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
Density
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