Embrittlement of Polymers in Space

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PPT for my first seminar on "polymers in space"

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  • Hi imgeevarghesegeorge & im currently doing my sixth sem in polymer science and engg & im here to present my review seminar…
  • ..on “embrittlement of polymers after 13 months of exposure to outer space”.. Which is basically a low earth orbit - LEO - experiment conducted by national aeronautics and space administration A.K.A. NASA..My reference research paper was originally presented and prepared for the 10th international space conference on protection of materials and structures from the space enviornment..
  • ..All info that im sharing here belongs to Scientific And Technical information program or STI organization founded by nasa..It provides access to the nasa aeronautics and space database, its technical reports server, thus providing one of the largest collections of aeronautical and space science STI in the world..
  • Objective of this experiment is to measure the embrittlement of 37 thin film polymers after low earth orbit space exposure..The polymers where flown on-board the International Space Station and exposed to the LEO space environment as a part of the materials International Space station Experiment 5 – MISSE 5 …
  • ..The need of the experiment. Inorder to understand the “space environment” induced degradation of spacecraft materials.. It is considered essential when designing durable and stable spacecraft components..
  • Misse is a series of spaceflight experiments designed to test the performance and durability of materials and devices exposed to the leo space enviornment.Misse consists of 11 flight experiment trays (10 passive experiment carriers and 1 small tray) that are mounted to the ISS..they may be aranged in zenith/nadir OR a ram/wake orientation..
  • Misse5 polymer samples were taken from PEACE – Polymer Erosion and contamination Experiment- and were flown in a nadir-facing position for 13 months, which resulted in exposure to omni-directional charged particle radiation, thermal cycling, & low doses of atomic oxygen and direct solar radiation
  • On Orbit photo taken during STS 114 of the zenith facing experiments
  • Samples were analyzed for space-induced embrittlement using a bend test procedure in which the strain necessary to induce surface cracking was determined.I Will soon get back to the test procedure, polymer samples and bend test results for the misse 5 experiment..
  • Degradation of the polymeric material may be due to Space Debris, space radiation, atomic oxygen interaction or thermal cyclingThe main reason for the degradation of spacecraft surfaces is due to the collision with the space junk..their sizes range from 1 to 30 cms.
  • Production of Space Debris: A. Orbital debris production starts at the very beginning of the life of a spacecraft being put into Earth orbit. 1. launch rocket bodies used to boost satellites into orbit are left orbiting the EarthB. During the operational life 1. As the spacecraft is subjected to solar heating, solar radiation, and atomic oxygen material degradation begins to free small particles of paint and multi-layer insulation.C. Towards the end of the life 1. Due to spacecraft object breakup. Object breakup is usually due to collision or explosion on the spacecraft. Explosions occur most frequently when propellant and oxidizer inadvertently mix or when batteries become over-pressurized
  • This is the pic of the Haystack Radaroperated by the MIT Lincoln Laboratory.. It has been collecting orbital debris data for over 10 years on an agreement with the USAF. United states air force. It concludes that there are over ONE HUNDRED THOUSAND debris fragments in orbit with sizes down to 1 cm.
  • Pic shows the New Outer Blanket Layer, or NOBL..prior to the servicing mission. Shows the damage to the HST after Years of exposure to the harsh environment of space..
  • As a result of space radiation, the outer layer of space materials degrade when exposed to leo.An eg is the embrittlement of the TEFLON FLOURINATED ETHYLENE PROPYLENE – FEP outerlayer of the multilayer insulation covering the Hubble Space Telescope
  • Teflonfluorinated ethylene propylene (FEP) (DuPont) is commonly used on exterior spacecraft surfaces for thermal control in the low-Earth orbit environment. Silverized or aluminized Teflon FEP is used for the outer layers of the thermal control blanket because of its high reflectance, low solar absorptance, and high thermal emittance.Teflon FEP is also desirable because, compared with other spacecraft polymers (such as Kapton= polyimide), it has relatively high resistance to atomic oxygen erosion.Because of its comparably low atomic oxygen erosion yield, Teflon FEP has been used unprotected in the space environment.
  • The Hubble Space Telescope (HST) is a space telescope that was carried into orbit by a Space Shuttle in 1990 and still remains in operationIt can take extremely sharp images with almost no background light. Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.
