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(12) United States Patent (io) Patent No.: US 9,550,870 B2
Parr et al. (45) Date of Patent: Jan. 24, 2017
(54) METALLIZED NANOTUBE POLYMER (58) Field of Classification Search
COMPOSITE (MNPC)A ND METHODS FOR None
MAKING SAME See application file for complete search history.
(75) Inventors: Cheol Park, Yorktown, VA (US); (56) References Cited
Joycelyn S. Harrison, Hampton, VA
(US); Negin Nazem, Blacksburg, VA U.S. PATENT DOCUMENTS
(US); Larry Taylor, Christiansburg, VA
2003/0158323 Al * 8/2003 Connell ................. B82Y 10/00
(US); Jin Ho Kang, Newport News,
524/495
VA (US); Jae-Woo Kim, Newport
2004/0143043 Al * 7/2004 Gencer et al. ................ 524/105
News, VA (US); Godfrey Sauti,
(Continued)
Hampton, VA (US); Peter T. Lillehei,
Yorktown, VA (US); Sharon E.
Lowther, Hampton, VA (US) OTHER PUBLICATIONS
Ma et al(Preparation and Electromagnetic Interference Shielding
(73) Assignee: The United States of America as
Characteristics of Novel Carbon-Nanotube/Siloxane/Poly-(urea
represented by the Administrator of
urethane) Nanocomposites, J Polymer Sci, Part B: Polymer Phys,
the National Aeronautics and Space
Administration, Washington, DC (US) 43, pp. 345-358, 2005).*
(*) Notice: Subject to any disclaimer, the term of this Primary Examiner Melvin C Mayes
patent is extended or adjusted under 35 Assistant Examiner Michael Forrest
U.S.C. 154(b) by 603 days. (74) Attorney, Agent, or Firm Jennifer L. Riley; Linda
B. Blackburn; Robin W. Edwards
(21) Appl. No.: 12/313,945
(57) ABSTRACT
(22) Filed: Nov. 26, 2008
A novel method to develop highly conductive functional
materials which can effectively shield various electromag-
(65) Prior Publication Data
netic effects (EMEs) and harmful radiations. Metallized
US 2011/0068291 Al Mar. 24, 2011 nanotube polymer composites (MNPC) are composed of a
lightweight polymer matrix, superstrong nanotubes (NT),
Related U.S. Application Data
and functional nanoparticle inclusions. MNPC is prepared
(60) Provisional application No. 61/004,520, filed on Nov. by supercritical fluid infusion of various metal precursors
28, 2007. (Au, Pt, Fe, and Ni salts), incorporated simultaneously or
sequentially, into a solid NT-polymer composite followed by
(51) Int. Cl. thermal reduction. The infused metal precursor tends to
C08J 7/02 (2006.01) diffuse toward the nanotube surface preferentially as well as
B29C 70/88 (2006.01) the surfaces of the NT-polymer matrix, and is reduced to
(Continued) form nanometer-scale metal particles or metal coatings. The
(52) U.S. Cl. conductivity of the MNPC increases with the metallization,
CPC ................ C08J 7/02 (2013.01); B29C 70/882 which provides better shielding capabilities against various
(2013.01); C08J 3/203 (2013.01); C08J 7/06 EMEs and radiations by reflecting and absorbing EM waves
(2013.01); more efficiently. Furthermore, the supercritical fluid infusion
(Continued) (Continued)
c
?G'">. sip
Fly
3e`c.~ cerc
u,44., S K-.N3;P; 4g-':..r..>..CN"FiPI
US 9,550,870 B2
Page 2
process aids to improve the toughness oft he composite films
significantly regardless of the existence of metal.
18 Claims, 6 Drawing Sheets
(51) Int. Cl.
C08J 3/20 (2006.01)
C08J 7/06 (2006.01)
B29K 105/16 (2006.01)
B82Y 30/00 (2011.01)
(52) U.S. Cl.
