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

Dever, Joyce A.; Groh, Kim K. de; Messer, Russell; McClendon, Mark W; Viens, Michael J.; Wang, L Len; Gummow, Jonathan D.

doi:10.1088/0954-0083/13/3/330

Cited by 16 publications

(12 citation statements)

References 5 publications

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“…From the overall geometry it is reasonable to assume that the maximum tensile stresses from thermal expansion appear tangential to the V2 SADA axis, leading to the observed 4V2-directed longitudinal cracking. On the anti-solar-facing surfaces very fine fractures of FEP surfaces were observed, similar to pattern described in Dever et al [12]. The solar-facing FEP surfaces between row C and D were strongly discoloured (figures 1 and 2(c)) and featured an ochre, rough (RMS roughness of 13.6 4 0.6 3m, as compared to around 3.7 3m on the other HST/SA2 surfaces and below 3 3m for pristine material) surface, which may originate from erosion and contamination.…”

Section: Optical Investigationsupporting

confidence: 86%

Surface and Bulk Degradation of Teflon® FEP Retrieved from the Hubble Space Telescope Solar Arrays

Möser

Semprimoschnig

Eesbeek

et al. 2008

High Performance Polymers

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Teflon R 1 fluorinated ethylene propylene (FEP) is used on the Hubble Space Telescope (HST) as the outer layer of multilayer insulation (MLI) blankets. During space shuttle servicing missions (SM) to HST through thickness cracks were observed in the FEP layers. Material brought to Earth for investigation showed signs of severe degradation. During servicing mission 3B, the 4th servicing mission to HST in March 2002, the second pair of European Space Agency ESA built solar arrays was retrieved and flown back to Earth after 8.25 years in space. Samples of the MLI thermal control material were taken from the solar array drive arm (SADA) and investigated for surface and bulk degradation. The MLI was enveloped around the SADA and thus allowed the examination of FEP degradation in dependence of the orientation of space exposed areas with respect to the Sun. Therefore micrographs of FEP surfaces and fractographs of through thickness cracks were taken and the solar absorptance 1 S and the normal emittance 2 N was measured on the entire MLI. Differential scanning calorimetrical analyses as well as electron spectroscopy for chemical analyses were conducted to analyze chemical changes of the bulk polymer and the surface layer, respectively. Tensile properties and mass losses of the space exposed material were evaluated as well. Results of the investigated thermal control material are compared with samples exposed on the ground to thermal cycling, soft X-rays and vacuum ultra-violet radiation as well as to previously reported results on space-exposed FEP. The paper thus gives further insight into the mechanism and processes contributing to the on orbit degradation of Teflon R 1 FEP and correlates the presented data with exposure levels and exposure conditions. Downloaded from 430 M. MOSER ET AL. Figure 1. Right: Hubble Space Telescope with axis system. The position of the investigated multilayer insulation (MLI) on the solar array drive arm (SADA) is indicated1 Left: SADA MLI with grid system.

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Section: Optical Investigationsupporting

confidence: 86%

Surface and Bulk Degradation of Teflon® FEP Retrieved from the Hubble Space Telescope Solar Arrays

Möser

Semprimoschnig

Eesbeek

et al. 2008

High Performance Polymers

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“…The exposure levels for the various materials retrieved are affected by the solar activity, and it should be noted that there was a solar minimum between the SM2 to SM3A time period. More details of environmental exposures are provided in [6,7].…”

Section: The Hst Environmentmentioning

confidence: 99%

Thermal Contributions to the Degradation of Teflon® FEP on the Hubble Space Telescope

