Carbon nanotube polymer composites a review of recent developments
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Carbon Nanotube Polymer Composites: A Review of Recent Developments. Rodney Andrews & Matthew Weisenberger University of Kentucky Center for Applied Energy Research. Nanotube composite materials are getting stronger, but…. …not there yet…. Nanotube Composite Materials.

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Carbon Nanotube Polymer Composites: A Review of Recent Developments

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Carbon nanotube polymer composites a review of recent developments

Carbon Nanotube Polymer Composites: A Review of Recent Developments

Rodney Andrews & Matthew Weisenberger

University of Kentucky

Center for Applied Energy Research


Carbon nanotube polymer composites a review of recent developments

Nanotube composite materials are getting stronger, but…

…not there yet…


Nanotube composite materials

Nanotube Composite Materials

  • Engineering MWNT composite materials

    • Lighter, stronger, tougher materials

      • Lighter automobiles with improved safety

      • Composite armor for aircraft, ships and tanks

    • Conductive polymers and coatings

      • Antistatic or EMI shielding coatings

      • Improved process economics for coatings, paints

    • Thermally conductive polymers

      • Waste heat management or heat piping

  • Multifunctional materials


High strength fibers

High Strength Fibers

  • To achieve a high strength nanotube fiber:

    • High strength nanotubes (> 100 GPa)

    • Good stress transfer from matrix to nanotube

      • Or, nanotube to nanotube bonding

    • High loadings of nanotubes

    • Alignment of nanotubes (< 5° off-axis)

    • Perfect fibers

      • Each defect is a separate failure site


Carbon nanotube polymer composites a review of recent developments

Issues at the Interface

  • Interfacial region, or interaction zone, can have different properties than the bulk polymer:

    • chain mobility,

    • entanglement density,

    • crosslink density

    • geometrical conformation

  • Unique reinforcement mechanism

    • diameter is of the same size scale as the radius of gyration

    • can lead to different modes of interactions with the polymer.

    • possible wrapping of polymer chains around carbon


Mwnt matrix interface

MWNT/Matrix Interface

  • The volume of matrix that can be affected by the nanotube surface is significantly higher than that for traditional composites due to the high specific surface area.

  • 30nm diameter nanotubes have about 150 times more surface area than 5 µm fibers for the same filler volume fraction

Ding, W., et al., Direct observation of polymer sheathing in carbon nanotube-polycarbonate composites. Nano Letters, 2003. 3(11): p. 1593-1597.


Interphase region

Interphase Region

  • Nanotube effecting crystallization of PP

  • Sandler et al, J MacroMol Science B, B42(3&4), pp 479-488,2003


Two approaches for surface modification of mwnts

Two Approaches for Surface Modification of MWNTS

  • Non-covalent attachment of molecules

    • van der Waals forces: polymer chain wrapping

    • Alters the MWNT surface to be compatible with the bulk polymer

    • Advantage: perfect structure of MWNT is unaltered

      • mechanical properties will not be reduced.

    • Disadvantage: forces between wrapping molecule / MWNT maybe weak

      • the efficiency of the load transfer might be low.

  • Covalent bonding of functional groups to walls and caps

    • Advantage: May improve the efficiency of load transfer

      • Specific to a given system – crosslinking possibilities

    • Disadvantage: might introduce defects on the walls of the MWNT

      • These defects will lower the strength of the reinforcing component.


Polymer wrapping

Polymer Wrapping

  • Polycarbonate wrapping of MWNT (Ruoff group)

Ding, W., et al., Direct observation of polymer sheathing in carbon nanotube-polycarbonatecomposites. Nano Letters, 2003. 3(11): p. 1593-1597.


Shi et al polymer wrapping

Shi et al - Polymer Wrapping

  • Activation/etching of MWNT surface

  • Plasma deposition of 2-7 nm polystyrene

  • Improved dispersion

  • Increased tensile strength and modulus

  • Clearly defined interfacial adhesion layer

  • Shi, D., et al., Plasma coating of carbon nanofibers for enhanced dispersion and interfacial bonding in polymer composites. Applied Physics Letters, 2003. 83(25): p. 5301-5303.


Carbon nanotube polymer composites a review of recent developments

Co-valent Functionalization

Epoxide terminated molecule and

carboxylated nanotubes

Schadler, RPIAndrews, UK


Velasco santos et al

Velasco-Santos et. Al.