CPC .......... B29K 2105/167 (2013.01); B82Y 30/00
(2013.01); C08J 2379/08 (2013.01); Y02P
20/544 (2015.11)
(56) References Cited
U.S. PATENT DOCUMENTS
2006/0194928 Al * 8/2006 Charpentier et al....... 525/333.7
2007/0265379 Al * 11/2007 Chen et at. ................... 524/404
2008/0220244 Al * 9/2008 Wai et at. ..................... 428/328
2009/0068241 Al * 3/2009 Britz et at. .................... 424/409
* cited by examiner
U.S. Patent Jan. 24, 2017 Sheet 1 of 6 US 9,550,870 B2
Ag salt
201.s.,
After cure
70tjf.> Aa salt
After cur
70% Aq salt
B e cure
eff.3
-V%
g WCNTIPI ,fig-,10% WrwNT,,PI
U.S. Patent Jan. 24, 2017 Sheet 2 of 6 US 9,550,870 B2
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e
U.S. Patent Jan. 24, 2017 Sheet 3 of 6 US 9,550,870 B2
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U.R. Patent Jan 24 2017 Sheet 4 of US 9,330,870 G2
KQ% SWC \T Samples
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Process g Conditions
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U.R. Patent Jan 24 2017 Sheet 5 of US 9,330,870 G2
dla ,SW-NT::.; NAO
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U.S. Patent Jan. 24, 2017 Sheet 6 of 6 US 9,550,870 B2
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US 9,550,870 B2
2
METALLIZED NANOTUBE POLYMER mer composites require very high conducting filler loadings
COMPOSITE (MNPC)A ND METHODS FOR to reach the level of conductivity for EME shielding, which
MAKING SAME often inevitably lead to reductions in strength and toughness
as well as weight penalties.
CROSS REFERENCE TO RELATED 5 Future aerospace vehicles require structural airframe
APPLICATION materials with tailorable properties to manage the weight,
temperature, structural, radiation, and electromagnetic chal-
The present application claims priority from U.S. Provi- lenges associated with high-speed, high-altitude flights.
sional Application Ser. No. 61/004,520, filed Nov. 28, 2007. Although a number of lightweight materials such as nano-
10 structured polymers, aerogel, honeycomb, metallic foam,
STATEMENT REGARDING FEDERALLY and lattice block have been proposed to reduce weight of
SPONSORED RESEARCH OR DEVELOPMENT aerospace vehicles, lack of thermal stability and mechanical
durability primarily limits their use for airframe structure
The U.S. Government has a paid-up license in this inven- and propulsion systems. Adding non-metallic lightweight
tion and the right in limited circumstances to require the 15 materials in the airframe structure for weight reduction may
patent owner to license others on reasonable terms as cause new challenges such as a series of electromagnetic
provided for by the terms of Cooperative Agreement No. effects (EME) (lightning strike, Electromagnetic interfer-
NCC-1-02043 awarded by the National Aeronautics and ence) and high altitude radiations. Therefore, highly con-
Space Administration. ductive and multifunctional lightweight composite materials
20 are required to protect aerospace vehicles from various EME
BACKGROUND OF THE INVENTION and radiations. Currently, no materials can achieve this level
of conductivity and functionality to protect the vehicles from
1. Field of the Invention EME and radiations.
The present invention relates to materials for effective The essential concept in this work is to develop novel
shielding against non-ionizing and ionizing radiation, such 25 Metallized Nanotube Polymer Composites (MNPC), which
as electromagnetic effects, interference, or neutrons, and, are composed of lightweight polymer matrix, superstrong
more particularly to lightweight, flexible materials with nanotubes, and functional nanoparticle inclusions.
sufficiently high conductivity and magnetic properties for An object of the present invention is to provide light-
effective electromagnetic effects shielding. weight, flexible materials with sufficiently high conductivity
2. Description of Related Art 30 and magnetic properties for effective EME shielding.
To prevent damage from non-ionizing and ionizing radia- An object of the present invention is to provide impreg-
tion, such as electromagnetic effects, interference, or neu- nated metal preferentially deposited on the nanotube sur-
tron electromagnetic effects (EME) such as lightning strike faces inside of the composite, which can improve the
damage and electromagnetic interference on composite air- conductivity of the nanotube networks.
craft vehicles, highly conductive materials are required to 35 An object of the present invention is to provide an
protect the interior electronics, cockpits, and passenger environmentally benign process, requiring no toxic chemical
cabins. Metallic materials such as metal layer coatings or solvents or reducing agents for incorporating metal particles
metal meshes are often used to shield the airframes effec- in this invention and leaving no residual solvents behind.
