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Cellulose Acetate Propionate (CAP)

CAP is a thermoplastic, further classified as a cellulosic plastic. It can have a moderately low tensile strength among the thermoplastics in the database.

The properties of CAP include two common variations. This page shows summary ranges across both of them. For more specific values, follow the links immediately below. The graph bars on the material properties cards further below compare CAP to: cellulosic 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

Elongation at Break

35 to 50 %

Flexural Modulus

1.2 to 1.9 GPa 0.17 to 0.28 x 106 psi

Flexural Strength

29 to 56 MPa 4.2 to 8.1 x 103 psi

Tensile Strength: Ultimate (UTS)

28 to 45 MPa 4.1 to 6.5 x 103 psi

Tensile Strength: Yield (Proof)

22 to 40 MPa 3.2 to 5.8 x 103 psi

Thermal Properties

Glass Transition Temperature

190 °C 370 °F

Heat Deflection Temperature At 1.82 MPa (264 psi)

65 to 80 °C 150 to 180 °F

Heat Deflection Temperature At 455 kPa (66 psi)

75 to 90 °C 170 to 190 °F

Specific Heat Capacity

1480 J/kg-K 0.35 BTU/lb-°F

Thermal Conductivity

0.25 W/m-K 0.14 BTU/h-ft-°F

Thermal Expansion

14 µm/m-K

Vicat Softening Temperature

85 to 110 °C 190 to 220 °F

Electrical Properties

Dielectric Constant (Relative Permittivity) At 1 MHz


Dielectric Strength (Breakdown Potential)

15 kV/mm 0.59 V/mil

Electrical Resistivity Order of Magnitude

16 10x Ω-m

Otherwise Unclassified Properties


1.2 g/cm3 75 lb/ft3

Refractive Index


Water Absorption After 24 Hours

1.4 to 1.7 %

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

9.1 to 22 MJ/m3

Strength to Weight: Axial

6.5 to 10 points

Strength to Weight: Bending

17 to 23 points

Thermal Diffusivity

0.14 mm2/s

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