Laminated Glass

During the manufacture of laminated glass, two or more panes of float glass are firmly bonded together with one or more highly elastic polyvinylbutyral (PVB) films. Alternatively, resin can be poured between two sheets of glass which are separated by spacers, and the resin is then cured. This process is called cast-in-place (CIP). The normal transparency of the glass may be slightly reduced depending on the thickness of the glass. Laminated glass is a non-splintering glass as the plastic film(s) hold the fragments of glass in place when the glass is broken, thus reducing the possibility of personal injury to a minimum.

 

There are several categories of laminated glass: safety glass, anti-bandit glass, bullet-resistant glass, fire-resistant glass and sound-control glass. The thickness and the number of layers of glass, and the types of interlayer, are designed to produce the required properties.

 

Laminated safety glass
Laminated safety glass normally consists of two layers of glass bonded with polyvinylbutyral (PVB) foil. This is a standard product which is used to promote safety in areas where human contact and potential breakage are likely. The tear-resistant foil makes it difficult to penetrate the glass, thus giving enhanced security against breakage and break-in. Even when safety glass is broken, the security of the room is maintained. Laminated safety glass is always used for overhead glazing for safety and security reasons. Building regulations insist on its use in certain situations.

Normal maximum sizes of glazing units using laminated glass

Normal maximum sizes of glazing units using laminated glass

Laminated safety glass can be use in these areas: glazed doors and patio doors; door sidelights; shops; all low-level glazing; balustrades; bathing and shower screens; anywhere that children play and may fall against the glass, or where there is a high traffic volume, e.g. entrance areas in community buildings, schools and playschools.

 

Laminated anti-bandit glass
Laminated anti-bandit glass is the most suitable material for providing complete security in protective glazing systems. Anti-bandit glass can be made with two glass layers of different thicknesses bonded with PVB foil, or with three or more glass layers of different glass thicknesses bonded with standard or reinforced PVB foil. Additional security can be provided by incorporating alarm bands, or wires connected to an alarm system.

 

One side of this glass will withstand repeated blows from heavy implements such as bricks, hammers, crowbars, pickaxes etc. There may be crazing in the area of impact, but the tough, resilient PVB inter-layers absorb the shock waves, stop any collapse of the pane and prevent loose, flying fragments of glass. Even after a sustained attack, the glass continues to provide visibility and reassurance, as well as protection from the elements. Additional security can be achieved by bonding the glass to the framing members so that the frame and the glass cannot be separated during an attack. Normally, the side of the expected attack is the external side. Only in law courts should the side of the expected attack be on the inside. It is not permissible to change the orientation of the glazing without good reason.

 

Laminated anti-bandit glass can be use in these areas: shops; display cases; museums; kiosks and ticket offices; banks; post offices; building societies; wages and rent offices; etc.

 

Blast-resistant glass
Safety and anti-bandit glass can also be used to provide protection against bomb attack and blast. The glass performs in two ways. First, it repels any bomb which is thrown at it, causing it to bounce back at the attacker, and second, under the effects of a blast it will deform and crack, but the glass pieces remain attached, reducing the likelihood of flying splinters.

 

Bullet-resistant glass
For protection against gunshots, a build-up of multiple layers is required, the overall thickness (20-50 mm) depending on the classification required. This glass incorporates up to four layers of glass, some of different thicknesses, inter-layered with PVB. When attacked, the outer layers on the side of the attack are broken by the bullet and absorb energy by becoming finely granulated. The inner layers absorb the shock waves. A special reduced-spatting grade of glass can be used to minimize the danger of glass fragments flying off from the rear face of the glass. Even after an attack, barrier protection is maintained and visibility (apart from the impact area) is unaffected. Bullet-resistant classifications are based on the type of weapon and calibre used, e.g. handgun, rifle or shotgun.

Bullet-resistant glass can be use in these areas: banks; post offices; building societies; betting offices; wages and rent offices; cash desks; security vehicles; embassies; royal households; political and government buildings; airports; etc.

 

Base on Architects’ Data by Ernst and Peter Neufert

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