# Polylactic Acid (PLA, Polylactide)

PLA is a thermoplastic, further classified as a polyester plastic. It has the highest heat capacity and the lowest thermal conductivity relative to other polyester plastics. The graph bars on the material properties cards below compare PLA to: polyester plastics (top), all thermoplastics (middle), and the entire database (bottom).

## Mechanical Properties

Elastic (Young's, Tensile) Modulus

3.5 *GPa* 0.51 *x 10 ^{6} psi*

Elongation at Break

6.0 *%*

Flexural Modulus

4.0 *GPa* 0.58 *x 10 ^{6} psi*

Flexural Strength

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

Shear Modulus

2.4 *GPa* 0.35 *x 10 ^{6} psi*

Tensile Strength: Ultimate (UTS)

50 *MPa* 7.3 *x 10 ^{3} psi*

## Other Material Properties

Density

1.3 *g/cm ^{3}* 78

*lb/ft*

^{3}Glass Transition Temperature

60 *°C* 140 *°F*

Heat Deflection Temperature At 455 kPa (66 psi)

65 *°C* 150 *°F*

Melting Onset (Solidus)

160 *°C* 320 *°F*

Specific Heat Capacity

1800 *J/kg-K* 0.43 *BTU/lb-°F*

Thermal Conductivity

0.13 *W/m-K* 0.075 *BTU/h-ft-°F*

## Common Calculations

Stiffness to Weight: Axial

1.6 *points*

Stiffness to Weight: Bending

40 *points*

Strength to Weight: Axial

11 *points*

Strength to Weight: Bending

24 *points*

Thermal Diffusivity

0.058 *m ^{2}/s*

## Followup Questions

## Further Reading

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

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

SPI Plastics Engineering Handbook of the Society of the Plastics Industry, Inc., 5th ed., Michael L. Berins (editor), 2000