  • Functionalization and in situ polymerization of PMMA

  • COOH and COO- functionalities

  • in situ polymerization with methyl methacrylate

  • increase in mechanical properties for both nanotube composites compared to neat polymer

  • improvements in strength and modulus of the functionalized nanotube composite compared to unfunctionalized nanotubes

  • The authors conclude that “functionalization, in combination with in situ polymerization , is an excellent method for producing truly synergetic composite materials with carbon nanotubes”

  • Velasco-Santos, C., et al., Improvement of Thermal and Mechanical Properties of Carbon Nanotube Compositesthrough Chemical Functionalization. Chemistry of Materials, 2003. 15: p. 4470-4475.


In situ polymerization of pan

In Situ Polymerization of PAN

  • Acrylate-functionalized MWNT which have been carboxilated

  • Free-radical polymerization of acrylonitrile in which MWNTs are dispersed

  • Hope to covalentely incorporate MWNTs functionalized with acrylic groups


Strong matrix fiber interaction

Strong Matrix Fiber Interaction

  • SEM images of fracture surfaces indicate excellent interaction with PAN matrix, note ‘balling up’ of polymer bound to the MWNT surface. This is a result of elastic recoil of this polymer sheath as the fiber is fractured and these mispMWNTs are pulled out.


20 wt mwnt carbon fiber

20 wt% MWNT/Carbon Fiber


Baughman group

Baughman Group

  • poly(vinyl alcohol) fibers

    • containing 60 wt.% SWNTs

  • tensile strength of 1.8GPa

  • 80GPa modulus for pre-strained fibers

  • High toughness

    • energies-to-break of 570 J/g

    • greater than dragline spider silk and Kevlar

  • Dalton, A.B., et al., Super-tough carbon-nanotube fibres. NATURE, 2003. 423: p. 703


Kearns et al pp swnt fibers

Kearns et al – PP/SWNT Fibers

  • SWNT were dispersed into polypropylene

    • via solution processing with dispersion via ultrasonic energy

    • melt spinning into filaments

  • 40% increase in tensile strength at 1wt.% SWNT addition, to 1.03 GPa.

  • At higher loadings (1.5 and 2 wt%), fiber spinning became more difficult

    • reductions in tensile properties

  • “NTs may act as crystallite seeds”

    • changes in fiber morphology, spinning behavior

    • attributable to polymer crystal structure.

  • Kearns, J.C. and R.L. Shambaugh, Polypropylene Fibers Reinforced with Carbon Nanotubes. Journal of Applied Polymer Science, 2002. 86: p. 2079-2084


Kumar et al

Kumar et al

  • SWNT/Polymer Fibers

    • PMMA

    • PP

    • PAN

  • Fabricated fibers with 1 to 10 wt% NT

    • Increases in modulus (100%+)

    • Increases in toughness

    • Increase in compressive strength

    • Decrease in elongation to break

    • Decreasing tensile strength


Kumar pbo swnt fibers

Kumar – PBO/SWNT Fibers

  • high purity SWNT (99% purity)

  • PBO poly(phenylene benzobisoxazole)

  • 10 wt% SWNT

  • 20% increase in tensile modulus

  • 60 % increase in tensile strength (~3.5 GPa)

    • PBO is already a high strength fiber

  • 40% increase in elongation to break

  • Kumar, S., et al., Fibers from polypropylene/nano carbon fiber composites. Polymer, 2002. 43: p. 1701-1703.

  • Kumar, S., et al., Synthesis, Structure, and Properties of PBO/SWNT Composites. Macromolecules, 2002. 35: p. 9039-9043.

  • Sreekumar, T.V., et al., Polyacrylonitrile Single-Walled Carbon Nanotube Composite Fibers. Advanced Materials, 2004. 16(1): p. 58-61.


Electrospun fibers

Electrospun Fibers

  • (latest Science article)

  • Leaders in Field

    • Frank Ko – Drexel University

    • ESpin Technologies (TN)

  • Ko has done extensive work for DoD

    • Reasonable strengths, but poor transfer fibril to fibril

    • Not a contiguous graphite structure


Conclusions

Conclusions

  • Nanotubes are > 150 GPa in strength.

    • Strain-to-break of 10 to 20%

    • Should allow 100 GPa composites

  • Challenges still exist

    • Stress transfer / straining the tubes

    • Controlling the interface

    • Eliminating defects at high alignment

  • Work is progressing among many groups


Acknowledgements

University of Kentucky

Center for Applied Energy Research

Acknowledgements

  • Financial Support of the Kentucky Science and Engineering Foundation under grant KSEF-296-RDE-003 for “Ultrahigh Strength Carbon Nanotube Composite Fibers”


Questions

Questions???


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