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