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  • 1
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    Effects of intermediate-energy electrons on mechanical and molecular properties of a polyetherimide (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An experiment, using 100-keV electrons and 10 to the 9th -rad doses, was conducted on Ultem polyetherimide film. Mechanical, electron paramagnetic resonance, and infrared spectroscopic data suggested that the radiation produced crosslinking and embrittlement of the material.
    Keywords: NONMETALLIC MATERIALS
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-31; 1293-129
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Infrared spectroscopic analysis of the effects of simulated space radiation on a polyimide (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Infrared spectroscopic techniques have been used to study the effects of electron radiation on the polyimide PMDA-p,p-prime- ODA. The radiation exposures were made at various dose rates, for a total dose approximately equal to that for 30 years of exposure to electron radiation in geosynchronous earth orbit. At high dose rates the major effect was probably the formation of a polyisoimide or a charged quaternary amine, and at the low dose rates the effect was a reduction in the amount or aromatic ether linkage. In addition, the effects of dose rate for a small total dose were studied. Elevated temperatures occurred at high dose rates and were, in part, probably the cause of the radiation product. The data suggest that dose rates for accelerated simulations of the space environment should not exceed 100,000 rads/sec.
    Keywords: NONMETALLIC MATERIALS
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  • 3
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    Radio-frequency electrical properties of some neat and metal-doped polyimides (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: As the size and complexity of aerospace systems increase, the uses of polymers are also expected to increase. Polyimides constitute one promising generic class of polymeric materials. They retain good mechanical and physical properties at higher temperatures and absorb less moisture than do the epoxies, which are the polymers most frequently used in present aerospace systems. The properties of these polyimide materials are, therefore, of considerable interest to the aerospace community. Of particular importance are the electrical properties because these properties relate to both electrical and structural applications.
    Keywords: NONMETALLIC MATERIALS
    Type: Studies of Molecular Properties of Polymeric Materials: Aerospace Environmental Effects on Three Linear Polymers; p 35-36
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    NASA TECHNICAL REPORTS
  • 4
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    Low-energy electron effects on tensile modulus and infrared transmission properties of a polypyromellitimide film (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Infrared (IR) spectroscopy and tensile modulus testing were used to evaluate the importance of experimental procedure on changes in properties of pyromellitic dianhydride-p,p prime-oxydianiline film exposed to electron radiation. The radiation exposures were accelerated, approximate equivalents to the total dose expected for a 30 year mission in geosynchronous Earth orbit. The change in the tensile modulus depends more on the dose rate and the time interval between exposure and testing than on total dose. The IR data vary with both total dose and dose rate. A threshold dose rate exists below which reversible radiation effects on the IR spectra occur. Above the threshold dose rate, irreversible effects occur with the appearance of a new band. Post-irradiation and in situ IR absorption bands are significantly different. It is suggested that the electron radiation induced metastable, excites molecular states.
    Keywords: NONMETALLIC MATERIALS
    Type: NASA-TM-81977 , L-13935
    Format: application/pdf
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  • 5
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    Electron and proton absorption calculations for a graphite/epoxy composite model (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Bethe-Bloch stopping power relations for inelastic collisions were used to determine the absorption of electron and proton energy in cured neat epoxy resin and the absorption of electron energy in a graphite/epoxy composite. Absorption of electron energy due to bremsstrahlung was determined. Electron energies from 0.2 to 4.0 MeV and proton energies from 0.3 to 1.75 MeV were used. Monoenergetic electron energy absorption profiles for models of pure graphite, cured neat epoxy resin, and graphite/epoxy composites are reported. A relation is determined for depth of uniform energy absorption in a composite as a function of fiber volume fraction and initial electron energy. Monoenergetic proton energy absorption profiles are reported for the neat resin model. A relation for total proton penetration in the epoxy resin as a function of initial proton energy is determined. Electron energy absorption in the composite due to bremsstrahlung is reported. Electron and proton energy absorption profiles in cured neat epoxy resin are reported for environments approximating geosynchronous earth orbit.
    Keywords: NONMETALLIC MATERIALS
    Type: NASA-TP-1568 , L-13073
    Format: application/pdf
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  • 6
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    Studies of molecular properties of polymeric materials: Aerospace environmental effects on three linear polymers (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The development of crystal handling techniques for reflection infrared spectroscopy and methods for the fabrication and testing of tensile specimens are discussed. Data from mechanical, ac and dc electrical, and electron paramagnetic resonance studies conducted to determine the effects of 0.1-MeV and 1.0-MeV electron radiation on Mylar, Kapton, Ultem, and metal-doped Ultem are presented. Total doses ranging from 1 X 10 to the 8 rads to 1 X 10 to the 10 rads and dose rates from 5 X 10 to the 7 rads/hr to 1 X 10 to the 9 rads/hr were employed. The results of a study on the effects of aircraft service-environment fluids on Ultem are also reported. The weights and mechanical properties of Ultem were evaluated before and after exposure to water, JP4, Skydrol, an antifreeze, and a paint stripper.
    Keywords: NONMETALLIC MATERIALS
    Type: NASA-TM-87532 , NAS 1.15:87532
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  • 7
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    Mechanism of electrical conductivity in an irradiated polyimide (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: A polyimide was exposed to 1.0 MeV electron radiation. The radiation-induced radical density and dc conductivity were measured at various post-irradiation times. The radiation-induced radical density was found to be correlated to the increased dc conductivity through a hopping model of conductivity. The post-irradiation radical species were identified.
    Keywords: NONMETALLIC MATERIALS
    Type: Journal of Physics and Chemistry of Solids (ISSN 0022-3697); 50; 7 19
    Format: text
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