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General Borosilicate Glass

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Description

Borosilicate glasses have a remarkably low coefficient of thermal expansion and are therefore very resistant to thermal shock. Their main glass-forming constituents are substantial amounts of silica and boron trioxide. Usually, one distinguishes between non-alkaline earth borosilicate glass, alkaline-earth-containing borosilicate glass and high-borate borosilicate glass.

Properties

Electrical

Dielectric constant εr

4.1 - 6.7 [-] at 20 °C

at 1MHz

Loss tangent tanδ

6E-5 - 0.01 [-] at 20 °C

at 1MHz

General

Density ρ

2.1 - 2.8 g/cm³ at 20 °C

Mechanical

Elastic modulus E

50 - 70 GPa at 20 °C

Hardness, Knoop, HK2 HK2

400 - 480 [-] at 20 °C

Poisson's ratio ν

0.2 - 0.22 [-] at 20 °C

Shear modulus G

2650 - 27000 GPa at 20 °C

Optical

Refractive index nd

1.47 - 1.52 [-]

Thermal

Annealing temperature Tanneal

470 - 640 °C

Coefficient of thermal expansion α

3.2E-6 - 7.38E-6 1/K at 300 °C

Glass transition temperature Tg

440 - 560 °C

Thermal conductivity λ

0.96 - 1.2 W/(m·K) at 20 °C

Vicat softening temperature Tsoft

460 - 840 °C