# Polymethylmethacrylate (PMMA, Acrylic)

PMMA is an otherwise-unclassified thermoplastic material. The graph bars on the material properties cards below compare PMMA to: otherwise unclassified thermoplastics (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

120 *MPa* 18 *x 10 ^{3} psi*

Elastic (Young's, Tensile) Modulus

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

Elongation at Break

4.0 *%*

Flexural Strength

110 *MPa* 16 *x 10 ^{3} psi*

Impact Strength: Notched Izod

74 *J/m* 1.4 *ft-lb/in*

Rockwell M Hardness

93

Shear Modulus

1.7 *GPa* 0.25 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

71 *MPa* 10 *x 10 ^{3} psi*

## Thermal Properties

Glass Transition Temperature

110 *°C* 230 *°F*

Heat Deflection Temperature At 1.82 MPa (264 psi)

96 *°C* 200 *°F*

Maximum Temperature: Autoignition

320 *°C* 600 *°F*

Maximum Temperature: Decomposition

360 *°C* 670 *°F*

Melting Onset (Solidus)

180 *°C* 350 *°F*

Specific Heat Capacity

1260 *J/kg-K* 0.3 *BTU/lb-°F*

Thermal Conductivity

0.19 *W/m-K* 0.11 *BTU/h-ft-°F*

Thermal Expansion

76 *µm/m-K*

Vicat Softening Temperature

90 *°C* 190 *°F*

## Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 Hz

3.6

Dielectric Strength (Breakdown Potential)

30 *kV/mm* 1.2 *V/mil*

## Otherwise Unclassified Properties

Density

1.2 *g/cm ^{3}* 74

*lb/ft*

^{3}Limiting Oxygen Index (LOI)

17 *%*

Refractive Index

1.5

## Common Calculations

Stiffness to Weight: Axial

1.5 *points*

Stiffness to Weight: Bending

42 *points*

Strength to Weight: Axial

17 *points*

Strength to Weight: Bending

32 *points*

Thermal Diffusivity

0.13 *mm ^{2}/s*

Thermal Shock Resistance

21 *points*

## Followup Questions

## Further Reading

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