
Glass properties
Glass properties
The main characteristics of glass are transparency, heat resistance, pressure and breakage resistance and chemical resistance.
Mechanical properties
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Density : 2500 kg/m3
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Hardness : 470 HK
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Compression resistance : 800 - 1000 MPa
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Modulus of elasticity : 70 000 MPa
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Bending strength : 45 MPa
The main characteristics of glass are transparency, heat resistance, pressure and breakage resistance and chemical resistance.
Thermal properties
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Transformation range : 520 - 550°C
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Temp&Softening temperature : approx. 600°C
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Specific Heat : 0.8 J/g/K
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Thermal conductivity : 0.8W/mK
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Thermal expansion : 9.10-6 K-1
The main characteristics of glass are transparency, heat resistance, pressure and breakage resistance and chemical resistance.
Optical properties
Glass has several strong points concerning optical properties:
- It can be produced in large and homogeneous panes
- Its optical properties are not affected by ageing
- It is produced with perfectly flat and parallel surfaces
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Refractive index n = 1.52
The main characteristics of glass are transparency, heat resistance, pressure and breakage resistance and chemical resistance.
Technical Properties
Chemical resistance against
- Water = class 3 (DIN 52296)
- Acid = class 1 (DIN 12116)
- Alkaline = class 2 (DIN 52322 and ISO 695)
The surface of glass is affected if it is exposed for a long time to alkalis (and ammonia gases in damp air) in conjunction with high temperatures. Float glass will also react to compounds that contain hydrofluoric acid under normal conditions. These are used for treating glass surfaces.
Wear tests
- Abrasion tests (DIN 52347 and ISO 3537) The scattering of light the transmission of directed light striking the surface is evaluated.
- Light scatter increase for float glass is approx. 1% (after 1000 abrasion cycles). The permitted light scatter increase for vehicle safety glass (windshield) is 2% in Europe (ECE R43) and the USA (ANSI Z 26.1).
- Sand trickling process (DIN 52348 et ISO 7991). For this diagonal impact abrasion test, 3kg of sand with a 0.5/0.71mm particle size are trickled onto the surface to be tested, which is inclined at 45 y from a height of 1600mm. Measurement of wear is the reduced luminous density (according to DIN 4646 part 2).
- Reduced luminous density for float glass is approx. 4cd/m2lux.
- Micro scratch hardness for float glass is approx. 0.12N (Mar resistance-test).
The test was originally designed to determine the scratch hardness of plastics. A diamond point with 50 y cone angle and 15 mm point radius is drawn over the glass surface by applying different loads. The load at which a scratch is produced in the surface is a measurement of scratch hardness. This is not an accurate method; the influence of the tester must not be neglected.
The main characteristics of glass are transparency, heat resistance, pressure and breakage resistance and chemical resistance.