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Improvements to the Synthesis of Polyimide Aerogels · PDF file 2013-04-10 · Improvements to the Synthesis of Polyimide Aerogels Cross-linked polyimide aerogels are viable approach

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  • Improvements to the Synthesis of Polyimide Aerogels

    Cross-linked polyimide aerogels are viable approach to higher temperature, flexible insulation for inflatable decelerators. Results indicate that the all- polyimide aerogels are as strong or stronger than polymer reinforced silica aerogels at the same density. Currently, examining use of carbon nanofiber and clay nanoparticles to improve performance. Flexible, polyimide aerogels have potential utility in other applications such as space suits, habitats, shelter applications, etc. where low dusting is desired

    https://ntrs.nasa.gov/search.jsp?R=20110011361 2020-03-08T13:32:12+00:00Z

    meitelki Typewritten Text .

  • National Aeronautics and Space Administration

    Improvements to the synthesis of polyimide aerogelsp y g

    Mary Ann B. Meador, Baochau N. Nguyen, Haiquan Guo Stephanie Vivod Zuhui He ErickaHaiquan Guo, Stephanie Vivod, Zuhui He, Ericka

    Malow and Rebecca Silva

    NASA Glenn Research Center Cleveland, OH 44135

    [email protected]

    www.nasa.gov 1

  • National Aeronautics and Space Administration

    What are aerogels?

    Sol Gel Aerogel • Highly porous solids made by drying a wet gel

    without shrinking • Pore sizes extremely small (typically 10-40

    g

    Pore sizes extremely small (typically 10-40 nm)—makes for very good insulation

    • 2-4 times better insulator than fiberglass under ambient pressure 10-15 times better in light

    Typical monolithic silica aerogels

    ambient pressure, 10 15 times better in light vacuum

    • Invented in 1930’s by Prof. Samuel Kistler of the College of the Pacific

    www.nasa.gov 2

    the College of the Pacific

  • National Aeronautics and Space Administration

    Examples of current commercial aerogel productsproducts• Cabot

    – Pellets, composite – Oil and gas pipeline insulation – Cryo-insulation – Day-lighting applications

    • Aspen Aerogels – Flexible blanket insulation – Oil and gas pipeline – Construction materials

    Aerospace apparel– Aerospace, apparel • Nanopore

    – Vacuum insulation panels Shipping containers– Shipping containers

    – Refrigeration – Apparel

    www.nasa.gov 3

  • National Aeronautics and Space Administration

    Monolithic silica aerogels out-perform particulate forms as insulation

    …but are extremely fragile and

    forms as insulation

    fragile and moisture sensitive

    and limited to a few

    Doug Smith, Aerogel Conference, 2007

    …and limited to a few exotic applications

    www.nasa.gov 4

    Cosmic dust collector – Stardust Program Insulation on rovers

  • National Aeronautics and Space Administration

    Potential applications for durable aerogels in aeronautics and space explorationaeronautics and space exploration

    Cryotank Insulation Air revitalizationFan engine containment (Ballistic protection)

    Sandwich structures

    Ultra-lightweight, multifunctional structures for habitats, rovers

    Insulation for EVA suitsHeat shielding

    www.nasa.gov 5

    Insulation for EVA suits, habitats and rovers

    Heat shielding Propellant tanks Inflatable aerodynamic

    decelerators

  • National Aeronautics and Space Administration

    Durable aerogels by reinforcing with polymersg y g p y

    Native Cross-linked

    • Polymer reinforcement doubles the density

    • Results in two order of• Results in two order of magnitude increase in strength

    • Reduces surface area by y only 30-50%

    • Leventis, Meador, Johnston, Fabrizio, and Ilhan, US Patent No. 7,732,496; June 8, 2010

    www.nasa.gov 6

    7,73 , 96; June 8, • Jason P. Randall, Mary Ann B. Meador, and Sadhan C. Jana,

    ACS Appl. Mater. Interfaces, 2011, 3 (3), pp 613–626

  • National Aeronautics and Space Administration

    Typical Aerogel Cross-linking Process Silanes

    in solvent H2O/solvent

    /catalyst

    Wash (water, l h l )

    15 min

    SOL GEL alcohols) Soak in

    monomer bath

    Crosslinked Aerogel

    heat

    SCF d i Wash

    ( SCF drying (CO2)

    (excess polymer)

    www.nasa.gov 7

    Cross-linked

  • National Aeronautics and Space Administration

    Process/property optimization of di-isocyanate cross linked aerogelscross-linked aerogels

    Empirical models… Low density...

