Properties of Borosilicate Glass

Chemical Composition
Physical Properties
SiO2 = 80.6% Coefficient of expansion (20°C–300°C) 3.3 x 10-6 K-1
B2O3 = 13.0% Density 2.23g/cm3
Na2O = 4.0% Refractive index (Sodium D line) 1.474
Al2O3 = 2.3% Dielectric constant (1MHz, 20°C) 4.6
Optical Information Specific heat (20°C) 750J/kg°C
Refractive index (Sodium D line) = 1.474 Thermal conductivity (20°C) 1.14W/m°C
Visible light transmission, 2mm thick glass = 92% Poisson’s Ratio (25°C – 400°C) 0.2
Visible light transmission, 5mm thick glass = 91% Young’s Modulus (25°C) 6400 kg/mm2