# Rigid Thermoset Polyurethane (RPU)

RPU is a thermoset plastic. It has the lowest density among thermoset plastics. In addition, it has the highest ductility and the highest heat capacity. The graph bars on the material properties cards below compare RPU to other thermoset plastics (top) 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

2.2 *GPa* 0.32 *x 10 ^{6} psi*

Elongation at Break

90 *%*

Flexural Modulus

2.0 *GPa* 0.29 *x 10 ^{6} psi*

Flexural Strength

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

Tensile Strength: Ultimate (UTS)

60 *MPa* 8.7 *x 10 ^{3} psi*

## Thermal Properties

Maximum Temperature: Autoignition

380 *°C* 720 *°F*

Maximum Temperature: Decomposition

270 *°C* 520 *°F*

Specific Heat Capacity

1750 *J/kg-K* 0.42 *BTU/lb-°F*

Thermal Conductivity

0.19 *W/m-K* 0.11 *BTU/h-ft-°F*

Thermal Expansion

63 *µm/m-K*

Vicat Softening Temperature

120 *°C* 240 *°F*

## Other Material Properties

Density

1.2 *g/cm ^{3}* 75

*lb/ft*

^{3}Dielectric Strength (Breakdown Potential)

19 *kV/mm* 0.74 *V/mil*

Electrical Resistivity Order of Magnitude

13 *10 ^{x} Ω-m*

## Common Calculations

Stiffness to Weight: Axial

1.0 *points*

Stiffness to Weight: Bending

36 *points*

Strength to Weight: Axial

14 *points*

Strength to Weight: Bending

28 *points*

Thermal Diffusivity

0.090 *mm ^{2}/s*

Thermal Shock Resistance

31 *points*

## Followup Questions

## Further Reading

Polyurethanes: Science, Technology, Markets, and Trends, Mark F. Sonnenschein, 2015

Thermosets: Structure, Properties and Applications, Qipeng Guo (editor), 2012

Modern Plastics Handbook, Charles A. Harper (editor), 1999

Plastics Materials, 7th ed., J. A. Brydson, 1999