Menu (ESC)

Polybutylene Terephthalate (PBT)

PBT is a thermoplastic, further classified as a polyester plastic. It has the lowest mechanical heat stability among the polyester plastics in the database.

The properties of PBT include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare PBT 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

Elastic (Young's, Tensile) Modulus

2.7 to 8.7 GPa 0.39 to 1.3 x 106 psi

Elongation at Break

2.5 to 43 %

Flexural Modulus

2.6 to 9.1 GPa 0.38 to 1.3 x 106 psi

Flexural Strength

79 to 210 MPa 11 to 30 x 103 psi

Tensile Strength: Ultimate (UTS)

58 to 140 MPa 8.4 to 20 x 103 psi

Thermal Properties

Glass Transition Temperature

40 °C 100 °F

Heat Deflection Temperature At 1.82 MPa (264 psi)

4.0 °C 39 °F

Heat Deflection Temperature At 455 kPa (66 psi)

160 °C 310 °F

Maximum Temperature: Autoignition

380 °C 720 °F

Maximum Temperature: Decomposition

380 °C 720 °F

Melting Onset (Solidus)

230 °C 440 °F

Specific Heat Capacity

1040 to 1200 J/kg-K 0.25 to 0.29 BTU/lb-°F

Otherwise Unclassified Properties


1.3 to 1.5 g/cm3 83 to 95 lb/ft3

Limiting Oxygen Index (LOI)

20 %

Common Calculations

Stiffness to Weight: Axial

1.1 to 3.2 points

Stiffness to Weight: Bending

35 to 45 points

Strength to Weight: Axial

12 to 25 points

Strength to Weight: Bending

25 to 38 points

Followup Questions

Further Reading

Reinforced Plastics Durability, Geoffrey Pritchard (editor), 1999

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

Advanced Materials in Automotive Engineering, Jason Rowe (editor), 2012