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Polyhydroxybutyrate (PHB)

PHB is a thermoplastic, further classified as a polyester plastic. It has a moderately low tensile strength among the polyester plastics in the database. The graph bars on the material properties cards below compare PHB 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

1.3 GPa 0.19 x 106 psi

Elongation at Break

7.5 %

Flexural Strength

20 MPa 2.9 x 103 psi

Tensile Strength: Ultimate (UTS)

30 MPa 4.4 x 103 psi

Thermal Properties

Heat Deflection Temperature At 1.82 MPa (264 psi)

60 °C 140 °F

Maximum Temperature: Mechanical

120 °C 250 °F

Melting Onset (Solidus)

180 °C 350 °F

Vicat Softening Temperature

58 °C 140 °F

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

3.0

Electrical Resistivity Order of Magnitude

14 10x Ω-m

Otherwise Unclassified Properties

Density

1.3 g/cm3 78 lb/ft3

Water Absorption After 24 Hours

0.75 %

Common Calculations

Stiffness to Weight: Axial

0.58 points

Stiffness to Weight: Bending

29 points

Strength to Weight: Axial

6.7 points

Strength to Weight: Bending

17 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