Mechanical Properties of Teflon® FEP Retrieved from the Hubble Space Telescope

Teflon® FEP (fluorinated ethylene propylene) surfaces on the Hubble Space Telescope (HST) have experienced significant degradation in mechanical properties during nearly ten years of exposure in the low Earth orbit environment. This paper describes results of mechanical properties testing of Teflon® FEP materials exposed on HST for 9.7 years between launch and the third servicing mission (SM3A) and for 2.8 years between the second servicing mission (SM2) and SM3A. The results of tensile testing, bend testing and microscopic examination of crack morphology are described. The effects of post-retrieval heating and air compared with vacuum storage on the mechanical properties of the FEP surfaces are described as they significantly affect the interpretation of the results regarding the durability of FEP on HST. This paper provides comparisons of the properties of FEP surfaces retrieved during SM3A to previously reported results for FEP materials retrieved during the first servicing mission (SM1) and SM2. The environmental exposure conditions for the HST exposed materials are also described.