GOALI/Collaborative Research: Fabrication of Ultra-light ......

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  • 1E-16 1E-15 1E-14 1E-13 1E-12 1E-11 1E-10 1E-09 1E-08 1E-07 1E-06 1E-05 1E-04

    -0.5 0 0.5 1 1.5 2 2.5 3 3.5 CNT wt%

    Foam_Top Foam_Bottom Composite_Top Composite_Bottom

    Su rf

    ac e

    C on

    du ct

    iv ity

    (1 /O

    hm )

    GOALI/Collaborative Research: Fabrication of Ultra-light Multifunctional Nanofoams from Polymer Nanocomposites Grant No.: CMMI-0728287 NSF Program: NM/GOALI

    Introduction  High performance polymer nanocomposites

    • Taking advantages of excellent inherent properties of high performance polymer matrices

    • Improved mechanical, thermal, and electrical properties by adding nano-additives in the polymer matrix

     Nanofoams have benefits of foamed materials • Light-weight products • Thermal insulation and sound-proof properties • Higher strength-to-weight ratio

     Combining the benefits of high performance polymer nanocomposites and nanofoams • Light-weight, multifunctional materials with excellent mechanical,

    thermal, and electrical properties for various applications • Possible higher and more effective electromagnetic interference

    shielding property while maintaining inherent excellent mechanical and thermal properties of high performance polymer

    Objectives  To develop an innovative fabrication approach to multifunctional nanofoams from high performance

    polymeric nanocomposites  To study the envisioned multi-functionality of high performance nanocomposite nanofoam materials,

    such as high electrical conductivity and low density with inherent excellent properties of the polymer matrix.

    Conclusions  The PEI/CNT foams showed significantly improved electrical conductivity satisfying the ANSI/ESD

    standard for dissipative materials with reduced density.  It is expected that the PEI/CNT foams can serve as light-weight electronics protection materials under

    high temperature and stress due to its multifunctionality.  The PEI/CNT nanofoams were fabricated with the pore size of under 100 nm. Further characterizations

    are needed to demonstrate the property improvement for nanofoams compared to microfoams.

    Acknowledgements - Graduate students Nick Vaccaro, Jeremy Barker, Emmanuel Cua, and Yongha Kim. - Dr. Edmond Kung at SABIC for providing PEI.

    Results  Solvent extraction effect on volumetric electrical

    conductivity of nanocomposites

    • Residual solvent contents : 12-14% - Weaken mechanical and thermal properties • No notable effect of residual solvent on the electrical conductivity

     Volume conductivity of composites and foams

    • Volume conductivity satisfies the ANSI/ESD(2008) for dissipative materials • ANSI/ESD(2008) criteria for dissipative materials: 1E-11 to 1E-4 (S)

     Surface conductivity of composites and foams

    PI: Wei Li, Department of Mechanical Engineering, University of Texas at Austin Co-PI: Samra Sangari, Boeing Commercial Airplanes, The Boeing Company

    Anti-static

    Electromagnetic interference shielding

    Lightning strike mitigation

    Experimental  The high pressure solid state foaming process

     Sample preparation • Functionalized MWCNTs from Cheap Tubes, Inc. • Ultem PEI 1010P provided by SABIC Innovative

    plastics. • PEI/CNT composites preparation

    − Solvent casting (Solvent: DCM)

    Temperature Controller

    CO2 Tank Pressure Vessel

    Stage I Saturation

    Stage II FoamingDesorption

    Syringe Pump

    Properties Values

    Density 1.28 g/cc Tensile Strength, Ultimate 114 MPa

    Tensile Modulus 3.45 Gpa Electrical conductivity 1e-17 S/cm

    Dielectric Constant 3.15 Glass Transition Tg 216 °C Stable Service Temperature ~170°C

     Polymer matrix (PEI)

    Factors Values

    CNT wt% 0.5 – 3wt% (0.5wt% interval) Saturation pressure 8 MPa Saturation time 24 hours Foaming temperature 175 C Foaming time 20 seconds

     Factors in the experiment

    0 2 4 6 8

    10 12 14 16

    0 0.5 1 1.5 2 2.5 3

    M as

    s Lo

    ss P

    er ce

    nt ag

    e

    CNT wt%

    Mass loss by ScCO2 after Vacuum Oven treatment

    Mass loss by Vacuum Oven treatment

    1E-18 1E-17 1E-16 1E-15 1E-14 1E-13 1E-12 1E-11 1E-10 1E-09 1E-08 1E-07 1E-06 1E-05

    -0.5 0 0.5 1 1.5 2 2.5 3 3.5

    Vo lu

    m e

    C on

    du ct

    iv ity

    (S /C

    m )

    CNT wt%

    Before VO

    After VO

    After ScCO2

     Relative density of foams

    • Significant density reduction was achieved by foaming

     SEMs

    • Dispersed CNTs were found throughout the polymer matrix for both unfoamed and foamed samples

    • Pore sizes were around 1 micrometer • Bonding between CNTs and the matrix needs to be improved to

    maximize the additive effect (Future research)

    0

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    0 0.5 1 1.5 2 2.5 3

    Re la tiv

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    si ty  (%

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    CNT wt%

    1E-18 1E-17 1E-16 1E-15 1E-14 1E-13 1E-12 1E-11 1E-10 1E-09 1E-08 1E-07 1E-06 1E-05

    -0.5 0 0.5 1 1.5 2 2.5 3 3.5

    Vo lu

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    (S /C

    m )

    CNT wt%

    Composites Foams

    2.85E-08

    1.30E-13

    1.88E-12

    1.09E-10

    1E-17 1E-16 1E-15 1E-14 1E-13 1E-12 1E-11 1E-10 1E-09 1E-08 1E-07 1E-06

    Unfoamed Foaming condition-1

    Foaming condition-2

    Foaming condition-3

    D C

    C on

    du ct

    iv ity

    (S /c

    m )

    0 wt% Pure PEI

    (195 , 2)  (195, 30)  (175, 30) (Temp(C), Time(sec)) 

    • Surface conductivity for foams satisfies the ANSI/ESD(2008) for dissipative materials

    • Conductivities of bottom surfaces were higher than that of top surfaces

    Data from previous study with CNF

    Unfoamed Foamed

    0wt% CNT

    1.5wt% CNT

    3wt% CNT

    Scale bars: 2 µm

    • Saturation conditions: 8MPa, 24hours • Foaming conditions: 195C, 20 sec in glycerol bath

    Scale bars: 1 µm

    CNTs

    Nanofoamed PEI/CNT(0.5wt%) nanocomposite (Pore size:~100nm)