# Glycol-Modified Polyethylene Terephthalate (PETG, PET-G)

PETG is a thermoplastic, further classified as a polyester plastic. The graph bars on the material properties cards below compare PETG to: polyester plastics (top), all thermoplastics (middle), 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

55 *MPa* 8.0 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

2.2 *GPa* 0.32 *x 10 ^{6} psi*

Flexural Modulus

2.1 *GPa* 0.31 *x 10 ^{6} psi*

Flexural Strength

77 *MPa* 11 *x 10 ^{3} psi*

Impact Strength: Notched Izod

77 *J/m* 1.5 *ft-lb/in*

Rockwell R Hardness

120

Shear Strength

62 *MPa* 9.0 *x 10 ^{3} psi*

Tensile Strength: Ultimate (UTS)

53 *MPa* 7.7 *x 10 ^{3} psi*

## Thermal Properties

Glass Transition Temperature

81 *°C* 180 *°F*

Heat Deflection Temperature At 1.82 MPa (264 psi)

69 *°C* 160 *°F*

Heat Deflection Temperature At 455 kPa (66 psi)

73 *°C* 160 *°F*

Melting Onset (Solidus)

140 *°C* 280 *°F*

Specific Heat Capacity

1200 *J/kg-K* 0.29 *BTU/lb-°F*

Thermal Conductivity

0.29 *W/m-K* 0.17 *BTU/h-ft-°F*

Thermal Expansion

68 *µm/m-K*

## Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

2.6

Dielectric Constant (Relative Permittivity) At 1 MHz

2.4

Dielectric Strength (Breakdown Potential)

16 *kV/mm* 0.63 *V/mil*

## Otherwise Unclassified Properties

Density

1.3 *g/cm ^{3}* 79

*lb/ft*

^{3}Refractive Index

1.6

Water Absorption After 24 Hours

0.2 *%*

## Common Calculations

Stiffness to Weight: Axial

1.0 *points*

Stiffness to Weight: Bending

34 *points*

Strength to Weight: Axial

12 *points*

Strength to Weight: Bending

25 *points*

Thermal Diffusivity

0.19 *mm ^{2}/s*

Thermal Shock Resistance

25 *points*

## Followup Questions

## Further Reading

SPI Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., 5th ed., Michael L. Berins (editor), 2000

Modern Plastics Handbook, Charles A. Harper (editor), 1999

Plastics Materials, 7th ed., J. A. Brydson, 1999