# 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 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

2.9 *GPa* 0.42 *x 10 ^{6} psi*

Elongation at Break

1.8 *%*

Flexural Modulus

3.2 *GPa* 0.46 *x 10 ^{6} psi*

Flexural Strength

80 *MPa* 12 *x 10 ^{3} psi*

Impact Strength: Notched Izod

19 *J/m* 0.35 *ft-lb/in*

Poisson's Ratio

0.4

Rockwell M Hardness

65

Tensile Strength: Ultimate (UTS)

44 *MPa* 6.3 *x 10 ^{3} 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

2.5

Dielectric Strength (Breakdown Potential)

20 *kV/mm* 0.78 *V/mil*

Electrical Resistivity Order of Magnitude

15 *10 ^{x} Ω-m*

## Otherwise Unclassified Properties

Density

1.0 *g/cm ^{3}* 65

*lb/ft*

^{3}Limiting Oxygen Index (LOI)

18 *%*

Refractive Index

1.6

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 *mm ^{2}/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