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Optical Glass Properties

Properties of 7740 Pyrex Glass

7740 Pyrex Glass
Pyrex 7740 glass 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. 7740 Pyrex glass 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. 7740 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 7740 Pyrex glass wafers.

Principal Uses

Filter lenses, wafers and substrates, tubing, labware, consumer glass products, heat shields, electrical insulators, first surface mirrors

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.