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What is Laminated Glass?
Laminated glass is an alternative to float glass, and is a type of safety glass that is designed to hold together if broken. It has many advantages over conventional float glass, from its enhanced strength to its ability to be repaired in the case of minor damage. While laminated glass has a significant number of applications, cutting laminated glass can be a complicated process.
How is Laminated Glass Made?
As the name suggests, laminated glass comprises layers of glass. The standard configuration is a layer of flexible polymeric material sandwiched between two layers of glass. Laminated glass is produced using one of two methods:
- Poly Vinyl Butyral (PVB) laminated glass
- Cast in Place (CIP) laminate.
Poly Vinyl Butyral (PVB) Laminated Glass
PVB laminated glass is produced using a heat and pressure process, sandwiching a flexible interlayer between layers of glass. Generally, the interlayer has a thickness of 0.38mm, except for applications such as automotive windscreens, which use a 0.76mm thick interlayer.
Cast in Place (CIP) Laminated Glass
CIP laminated glass is manufactured by pouring resin into the cavity between two adjacent panes of glass. Interlayer thicknesses of 1.0mm to 1.5mm are common for CIP laminated glasses.
Cutting Laminated Glass
There are two ways of cutting laminated glass. The first method uses tables specialized for cutting laminated glass, and the second method includes the use of vertically-inclined saw frames.
When using cutting tables, both sides of the laminated glass are cut at the same time. After moving the glass, the interlayer is melted. The glass is then able to be parted manually.
In the case of saw frames, a water-cooled circular saw moves in an almost vertical frame and is used for glass with two plastic interlayers. It can cut large panes of glass in approximately 15 to 20 minutes.
A third method involves cutting the glass layers and then melting the plastic interlayer with methylated spirits, but as it can be a dangerous process to set alight to the interlayer, cutting tables or vertical saws are considered the safer and preferred option for cutting laminated glass.
Laminated Glass vs. Standard Float Glass
Laminated glass has the advantage over standard glass in that it will not shatter, as the polymeric interlayer is not subject to brittle failure as the glass is. Furthermore, the interlayer provides a barrier against penetration.
Additionally, minor damage to laminated glass used in vehicle windshields can be repaired. Repairs aim to ensure that the driver has a clear view and the finish is smooth to not interfere with wiper blades. To fix laminated glass, the glass is drilled at the point of fracture to reach the lamination layer in the middle. The air in the damaged area is removed, and it is replaced with resin that is then cured with ultraviolet light.
Tinted interlayer materials can be used to help minimize heat and UV transmission, while the polymeric material also acts as a sound deadening layer, damping sound transmission in a manner equivalent to glass twice as thick.
Key Properties of Laminated Glass
- Increased safety factor compared to standard float glass
- Resistant to shattering
- Improved acoustic damping properties compared to standard float glass.
Many building applications require a glass exterior but at the same time need to minimize sound transmission, such as a restaurant on a busy street. For this reason, laminated glasses with good acoustic dampening properties are used. These types of glass are also used because of the security benefits they provide, outlined below.
Laminated glasses are used for windscreens for all forms of transport from cars to trains. They are typically PVB laminated glass using a thicker interlayer of about 0.76mm. This gives the material an excellent resistance to penetration from rocks or high winds, for instance, while at the same time providing excellent light transmission. The plastic interlayer is also designed to hold panes of glass together if breakages do occur, increasing safety for both drivers and passengers.
Many applications require transparent panels for viewing purposes. At the same time, they may also need to keep out burglars or bullets and provide a safer alternative to float glass. In these cases, laminated glasses can give the solution due to their resistance to shattering and penetration. Laminated glass is often used in high-security buildings, including banks, embassies, and jewelry shops. Safety applications, for instance, shower screens, may use thicknesses as low as 6.38mm (comprising of two layers of 3mm thick glass with a 0.38mm interlayer), while burglar resistant grades may utilize similar structures, but thicker glass panels. Bullet resistant glasses range in thickness from 24mm to 53mm, depending on what type of weapon they are trying to stop. These glasses may involve several layers of glass each separated by a polymeric interlayer.
Although cutting laminated glass can prove problematic, and some methods include unsafe practices such as lighting spirits on fire to melt the laminate layer, it has a multitude of uses. It boasts enhanced security levels when compared with conventional float glass and has found applications in both domestic and commercial builds.
Sources and Further Reading
This article was updated on 7th February, 2019.