7740 (Pyrex)

Pyrex 7740 is Corning's trade name borosilicate glass. Because of its low coefficient of thermal expansion, the material is useful in high temperature applications, and is also heat shock resistant. Pyrex is also resistant to acid and has high optical transmission over a wide wavelength range. The low alkali content of Pyrex also makes this glass ideal for high-purity laboratory applications. Pyrex glass can be used as a coatings substrate, and can also be polished by Valley to standard and custom thicknesses. Valley also provides thin polished Pyrex glass wafers.

Mechanical Properties
Density (at 20 °C/68 °F): 2.23 g/cm³
Knoop Hardness: 418 kg/mm²
Young's Modulus: 64 GPa
Flexural Strength: 69 MPa @R.T.
Poisson's Ratio: 0.20
Shear Modulus: 2.67 x 10³ kg/mm²

Thermal Properties
Thermal Coefficient of Expansion (0/300 °C): 32.5 x 10^-7/°C
Thermal Conductivity: 1.1 W/mK @R.T.
Specific Heat: 0.18 cal/g-°C @R.T.
Strain Point: 510°C/950°F
Annealing Point: 560°C/1040°F
Softening Point: 821°C/1509.8°F

Optical Properties
Refractive Index (l=589.3nm): 1.473
Optical Transmission

Chemical Properties
Hydrolytic resistance: class 1
Acid resistance: class 1
Alkali resistance: class 2

Electrical Properties
Dielectric Constant: E=4.6 1MHz @R.T.
Dielectric Strength: 0.5 kV/mm
Resistivity: 8 x 10¹⁰ ohm/cm @R.T.