Bridge
- Provides blast protection
- Bullet-resistant glass for windshield, first used during World War II for soldiers’ helmets
- For display and exhibition areas
- Frameless glass doors, furniture, glass shelves and glass table tops