Groh¹,

Dever²,

Sutter³

et al. 2001

High Performance Polymers

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Metallized Teflon ® fluorinated ethylene propylene (FEP) thermal control material on the Hubble Space Telescope (HST) is degrading in the space environment. Teflon ® FEP insulation was retrieved during servicing missions, which occurred in 1993, 1997 and 1999. During the second servicing mission (SM2), the 5 mil aluminized-FEP (Al-FEP) outer layer of multilayer insulation (MLI) covering the telescope was found to be cracked in many locations around the telescope. Teflon ® FEP retrieved during SM2 was more embrittled than the FEP retrieved 2.8 years later from a different location, during the third servicing mission (SM3A). Studies have been conducted to understand the degradation of FEP on HST, and the difference in the degree of degradation of FEP from each of the servicing missions. The retrieved SM2 material experienced a higher temperature extreme during thermal cycling (200 • C) than the first servicing mission (SM1) and SM3A materials (upper temperature of 50 • C), therefore an investigation on the effects of heating FEP was also conducted. Samples of pristine FEP and SM1, SM2 and SM3A retrieved FEP were heated to 200 • C and evaluated for changes in properties. Heating at 130 • C was also investigated because FEP bi-stem thermal shields are expected to cycle to a maximum temperature of 130 • C on-orbit. Tensile, density, x-ray diffraction crystallinity and differential scanning calorimetry data were evaluated. It was found that heating pristine FEP caused an increase in the density and practically no change in tensile properties. However, when as-retrieved space samples were heated, the density increased and the tensile properties decreased. Upon heating, all samples experienced an increase in crystallinity, with larger increases in the space-exposed FEP. These results indicate that irradiation of FEP in space causes chain scission, resulting in embrittlement, and that excessive heating allows increased mobility of space-environment-induced scissioned chains. Thermal exposure was therefore found to have a major impact on the extent of embrittlement of FEP on HST.

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“…Fluorinated ethylene-propylene copolymer (FEP) Teflon, commonly used as a thermal control material on spacecraft, degrades upon exposure to the LEO environment (5)(6)(7)(8)(9)(10)(11)(12). Many studies have used both space environments and ground-based test facilities in order to unravel the erosion mechanism of FEP Teflon.…”

Section: Introductionmentioning

confidence: 99%

Erosion of FEP Teflon and PMMA by VUV Radiation and Hyperthermal O or Ar Atoms

Zhang

Lindholm

Brunsvold

et al. 2009

ACS Appl. Mater. Interfaces

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A combination of beam-surface-scattering, quartz-crystal-microbalance, and surface-recession experiments was conducted to study the effects of various combinations of O atoms [in the O((3)P) ground state], Ar atoms, and vacuum ultraviolet (VUV) light on fluorinated ethylene-propylene copolymer (FEP) Teflon and poly(methyl methacrylate) (PMMA). A laser-breakdown source was used to create hyperthermal beams containing O and O(2) or Ar. A D(2) lamp provided a source of VUV light. O atoms with 4 eV of translational energy or less did not react with a pristine FEP Teflon surface. Volatile O-containing reaction products were observed when the O-atom energy was higher than 4.5 eV, and the signal increased with the O-atom energy. Significant erosion of FEP Teflon ( approximately 20% of Kapton H) was observed when it was exposed to the hyperthermal O/O(2) beam with an average O-atom energy of 5.4 eV. FEP Teflon and PMMA that were exposed to VUV light alone exhibited much less mass loss. Collision-induced dissociation by hyperthermal Ar atoms also caused mass loss, similar in magnitude to that caused by VUV light. There were no observed synergistic effects when VUV light or Ar bombardment was combined with O/O(2) exposure. For both FEP Teflon and PMMA, the erosion yields caused by simultaneous exposure to O/O(2) and either VUV light or Ar atoms could be approximately predicted by adding the erosion yield caused by O/O(2), acting individually, to the erosion yield caused by the individual action of either VUV light or Ar atoms.

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

Cited by 16 publications

References 5 publications

Surface and Bulk Degradation of Teflon® FEP Retrieved from the Hubble Space Telescope Solar Arrays

Surface and Bulk Degradation of Teflon® FEP Retrieved from the Hubble Space Telescope Solar Arrays

Thermal Contributions to the Degradation of Teflon® FEP on the Hubble Space Telescope

Erosion of FEP Teflon and PMMA by VUV Radiation and Hyperthermal O or Ar Atoms

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