    10000

    1000

    e

    0 01 0.1

    1

    10

    100

    1000

    M od

    ul us

    , M P

    a

    1

    10

    100

    N o.

    h ex

    am et

    hy le

    ne re

    pe at

    u ni

    ts

    sed for predictions of optima

    0.01

    0.4 0.8

    1.2 1.6

    2.0

    4 6

    8 10

    12

    Tota l sila

    ne, m ol/l

    H 2 O, mol/l

    1

    0.4 0.8

    1.2 1.6

    2.0

    4 6

    8 10

    12 14

    Tota l sila

    ne, m ol/l

    H 2 O, mol/l

    0 washes 2 washes 4 washes

    …used for predictions of optima

    …to high density… MP a 10

    100 Measured Predicted

    t u ni

    ts

    20

    25

    30 Measured Predicted

    g y and everything

    in-between

    29 30 31 32 33 34 35 36 37

    M od

    ul us

    ,

    0.01

    0.1

    1

    29 30 31 32 33 34 3 36 3

    H D

    I r ep

    ea t

    0

    5

    10

    15

    www.nasa.gov 8

    Meador et al, Chemistry of Materials, 2007, 19, 2247-2260 Run

    29 30 31 32 33 34 35 36 37 Run

    29 30 31 32 33 34 35 36 37

  • National Aeronautics and Space Administration

    Reduced bonding in silica backbone leads to excellent elastic recovery over modulus range of 0 01 to 100 MPaelastic recovery over modulus range of 0.01 to 100 MPa

    6

    8

    Modulus = 89 MPa Density = 0 403 g/cm3Pore structure

    St re

    ss , M

    P a

    2

    4

    6

    Test 1 Test 2

    Density 0.403 g/cmPore structure influenced by

    bonding

    • Use of MTMS instead of TMOS gives Strain

    0.00 0.05 0.10 0.15 0.20 0.25 0

    • Use of MTMS instead of TMOS gives 25 % reduction in Si-O-Si bonding

    • Almost all length is recovered after two compressions to 25% MP

    a

    0.06

    0.08

    0.10

    Modulus = 0.12 MPa Density = 0.093 g/cm3

    p • Polymer cross-linking provides

    increased modulus/maximum stress at break

    S tre

    ss ,

    0 00

    0.02

    0.04 Test 1

    Test 2

    www.nasa.gov 9

    Strain

    0.00 0.05 0.10 0.15 0.20 0.25 0.00

    Nguyen et al, ACS Applied Materials and Interfaces, 2010, 2, 1430–1443

  • National Aeronautics and Space Administration

    One pot process streamlines aerogel fabricationfabrication

    Four Washes

    SCEne P

    ot • Eliminating diffusion Shortens process

    Sol with epoxy Gel with epoxy Epoxy reinforced gel

    Epoxy reinforced aerogel

    SCE

    Two

    M ul

    O n – Shortens process

    – Cross-linking more efficient

    – Aerogels are more uniform

    SolGel

    Monomer diffusion

    Two washes

    ltistep • Properties are the same as multistep when 15 mol % APTES used

    400

    • Higher APTES leads to much higher density, lower surface area 100

    200

    300

    400

    1.0Su rfa

    ce a

    re a,

    m 2 /

    g

    – Diffusion not a factor – Amount of polymer cross-

    linking much higher

    0 1.2

    1.4

    1.6

    5 10 15 20 25 30 35 40

    S

    To tal

    Si , m

    ol/ l

    BTMSH, mol %

    APTES = 15 mol % APTES = 30 mol %

    www.nasa.gov 10

    Meador et al, ACS Applied Materials and Interfaces, 2010, 2, 2162-2168

    APTES = 45 mol %

  • National Aeronautics and Space Administration

    www.nasa.gov 11

  • National Aeronautics and Space Administration

    Improved insulation for inflatable p o ed su a o o a ab e re-entry vehicles

    B li i l ti i A A l• Baseline insulation is Aspen Aerogels Pyrogel 3350

    • Needs to be more flexible foldable lessNeeds to be more flexible, foldable, less dusty, thermally stable

    • Target: thin film aerogels with nanofiber reinforcement – Silica aerogels with PDMS flexible linking groups – Silica aerogels reinforced with polyimideg p y – Cross-linked polyimide aerogels – Manufacture into thin film form

    Electrospun fibers in film for added

    www.nasa.gov

    – Electrospun fibers in film for added durability/flexibility

    12

  • National Aeronautics and Space Administration

    Collaboration with University of Akron—thin film aerogels reinforced with electrospun nanofiberaerogels reinforced with electrospun nanofiber

    • Sol cast into thin film • Electrospun fibers of PDMS/PU

    Solution A

    Solution B

    Sol with desired

    viscosity

    mix Film cast Nanofiber

    Electrospinning

    deposited into film • Flexible nanofibers bridge

    cracks/hold structure together

    Solution B y

    Gelation

    Aging

    Solvent Exc.Reinforced Silic