A.17.15. PTFE (Teflon, Halon, Fluon, Hostaflon)

PRODUCT

Type

Thermoplastic.

Chemical Composition

Polytetrafluoroethylene.

Manufacturer

Several (DuPont USA, Hoechst D, Montecatini I, etc.)

EXPERIENCE & AVAILABILITY

Development Status

Commercial Product

Cost Range

Medium

Lot Reproducibility

Excellent

Space Experience

Excellent

GENERAL PROPERTIES (Physical, Mechanical, Thermal, Electrical, Optical)

Nature

Typical Value

Remarks

Specific Gravity

2.15

 

Hardness

55

Shore D

Tensile Strength

25 MPa

 

Tensile Modulus

420 MPa

 

Thermal Conductivity

0.25 W m -1 C -1

 

Specific Heat

1 J g-1 C -1

40C approx.

Thermal Expansion Coefficient

100 x 10-6 C -1

 

Volume Resistivity

> 1016 W m

 

Dielectric Constant

2.1

60 Hz

Dissipation Factor

0.0002

60 Hz

Dielectric Strength

18.9 kV/mm

ASTM D149

PROPERTIES RELEVANT TO SPACE USE

Nature

Typical Value

Type of Test

Temperature Range

Cryogenic to +260C

Long term

Outgassing

TML = 0.05%, RML = 0.02%, CVCM = 0.0%

ECSS-Q-70-02

Oxygen Index

95

ECSS-Q-70-21

Ionising Radiation

0.1 Mrad

Threshold damage under vacuum.

Toxicity/Offgassing

Pass

NASA NHB 8060-1A

Flammability

Pass (30% O2)

NASA NHB 8060-1B

SPECIAL RECOMMENDATIONS

          PTFE has a strong tendency to creep and is unable to sustain constant high load. Creep may occur during thermal cycling.

          All PTFE-insulated wires and cables tested up to now have been found acceptable for space use.

          PTFE is rather sensitive to radiation and its use outside a spacecraft, particularly in high-radiation zones (Van Allen belts, geostationary orbit) requires special testing.

          Volume change associated with a change of crystallinity occurs between approx. 22 to 27C.