Toughened Glass
Thermally Treated Glass
A single piece of float or non-wired cast, annealed soda-lime silica glass, subjected to a thermal process which greatly increases its resistance to mechanical and thermal stress and gives it prescribed fragmentation characteristics.
There are three product families that make up thermally treated glass.
Thermally toughened glass
Thermally toughened glass has safer breakage behaviour when compared with annealed glass.
Thermally toughened safety glass can be manufactured from several annealed glass compositions. The thermally toughened products must comply with the appropriate standard:
EN 12150-1 for soda lime silicate glass
EN 12150-1 for borosilicate glass
EN 12150-1 for alkaline earth silicate glass
Properties of thermally toughened safety glass
Mechanical Strength
In general the strength can be increased to as much as four to five times that of the equivalent thickness of annealed glass. However, the thermal toughening process does not affect the modulus of elasticity of the product and care should be taken to limit excess deflection.
Thermal Strength
It offers greatly increased resistance to both sudden temperature changes and temperature differentials up to 200K compared with annealed glass, up to 40K. The stress characteristics of toughened safety glass, of normal soda-lime silica composition, are unchanged for continuing service up to 250°C
Fragmentation
In the event of breakage thermally toughened safety glass fractures into numerous small pieces, the edges of which are generally blunt.
Thermally toughened safety glass - Performance under accidental human impact
The thermally toughened safety glass has to be classified according to EN 12600; for its pendulum impact performance. This product can be used in critical locations (see BS 6262-4:2005)
Heat soaked thermally toughened safety glass
Heat soaked thermally toughened safety glass has a safer breakage behaviour when compared with annealed glass. It also has a known level of residual risk of spontaneous breakage arising from the possible presence of critical nickel sulphide (NiS) inclusions in the thermally toughened glass.
Heat soaked thermally toughened safety glass can be manufactured from several annealed glass compositions. The heat soaked thermally toughened products must comply with the appropriate standard:
EN 14179-1 for soda lime silicate glass
EN 15682-1 for alkaline earth silicate glass
Properties of heat soaked thermally toughened safety glass
These are the same as for a thermally toughened safety glass product.
Heat soaked thermally toughened safety glass - Performance under accidental human impact
The heat soaked thermally toughened safety glass has to be classified according to EN 12600; for its pendulum impact performance. This product can be used in critical locations (see BS 6262-4:2005)
Heat strengthened glass
Heat strengthened glass has a similar breakage behaviour as annealed glass. Heat strengthened glass is manufactured from soda lime silicate glass and must comply with EN 1863-1.
Properties of heat strengthened glass
Mechanical Strength
In general the strength can be increased to as much as one and a half times that of the equivalent thickness of annealed glass. However, the heat strengthening process does not affect the modulus of elasticity of the product and care should be taken to limit excess deflection.
Thermal Strength
It offers greatly increased resistance to both sudden temperature changes and temperature differentials up to 100K compared with annealed glass, up to 40K. The stress characteristics of toughened safety glass, of normal soda-lime silica composition, are unchanged for continuing service up to 200°C
Fragmentation
In the event of breakage heat strengthened glass breaks in manner similar to annealed glass.
Heat strengthened glass Performance under accidental human impact
Heat strengthened glass due to its breakage behaviour can not be classified according to EN 12600; for its pendulum impact performance. This product should not be used in critical locations (see BS 6262-4:2005)
Thermally treated glass - Processing restrictions
The characteristics of toughened and heat strengthened glass preclude any cutting or processing after manufacture. All holes and shapes must, therefore, be specified before ordering.
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