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General Purpose Polystyrene (GPPS)

GPPS is a grade of PS. The graph bars on the material properties cards below compare GPPS 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

Compressive (Crushing) Strength

90 MPa 13 x 103 psi

Elastic (Young's, Tensile) Modulus

2.9 GPa 0.42 x 106 psi

Elongation at Break

1.8 %

Flexural Modulus

3.2 GPa 0.46 x 106 psi

Flexural Strength

80 MPa 12 x 103 psi

Impact Strength: Notched Izod

19 J/m 0.35 ft-lb/in

Poisson's Ratio


Rockwell M Hardness


Tensile Strength: Ultimate (UTS)

44 MPa 6.3 x 103 psi

Thermal Properties

Glass Transition Temperature

100 °C 210 °F

Heat Deflection Temperature At 1.82 MPa (264 psi)

90 °C 190 °F

Maximum Temperature: Autoignition

360 °C 670 °F

Maximum Temperature: Decomposition

320 °C 610 °F

Maximum Temperature: Mechanical

70 °C 160 °F

Specific Heat Capacity

1250 J/kg-K 0.3 BTU/lb-°F

Thermal Conductivity

0.14 W/m-K 0.081 BTU/h-ft-°F

Thermal Expansion

98 µm/m-K

Vicat Softening Temperature

100 °C 210 °F

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz


Dielectric Strength (Breakdown Potential)

20 kV/mm 0.78 V/mil

Electrical Resistivity Order of Magnitude

15 10x Ω-m

Otherwise Unclassified Properties


1.0 g/cm3 65 lb/ft3

Limiting Oxygen Index (LOI)

18 %

Refractive Index


Water Absorption After 24 Hours

0.040 %

Common Calculations

Stiffness to Weight: Axial

1.5 points

Stiffness to Weight: Bending

45 points

Strength to Weight: Axial

12 points

Strength to Weight: Bending

26 points

Thermal Diffusivity

0.11 mm2/s

Thermal Shock Resistance

11 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