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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of a thermally imidized soluble polyimide film (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 3107-3122 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A soluble aromatic poly (amic acid) film was converted to a soluble polyimide by staging at 25°C intervals to 325°C and characterized at each interval by several analytical methods. The behavior observed was consistent with an interpretation that a reduction occurred in molecular weight of the poly (amic acid) during the initial stages of cure before the ultimate molecular weight was achieved as a polyimide. This interpretation was supported by the results of solution viscosity, gel permeation chromatography, low angle laser light scattering photometry, and infrared spectroscopy analyses. The results of this study serve to increase our fundamental understanding of how polyimides are thermally formed from poly (amic acid)s.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281117
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    Paper (German National Licenses)
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  • 2
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    Characterization of selected LDEF-exposed polymeric films (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The characterization of selected experimental and commercially available thin polymeric films which received 10 months of exposure to the LEO environment on the Long Duration Exposure Facility is reported. The visual appearance of most specimens changed due to exposure. However, except for a silicon-containing copolymer film, chemical characterization including infrared, thermal, and X-ray photoelectron analyses showed that the molecular structure of the surviving material had not changed significantly in response to exposure. Surface texturing due to atomic oxygen erosion was documented using various microscopic analyses. The possibility of continued post-exposure degradation of some polymeric materials is proposed.
    Keywords: NONMETALLIC MATERIALS
    Type: In: International SAMPE Symposium and Exhibition, 37th, Anaheim, CA, Mar. 9-12, 1992, Proceedings (A93-15726 04-23); p. 159-171.
    Format: text
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  • 3
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    Scanning Tunneling Microscopy analysis of space-exposed polymer films (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The characterization of the surface of selected space-exposed polymer films by Scanning Tunneling Microscopy (STM) is reported. Principles of STM, an emerging new technique for materials analysis, are reviewed. The analysis of several films which received up to 5.8 years of low Earth orbital (LEO) exposure onboard the NASA Long Duration Exposure Facility (LDEF) is discussed. Specimens included FEP Teflon thermal blanket material, Kapton film, and several experimental polymer films. Ultraviolet and atomic oxygen-induced crazing and erosion are described. The intent of this paper is to demonstrate how STM is enhancing the understanding of LEO space environmental effects on polymer films.
    Keywords: NONMETALLIC MATERIALS
    Type: In: International Instrumentation Symposium, 39th, Albuquerque, NM, May 2-6, 1993, Proceedings (A93-54351 24-35); p. 445-455.
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  • 4
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    Analysis of a space-exposed thermoplastic resin (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The chemical characterization of a thermoplastic resin exposed to the low Earth orbit (LEO) environment for 10 months and for 5.8 years is reported. The resin, processed as a thick film and as a matrix for a graphite fiber reinforced composite, few exposed in the RAM direction on the NASA Long Duration Exposure Facility (LDEF). Differences attributable to environmental exposure were detected in infrared spectra and in various molecular weight parameters of film after 10 months in LEO. Those effects were not as apparent in composites after 5.8 years in LEO. Increased exposure to atomic oxygen toward the end of the LDEF mission probably scrubbed these effects from specimens exposed for 5.8 years. The intent of this study is to increase our fundamental understanding of space environmental effects on polymeric materials and to develop a benchmark for enhancing our methodology for and understanding of the ground-based simulation of space environmental effects.
    Keywords: NONMETALLIC MATERIALS
    Type: In: International SAMPE Technical Conference, 24th and International SAMPE Metals and Metals Processing Conference, 3rd, Toronto, Canada, Oct. 20-22, 1992, Proceedings. Vol. 24 (A93-53376 23-23); p. T174-T185.
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  • 5
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    Characterization of a thermally imidized soluble polyimide film (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A soluble aromatic poly(amic acid) film was converted to a soluble polyimide by staging at 25 deg intervals to 325 C and characterized at each interval by several analytical methods. The behavior observed was consistent with an interpretation that a reduction occurred in molecular weight of the poly(amic acid) during the initial stages of cure before the ultimate molecular weight was achieved as a polyimide. This interpretation was supported by the results of solution viscosity, gel permeation chromatography, low angle laser light scattering photometry and infrared spectroscopy analysis. The results serve to increase the fundamental understanding of how polyimides are thermally formed from poly(amic acids).