tively from the EMEs, however, weight reduction may not An object of the present invention is to provide a method
be maintained with these heavy metal structures and the 40 for producing lightweight EME shielding which is economi-
nature of open mesh structure may not protect some local- cally beneficial by recycling COz fluid on a large scale.
ized lightning attachment effectively. On the other hand, Finally, it is an object of the present invention to accom-
lightweight polymeric materials with conventional conduc- plish the foregoing objectives in a simple and cost effective
tive inclusions may not provide sufficient conductivity manner.
required for shielding EMEs without sacrificing the 45
mechanical properties. Metallization or metal coating can be SUMMARY OF THE INVENTION
applied directly to the inclusions such as nanotubes (NT),
prior to forming the composite. However, thorough disper- The present invention addresses these needs by providing
sion of the heavy metallized nanotubes in a polymer resin is a composite shielding material for protecting against elec-
a big challenge to accomplish. 50 tromagnetic effects or interference which is formed from a
The prior art discloses no known lightweight polymeric nanotube polymer composite with functional nanoparticles
composite materials for achieving sufficient shielding effects incorporated into the nanotube polymer composite. The
against EMEs for aerospace or electronic applications. Prior functional nanoparticles are preferably incorporated into the
work generally utilized heavy metal layers or meshes by nanotube polymer composite by means of supercritical fluid
covering the entire airframe. Metallic foams, conductive 55 infusion. In the preferred embodiment, metal particles are
polymers, and conventional polymer composites with con- deposited on top of dispersed nanotube percolation networks
ductive inclusions have been employed to protect airframes of the nanotube polymer composites preferably by means of
from EMEs as well, but the required level of shielding effect supercritical fluid infusion or in situ polymerization. Alter-
was not achieved. natively metal layers may be deposited on top of dispersed
Metallic layers or coatings may provide effective shield- 6o nanotube percolation networks of the nanotube polymer
ing capabilities; however, high weight penalties of using composites preferably by means of supercritical fluid infu-
metallic materials limit their applications. Metallic foams do sion. The manufacturing process includes the steps of pre-
not provide robust mechanical integrity to use as structural paring a nanotube polymer composite and incorporating
applications and the level of the conductivity may not be functional nanoparticles into the nanotube polymer compos-
sufficient for the EME shielding. The conductive polymers 65 ite. The functional nanoparticles are incorporated into the
tend to lose their conductivity at elevated temperatures nanotube polymer composite preferably by means of super-
(>100° C.) by dedoping or dehydration. Conventional poly- critical fluid infusion or in situ polymerization. In the
US 9,550,870 B2
3 4
preferred embodiment, metal particles are deposited on top FIG. ifs hows a high resolution scanning electron micro-
of dispersed nanotube percolation networks of the nanotube graph( HRSEM)o fAg/10 wt% SWCNT/(3-CNAO at a high
polymer composites preferably by means of supercritical accelerating voltage prepared by 70% metallization solution
fluid infusion or in situ polymerization. Alternatively metal before curing;
layers may be deposited on top of dispersed nanotube 5 FIG. 2a shows a scanning probe micrograph of Ag/10 wt
percolation networks of the nanotube polymer composites % SWCNT/(3-CNAO prepared by 20% metallization solu-
preferably by means of supercritical fluid infusion or in situ tion with a topographic atomic force microscopy (AFM)
polymerization. image using tapping mode;
MNPC can provide lightweight, flexible materials with FIG. 2b shows scanning probe micrograph of Ag/10 wt%
sufficiently high conductivity and magnetic properties for 10 SWCNT/(3-CNAO prepared by 20% metallization solution
effective EME shielding. An impregnated metal is prefer- with a tunneling AFM image using TUNA mode;
entially deposited on the nanotube surfaces inside of a FIGS. 3a-d show scanning transmission electron mircro-
composite, which increases the conductivity of the nanotube graph (STEM) micrographs of a microtomed Ag-MNPC
networks. The MNPC process is an environmentally benign 15 (0.1% SWCNT)t aken at specific locations from the surface
