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			40°C approx.
Thermal Expansion Coefficient			100 x 10^-6 °C^-1
Volume Resistivity			> 10^16 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 +260°C				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 27°C.