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Polystyrene (PS)

PS is a thermoplastic, further classified as a styrenic plastic. It has a moderately low density and can have a moderately low tensile strength among thermoplastics.

The properties of PS 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 PS to: styrenic 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

1.9 to 2.9 GPa 0.28 to 0.42 x 106 psi

Elongation at Break

1.8 to 40 %

Flexural Strength

62 to 80 MPa 9.0 to 12 x 103 psi

Impact Strength: Notched Izod

19 to 45 J/m 0.35 to 0.85 ft-lb/in

Poisson's Ratio

0.4 to 0.41

Tensile Strength: Ultimate (UTS)

32 to 44 MPa 4.6 to 6.3 x 103 psi

Thermal Properties

Glass Transition Temperature

100 °C 210 °F

Maximum Temperature: Autoignition

360 to 420 °C 670 to 780 °F

Maximum Temperature: Decomposition

320 to 330 °C 610 to 620 °F

Maximum Temperature: Mechanical

70 °C 160 °F

Specific Heat Capacity

1250 to 1400 J/kg-K 0.3 to 0.33 BTU/lb-°F

Thermal Conductivity

0.14 to 0.22 W/m-K 0.081 to 0.13 BTU/h-ft-°F

Thermal Expansion

80 to 98 µm/m-K

Vicat Softening Temperature

100 to 110 °C 210 to 220 °F

Electrical Properties

Dielectric Strength (Breakdown Potential)

18 to 20 kV/mm 0.7 to 0.78 V/mil

Electrical Resistivity Order of Magnitude

14 to 15 10x Ω-m

Otherwise Unclassified Properties

Density

1.0 g/cm3 65 lb/ft3

Limiting Oxygen Index (LOI)

18 %

Water Absorption After 24 Hours

0.040 to 0.080 %

Common Calculations

Stiffness to Weight: Axial

1.0 to 1.5 points

Stiffness to Weight: Bending

40 to 45 points

Strength to Weight: Axial

8.5 to 12 points

Strength to Weight: Bending

22 to 26 points

Thermal Diffusivity

0.11 to 0.15 mm2/s

Thermal Shock Resistance

11 to 15 points

Followup Questions

Further Reading

ASTM D883: Standard Terminology Relating to Plastics

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

CRC Materials Science and Engineering Handbook, 4th ed., James F. Shackelford et al. (editors), 2015