A.17.14. PETP (Mylar, Melinex, Terphane, ...)
PRODUCT
Type		Thermoplastic film.
Chemical Composition		Polyethylene Terephthalate.
Manufacturer		Several (DuPont USA, ICI UK, La Cellophane France, ...)
EXPERIENCE & AVAILABILITY
Development Status				Commercial Product
Cost Range				Very Low
Lot Reproducibility				Excellent
Space Experience				Extensive
GENERAL PROPERTIES (Physical, Mechanical, Thermal, Electrical, Optical)
Nature			Typical Value			Remarks
Specific Gravity			1.4
Tensile Strength			210 MPa
Tear Strength			0.787 kg/mm
Folding Endurance			> 100 000			ASTM D2176
Thermal Expansion Coefficient			30 x 10^-6 °C^-1
Thermal Conductivity			0.61 W m^-1 °C^-1
Specific Heat			1.3 J g^-1 °C^-1
Volume Resistivity			10^16 W m
Dielectric Constant			3.2			50 Hz, 25°C
Dissipation Factor			0.002			50 Hz, 25°C
Dielectric Strength			280 kV/mm
Refractive Index			1.64
PROPERTIES RELEVANT TO SPACE USE
Nature	Typical Value				Type of Test
Temperature Range	-180 to +150°C				Long term
Outgassing	TML = 0.3%, RML = 0.1%, CVCM = 0.03%				ECSS-Q-70-02
Oxygen Index	31				ECSS-Q-70-21
Ionising Radiation	10 Mrad				Mechanical properties
UV Radiation	Unstable
Water Absorption	0.6%				Immersion
Toxicity/Offgassing	Pass				NASA NHB 8060-1A
Flammability	Burnt				NASA NHB 8060-1B
SPECIAL RECOMMENDATIONS
· Aluminised films (1 or 2 faces) exist in the trade and are extensively used in space programmes since Al protects the plastic against destruction by unfiltered UV light. · Sizes available are down to 3mm thick and up to 300 cm wide, depending on the vendor. · Flammability depends on thickness and configuration. · PETP is etched by atomic oxygen in low earth orbit at a rate of approx. 3.4 x 10^-24 cm^3/atom.