    Keywords: NONMETALLIC MATERIALS
    Type: Journal of Polymer Science: Polymer Chemistry Edition (ISSN 0360-6376); 28; 3107-312
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  • 6
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    The effect of Low Earth Orbit exposure on some experimental fluorine and silicon-containing polymers (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Several experimental fluorine and silicon-containing polymers in film form were exposed to low Earth orbit (LEO) on a Space Shuttle flight experiment (STS-46, Evaluation of Oxygen Interaction with Materials, EOIM-3). The environmental parameters of primary concern were atomic oxygen (AO) and ultraviolet (UV) radiation. The materials were exposed to 2.3 plus or minus 0.1 x 10(exp 20) oxygen atoms/sq cm and 30.6 UV sun hours during the flight. In some cases, the samples were exposed at ambient, 120 C and 200 C. The effects of exposure on these materials were assessed utilizing a variety of characterization techniques including optical, scanning electron (SEM) and scanning tunneling (STM) microscopy, UV-visible (UV-VIS) transmission, diffuse reflectance infrared (DR-FTIR), x-ray photoelectron (XPS) spectroscopy, and in a few cases, gel permeation chromatography (GPC). In addition, weight losses of the films, presumably due to AO erosion, were measured. The fluorine-containing polymers exhibited significant AO erosion and exposed films were diffuse or 'frosted' in appearance and consequently displayed dramatic reductions in optical transmission. The silicon-containing films exhibited minimum AO erosion and the optical transmission of exposed films was essentially unchanged. The silicon near the exposed surface in the films was converted to silicate/silicon oxide upon AO exposure which subsequently provided protection for the underlying material. The silicon-containing epoxies are potentially useful as AO resistant coatings and matrix resins as they are readily processed into carbon fiber reinforced composites and cured via electron radiation.
    Keywords: NONMETALLIC MATERIALS
    Type: NASA. Goddard Space Flight Center, Eighteenth Space Simulation Conference: Space Mission Success Through Testing; p 157-175
    Format: application/pdf
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  • 7
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    LDEF polymeric materials: 10 months versus 5.8 years of exposure (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The chemical characterization of several polymeric materials which received 10 months of exposure and 5.8 years of exposure on a Row 9 Long Duration Exposure Facility (LDEF) experiment (A0134) is reported. Specimens include fluorinated ethylene propylene (FEP) teflon film, polysulfone film, and graphite fiber reinforced epoxy amd polysulfone matrix composites. The responses of these materials to the two LEO exposures are compared. The results of infrared, thermal, x-ray photoelectron, and scanning electron microscope analyses are reported. Solution property measurements of various molecular weight parameters are presented for the thermoplastic polysulfone materials. Molecular level effects attributable to exposure that were present in 10-month exposed specimens were not found in 5.8-year exposed specimens. This result suggests that increased atomic oxygen fluence toward the end of the LDEF mission may have eroded away selected environmentally induced changes in surface chemistry for 5.8-year exposure specimens.
    Keywords: NONMETALLIC MATERIALS
    Type: LDEF: 69 Months in Space. Part 3: Second Post-Retrieval Symposium; p 827-847
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  • 8
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    LDEF thermal control coatings post-flight analysis (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The NASA Long Duration Exposure Facility (LDEF) provided a unique flight opportunity for conducting experiments in space and return of these experiments to Earth for laboratory evaluation. The results of one of these experiments, S0010, Exposure of Spacecraft Coatings, in which selected spacecraft thermal control coatings were exposed to the low-Earth orbital (LEO) environment on LDEF are reported. The objective of the experiment is to evaluate the response of thermal control coatings to LEO exposure, which includes atomic oxygen, ultraviolet and particulate radiation, meteoroid and debris, vacuum, and temperature cycling.
    Keywords: NONMETALLIC MATERIALS
    Type: LDEF: 69 Months in Space. Part 3: Second Post-Retrieval Symposium; p 1093-1097
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  • 9
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    Characterization of selected LDEF: Exposed polymer films and resins (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The Long Duration Exposure Facility (LDEF) provided a unique environmental exposure of a wide variety of materials. The effects of 5 years and 10 months of Low-Earth Orbit (LEO) exposure of these materials to atomic oxygen, ultraviolet and particulate radiation, meteoroid and debris, vacuum, contamination, and thermal cycling is providing a data base unparalleled in the history of space environment research. Working though the Environmental Effects on Materials Special Investigation Group (MSIG), a number of polymeric materials in various processed forms have been assembled from LDEF investigators for analysis at the NASA Langley Research Center. This paper reports the status of on-going chemical characterization of these materials.
    Keywords: NONMETALLIC MATERIALS
    Type: LDEF Materials Workshop 1991, Part 1; p 357-389
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  • 10
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    Chemical characterization of selected LDEF polymeric materials (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The chemical characterization of selected polymeric materials which received exposure on the LDEF is reported. The specimens examined include silvered fluorinated ethylene propylene (FEP) teflon thermal blanket material, polysulfone matrix resin/graphite fiber reinforced composites, and several high performance polymer films. These specimens came from numerous LDEF locations and, thus, received different environmental exposures. The results of infrared, thermal, x ray photoelectron, and various solution property analyses have shown no significant change at the molecular level in the polymer that survived exposure. However, scanning electron and scanning tunneling microscopies show resin loss and a texturing of the surface of some specimens which resulted in a change in optical properties. The potential effect of a silicon containing molecular contamination on these materials is addressed. The possibility of continued post-exposure degradation of some polymeric films is also proposed.
    Keywords: NONMETALLIC MATERIALS
    Type: LDEF: 69 Months in Space. First Post-Retrieval Symposium, Part 2; p 687-703
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