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Low Expansion Borosilicate Glass (ASTM E438 Type I Class A)

Low expansion borosilicate is a grade of borosilicate glass. The graph bars on the material properties cards below compare low expansion borosilicate to other glass and glass-ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Compressive (Crushing) Strength

2000 MPa 290 x 103 psi

Elastic (Young's, Tensile) Modulus

68 GPa 9.9 x 106 psi

Flexural Strength

69 MPa 10 x 103 psi

Fracture Toughness

0.8 MPa-m1/2 0.73 x 103 psi-in1/2

Knoop Hardness


Poisson's Ratio


Tensile Strength: Ultimate (UTS)

280 MPa 41 x 103 psi

Thermal Properties

Maximum Temperature: Mechanical

360 °C 680 °F

Maximum Thermal Shock

160 °C 320 °F

Melting Onset (Solidus)

560 °C 1040 °F

Specific Heat Capacity

830 J/kg-K 0.2 BTU/lb-°F

Thermal Conductivity

1.2 W/m-K 0.68 BTU/h-ft-°F

Thermal Expansion

3.3 µm/m-K

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 MHz


Dielectric Strength (Breakdown Potential)

5.0 kV/mm 0.2 V/mil

Electrical Dissipation At 1 MHz


Electrical Resistivity Order of Magnitude

9.0 10x Ω-m

Otherwise Unclassified Properties


2.2 g/cm3 140 lb/ft3

Light Transmission Range

0.3 to 2.5 µm

Refractive Index


Common Calculations

Stiffness to Weight: Axial

17 points

Stiffness to Weight: Bending

61 points

Strength to Weight: Axial

35 points

Strength to Weight: Bending

43 points

Thermal Diffusivity

0.63 mm2/s

Thermal Shock Resistance

91 points

Followup Questions

Further Reading

ASTM E438: Standard Specification for Glasses in Laboratory Apparatus

Dictionary of Glass: Materials and Techniques, Charles Bray, 2002

Glass: Mechanics and Technology, Eric Le Bourhis, 2007

Handbook of Optical Constants of Solids, Edward D. Palik (editor), 1998

Ceramics and Composites: Processing Methods, Narottam P. Bansal and Aldo R. Boccaccini (editors), 2012