Effects of Radiation and Thermal Cycling on Teflon ® FEP

Dever, Joyce A.; Groh, Kim K. de; Banks, Bruce A.; Townsend, John W.

doi:10.1088/0954-0083/11/1/010

Cited by 37 publications

(32 citation statements)

References 4 publications

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“…A taskforce was formed to investigate why FEP was degrading in LEO. The work done represents perhaps the most comprehensive body of work on effects of the LEO environment on FEP and much of what was concluded can be applied to PVDF and copolymers [6,7,10,[58][59][60][61].…”

Section: Spacecraft Chargingmentioning

confidence: 99%

Characterization, performance and optimization of PVDF as a piezoelectric film for advanced space mirror concepts.

Jones¹,

Assink²,

Dargaville³

et al. 2005

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Piezoelectric polymers based on polyvinylidene fluoride (PVDF) are of interest for large aperture spacebased telescopes as adaptive or smart materials. Dimensional adjustments of adaptive polymer films depend on controlled charge deposition. Predicting their long-term performance requires a detailed understanding of the piezoelectric material features, expected to suffer due to space environmental degradation. Hence, the degradation and performance of PVDF and its copolymers under various stress environments expected in low Earth orbit has been reviewed and investigated. Various experiments were conducted to expose these polymers to elevated temperature, vacuum UV, γ-radiation and atomic oxygen. The resulting degradative processes were evaluated. The overall materials performance is governed by a combination of chemical and physical degradation processes. Molecular changes are primarily induced via radiative damage, and physical damage from temperature and atomic oxygen exposure is evident as depoling, loss of orientation and surface erosion. The effects of combined vacuum UV radiation and atomic oxygen resulted in expected surface erosion and pitting rates that determine the lifetime of thin films. Interestingly, the piezo responsiveness in the underlying bulk material remained largely unchanged. This study has delivered a comprehensive framework for material properties and degradation sensitivities with variations in individual polymer performances clearly apparent. The results provide guidance for material selection, qualification, optimization strategies, feedback for manufacturing and processing, or alternative materials. Further material qualification should be conducted via experiments under actual space conditions. 3 4 AcknowledgementsThe authors express their appreciation to Bruce Tuttle for use of equipment to measure the d 33 coefficients, Jonathan Campbell for use of the evaporation chamber, Mark Stavig for DMA measurements, Gary Zender for acquiring the SEM images, Ralph

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Section: Spacecraft Chargingmentioning

confidence: 99%

Characterization, performance and optimization of PVDF as a piezoelectric film for advanced space mirror concepts.

Jones¹,

Assink²,

Dargaville³

et al. 2005

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“…For example, in polymers with strong steric factors like atactic polystyrene, the amount of free volume in the structure, as shown by positron annihilation measurements, is increased by F/T cycling between ±20 to +120 C [3]. Fluorocarbons like perfluoropoly(ethylene co-propylene), FEP can withstand thousands of cycles between ±100 and +50 C as thin films (127 lm) in satellite applications with only minimal change in physical strength [4].…”

Section: Introductionmentioning

confidence: 99%

Effects of Deep Temperature Cycling on Nafion® 112 Membranes and Membrane Electrode Assemblies

McDonald¹,

2004

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A study was conducted to understand the physical and chemical changes in fuel cell membranes that result from Freeze/Thaw (F/T) cycling which might occur in electric vehicles. Nafion™ membranes and membrane electrode assemblies (MEA) were subjected to 385 temperature cycles between +80 °C and –40 °C over a period of three months to examine the effects on key properties. These studies were done on both compressed and uncompressed materials in the un‐humidified state. Although no catastrophic failures were seen, the analytical results shed some light on the relationship of temperature cycling to membrane structure, water management, ionic conductivity, gas permeability and mechanical strength. Changes in water swelling behavior and dry densities were noted and the effect on ionic conductivity and cell performance was examined. The impact on catalyst activity and structural integrity of MEAs was evaluated electrochemically.

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“…2. Because the insulator was made of Teflon Ò , it was thought that it might be attributed to the thermal stress and radiation of the electrons, ions and soft X-rays [18]. Hence it should be replaced by something like Al 2 O 3 or BN.…”

Section: Resultsmentioning

confidence: 99%