  • The firstexpt was the Forward Technology Solar Cell Expt (FTSCE) : an active expt that tested the performance of 36 current and advanced generation solar cells for use on future spacescraft..Secondly the Second prototype communication Satellite system (PCSat-2) that provided communication system and tested the Amatuer Satellite Service..The passive expt is the expt we’re interested in..
  • PEACE: Polymer Erosion and contamination experiment
  • MISSE 5 was placed in the zenith/nadir position the P6 Trunion Pin Handrail of the ISS during the STS114 mission on Aug 2005And was exposed to leo for 13 months and retreived on September 15 2006 during the STS115 mission
  • It is estimated that polymers received an ionizing radiation dose of ~2.75 krads through 127 micro meter Kapton(another spacecraft polymer – polyimideKapton= outside layer of space suits, pressure sensitive adhesivesKrads=absorbed radiation dose
  • 165+-25 direct Sun hours (~360 earth reflected
  • ), an atomic oxygen influence of `1.8Xo.10^20 atoms/cm2
  • , 6400 thermal cycles..
  • Atomic oxygen erosion: Numerous events can occur when atomic oxygen impacts a surface.. The atomic oxygen may elastically scatter from the surface in a specular manner, it may energy and momentum accomodate to the surface and then be ejected in a diffuse manner, it may attach to the surface and react with other arriving species to form excited nitrogen oxide, which de-excites to cause the glow phenomenon, or the atomic oxygen may chemically react with the surface
  • Thermal blanket materials expt needed the samplesto be thin and flexible.. Samples were taped on to this kapton blanket substrate
  • Samples were analyzed for space induced embrittlemet using a bend test procedure in which a surface strain was applied without adding overallTrensile load..
  • Test was conducted using an apparatus with a semi suspended pliable platform, and a set of mandrels varying in diameter..
  • TOTAL of 23 mandrels were used ranging in diameter from 1.253 to 0.052 cmEach sample was bend tested using successively smaller mandrels ,with the sample being inspected after being bent around each mandrel..This procedure was continued until cracks were visible..or until the sample did not experience any cracking with the smallest mandrel…
  • If no cracks were observed the sample was tested with a smaller sample..and procedure was repeated..to verify test results sampleswere tested more than once..
  • % strain foreach sample was calculated based on the mandrel at which the it initilally cracked and the thickness of the sample..
  • 50.8 is the thicknessPMP= polymethylpentent
  • Close up photos of sample T1 and X2
  • Microscope images obtained before and after bend testing with each mandrel..sample in the fig is PVF also known as Tedlar. MISSE5 Sample ID T-7Thickness 25.4 micrometer. Cracked udner a strain of just 0.38 percentBox shows the cracks developedduring bend testingFig shows typicalMISSE 5 behavior with the formation of very small but visible vertical cracks…next fig shows more extreme behaviour.
  • Sample X2 .this issample X2 PMP, cracked on orbit..this was found to be extremely embrittled and fractured into pieces during bend testingSpace exposure embrittled this polymer to an extend where the sample fell apart upon bend testing with the largest mandrel. 1.25cm diameter.. With a surface strain of0.4 percent
  • Eg of the sample that dint crack during bend testing and hence remained ductile,psamp;e Polyurethane PU MISSE T5
  • 17 of the 37 tested flight samples experienced some degree embrittlement
  • DNC means did not crackSample M11 had scratches prior to bend testing..which may have affected the bend test results..
  • Bright white materialas such as V2, hard to see fine surface cracks..
