1E-161E-151E-141E-131E-121E-111E-101E-091E-081E-071E-061E-051E-04

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

Foam_TopFoam_BottomComposite_TopComposite_Bottom

Surf

ace

Con

duct

ivity

(1/O

hm)

GOALI/Collaborative Research: Fabrication of Ultra-light Multifunctional Nanofoams from Polymer NanocompositesGrant No.: CMMI-0728287NSF 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 AustinCo-PI: Samra Sangari, Boeing Commercial Airplanes, The Boeing Company

Anti-static

Electromagnetic interferenceshielding

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 IIFoamingDesorption

Syringe Pump

Properties Values

Density 1.28 g/ccTensile Strength, Ultimate 114 MPa

Tensile Modulus 3.45 GpaElectrical conductivity 1e-17 S/cm

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

Polymer matrix (PEI)

Factors Values

CNT wt% 0.5 – 3wt% (0.5wt% interval)Saturation pressure 8 MPaSaturation time 24 hoursFoaming temperature 175 CFoaming time 20 seconds

Factors in the experiment

02468

10121416

0 0.5 1 1.5 2 2.5 3

Mas

s Lo

ss P

erce

ntag

e

CNT wt%

Mass loss by ScCO2 after Vacuum Oven treatment

Mass loss by Vacuum Oven treatment

1E-181E-171E-161E-151E-141E-131E-121E-111E-101E-091E-081E-071E-061E-05

-0.5 0 0.5 1 1.5 2 2.5 3 3.5

Volu

me

Con

duct

ivity

(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

10

20

30

40

50

60

0 0.5 1 1.5 2 2.5 3

Relativ

e Den

sity (%

)

CNT wt%

1E-181E-171E-161E-151E-141E-131E-121E-111E-101E-091E-081E-071E-061E-05

-0.5 0 0.5 1 1.5 2 2.5 3 3.5

Volu

me

Con

duct

ivity

(S/C

m)

CNT wt%

CompositesFoams

2.85E-08

1.30E-13

1.88E-12

1.09E-10

1E-171E-161E-151E-141E-131E-121E-111E-101E-091E-081E-071E-06

Unfoamed Foamingcondition-1

Foamingcondition-2

Foamingcondition-3

DC

Con

duct

ivity

(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: 195C, 20 sec in glycerol bath

Scale bars: 1 µm

CNTs

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