# 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 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

68 *GPa* 9.9 *x 10 ^{6} psi*

Flexural Strength

69 *MPa* 10 *x 10 ^{3} psi*

Fracture Toughness

0.8 *MPa-m ^{1/2}* 0.73

*x 10*

^{3}psi-in^{1/2}Knoop Hardness

510

Poisson's Ratio

0.21

Tensile Strength: Ultimate (UTS)

280 *MPa* 41 *x 10 ^{3} 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

5.4

Dielectric Strength (Breakdown Potential)

5.0 *kV/mm* 0.2 *V/mil*

Electrical Dissipation At 1 MHz

0.0046

Electrical Resistivity Order of Magnitude

9.0 *10 ^{x} Ω-m*

## Otherwise Unclassified Properties

Density

2.2 *g/cm ^{3}* 140

*lb/ft*

^{3}Light Transmission Range

0.3 to 2.5 *µm*

Refractive Index

1.5

## 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 *mm ^{2}/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