  • Embrittlement of Polymers in Space

    1. 1. PE1509Geevarghese George Semester 6 PSE
    2. 2. Embrittlement of MISSE 5 PolymersAfter 13 Months of Space Exposure
    3. 3. NASA STI Programhttp://www.sti.nasa.gov/
    4. 4. ObjectiveTo measure the embrittlement of 37 thin film polymers after LEO space exposure
    5. 5. Why?To design durable and stable spacecraft components
    6. 6. Materials International SpaceStation Experiment (MISSE)
    7. 7. MISSE 5• Polymer samples were taken from PEACE and were flown in a nadir-facing position for 13 months• Samples were exposed to omni-directional charged particle radiation, thermal cycling, & low doses of atomic oxygen and direct solar radiation
    8. 8. Pre Flight photograph of the MISSE 5
    9. 9. Experiment Trays mounted on the ISS
    10. 10. Test for Space Induced Embrittlement Bend TestStrain necessary to induce surface cracking
    11. 11. Causes of Degradation• Space Debris• Space Radiation• Atomic Oxygen Interaction• Thermal Cycling
    12. 12. Space DebrisSize <1 to 30 cm
    13. 13. Haystack Radar
    14. 14. Surface of the HST before the HST Servicing mission
    15. 15. Space RadiationIonizing radiation is known to embrittle polymers
    16. 16. Photograph of embrittled and cracked Teflon FEP retrieved from the HST
    17. 17. Picture of HSTThe Hubble Space Telescope
    18. 18. Atomic Oxygen Interaction
    19. 19. Thermal Cycling
    20. 20. MISSE 5 ExperimentsContained two active (FTSCE & PCSat-2) and one passive (TBME) experiments
    21. 21. Passive ExperimentMISSE 5 Thermal Blanket Materials Experiment• Consisted of several Individual experiments to measure the degradation of more than 200 materials in the space environments• 49 PEACE samples were flown as a part of the Experiment
    22. 22. • MISSE 5 was placed in the zenith/nadir position the P6 Trunion Pin Handrail of the International Space Station• And was exposed to LEO for 13 months and retrieved on September 15 2006 during the STS115 mission
    23. 23. Ionizing Radiation~2.75 Krads through 127 micrometer Kapton
    24. 24. Sun Hours 165±25
    25. 25. Atomic Oxygen Influence ~1.8X0.10^20 atoms/cm2
    26. 26. Thermal Cycles 6400
    27. 27. MISSE 5 PEACE Polymers Experiment = Thermal Blanket Materials Experiment •MISSE 5 PEACE polymers experiment consisted of 49, 0.5X1.5in rectangular polymer samples •Majority of the samples were thin and flexible
    28. 28. Primary objective was to determine the Atomic Oxygen Erosion Yield (Ey) of polymers after exposure to space in nadir position
    29. 29. • Thin samples were taped on to a Kapton blanket substrate therefore making determination of Ey based on mass loss difficult• So samples were dusted with fine salt spray particles to provide isolated locations of protectionfrom AOE so that recession depth measurements could be made post flight for Ey determination
    30. 30. Experiment Procedures
    31. 31. Sectioning Bend-Test Samples• A piece measuring 0.5 X 0.2in of each sampled was sectioned for bend testing• Small salt particles were removed from the samples prior to bend testing by: Brushing with a small horse hair water color brush Rinsing with water and then gently drying the sample with pressurized Nitrogen
    32. 32. Bend Test ProcedureStrain necessary to induce surface cracking was determined by bending the samples over mandrels
    33. 33. 23 nos1.253 to 0.052 cm
    34. 34. • Sample was placed with the space exposed face down onto the semi guided apparatus• Mandrel was pushed down onto the sample forcing the material against the pliable surface• Sample was bent in a U shape where the space exposed surface was in tension and the backside was under compression• As the diameter of the mandrel decreases, the tension on the space exposed surface increases because the sample was forced to bend more tightly around the material
    35. 35. The samples where examined before and after bend testing at magnifications of 10x to 13.8xUsing an Olympus SMZ stereo zoom optical microscope outfitted with a Canon digital camera
    36. 36. Depending on the size of the samples 9 to 15Optical microscopy pictures were taken and observed for cracks during the bend test process and were recorded
    37. 37. Strain CalculationsAllows the percent strain E to be calculated based on the thickness of the sample t and the diameter of the mandrel d E = {t/(d+t)} * 100
    38. 38. Results and Discussion
    39. 39. TWOsamples cracked in half while on-orbit • Sample T-1 : PMMA, 50.8 µm • Sample X-2 : PMP, 50.8 µm
    40. 40. 17
    41. 41. These results indicate that many thin film polymers are susceptible to embrittlement in the LEO spaceatmosphere, even after low solar and particle radiation
    42. 42. Therefore even minimal amounts of radiation exposure must not be overlooked when designingspacecraft components based onexpected mechanical properties.

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