process, and no toxic chemical solvents or reducing agents without SWCNT;
are required to incorporate metal particles in this invention; FIGS. 3e-h show STEM micrographs of a microtomed
no residual solvents are left behind in the product in this Ag-MNPC (0.1% SWCNT)t aken at specific locations from
method. The MNPC method is economically beneficial by the surface with SWCNT;
recycling CO2 fluid on a large scale. The supercritical fluid 20 FIG. 4 is a graph showing the effects of metallization on
(SCF)i mpregnation process rapidly incorporates metal par- the low frequency conductivity of Ag-MNPC samples con-
ticles inside of a composite because CO2 fluid has higher taining 10% SWCNT;
diffusivity than conventional fluids. Through this process, FIG. 5 is a graph of stress-strain curves of tensile tests for
metal impregnation can be achieved deep inside of the film 0.1% SWCNT/(3-CNAO composite (control): 0.1%
as well as on the surfaces. The impregnation depth is 25 SWCNT/(3-CNAO composite processed by SCF without
determined by the SCF impregnation conditions such as the metal infusion (no metal infused), and Ag/0.1% SWCNT/
metal precursor concentration, temperature, pressure, and R-CNAO composites prepared by 50%( 50% silver additive)
time. Nano-sized metals (less than 10 mu, typically 2-5 nm and 70% (70% silver additive) metallization solutions
in diameter) can be impregnated inside as well as outside of respectively;
the nanotube composites. The SCF infusion process 30 FIG. 6a shows an HRSEM micrograph of MNPC with Pt
improves the toughness of the nanotube composites and at 70% precursor solution with the 10% SWCNT-polyimide
allows infusion into complex shape samples including composite;
shaded areas. The MNPC properties are tailorable depend- FIG. 6b shows an HRSEM micrograph of MNPC with Ni
ing on the selection of polymer types, nanotube types and 35 at 70% precursor solution with the 10% SWCNT-polyimide
contents, metal precursor types and contents, SCF types and composite; and
infusion conditions. Various metals can be readily incorpo- FIG. 6c shows an HRSEM micrograph of MNPC with Fe
rated into the NT-polymer composites by the SCF infusion at 70% precursor solution with the 10% SWCNT-polyimide
process. composite.
40
BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENT
A more complete description of the subject matter of the
present invention and the advantages thereof, can be The following detailed description is of the best presently
achieved by the reference to the following detailed descrip- 45 contemplated mode of carrying out the invention. This
tion by which reference is made to the accompanying description is not to be taken in a limiting sense, but is made
drawings in which: merely for the purpose of illustrating general principles of
FIG. la shows a high resolution scanning electron micro- embodiments of the invention.
graph( HRSEM)o f Ag/1 wt % SWCNT/(3-CNAO at a high First, uniformly dispersed nanotube polymer composites
accelerating voltage prepared by 20% metallization solu- 50 are prepared and then additional functional nanoparticles are
tion; incorporated into the nanotube( NT)p olymer composites by
FIG. lb shows a high resolution scanning electron micro-
the supercritical fluid (SCF) infusion method. Additionally
graph( HRSEM) of Ag/1 wt % SWCNT/PCNAO at a high
incorporated metal particles or layers deposit preferentially
accelerating voltage prepared by 70% metallization solu-
on top oft he dispersed nanotube percolation networks oft he
tion; 55 NT polymer composites using the SCF infusion to improve
FIG. lc shows a high resolution scanning electron micro-
the shielding effects against EMEs. A high resolution scan-
graph( HRSEM)o f Ag/1 wt % SWCNT/(3-CNAO at a high
ning electron micrograph (HRSEM) of a typical MNPC is
accelerating voltage prepared by 70% metallization solution
shown in FIG. 1. Nanotubes (Single wall carbon nanotubes
before curing;
FIG. ld shows a high resolution scanning electron micro- 60 (SWCNT) used in FIG. 1) appear as flexible curvy fibrils
graph( HRSEM)o fAg/10 wt% SWCNT/(3-CNAO at a high and the SCF infused nano-sized metal particles are shown as
accelerating voltage prepared by 20% metallization solution bright round spots in FIG. 1.
after curing; Metallized Nanotube Polymer Composite (MNPC) is
FIG. le shows a high resolution scanning electron micro- primarily composed of
graph( HRSEM)o fAg/10 wt% SWCNT/(3-CNAO at a high 65 1. lightweight, high temperature, high performance poly-
accelerating voltage prepared by 70% metallization solution mer matrix,
after curing; 2. highly strong, stiff reinforcing nanotubes, and
