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Nanocomposites: mixing
CNTs into polymers
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Outline
1.Introduction
2. Composites of multiwalled carbon nanotubes (MWNT) withpolycarbonate (PC) produced by masterbatch dilution technique
Electrical resistivity
Dispersion and alignment
Influence of processing parameters on electrical resistivity3. Composites of MWNT and SWNT with PC produced by direct
incorporation
Percolation of different commercial MWNT in PC
Percolation of SWNT in PC
Stress-strain behaviour
4. Summary
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Electrical conductivity
Improvement of mechanical properties, especiallystrength
Enhancement of thermal stability Enhancement of thermal conductivity
Improvement of fire retardancy
Enhancement of oxidation stability
Effects at low CNT contents because of the very highaspect ratio
Benefits of CNTs to polymers
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How to introduce CNTs into
polymers
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Melt mixing of CNT with
thermoplastic polymers
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Preparation of the PC-MWNT
composites Masterbatch technology: polycarbonate(PC) +PC based masterbatch (15 wt% MWNT) masterbatch (Hyperion Catalysis International, Inc,
Cambridge, USA) diluted with PC Iupilon E2000(PC1), PC Lexan 121 (PC2) or PC as used for themasterbatch (PC3)
Haakeco-rotating, intermeshing twin screw extruderwith one kilogramm mixtures
DACA Micro Compounder, conical twin screwextruder (4.5 cm3capacity)
Brabender PL-19 single screw extruder
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Characterization of the
masterbatch (PC + 15 wt% MWNT)
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Dispersion in PC-MWNT
composites
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Alignment in PC-MWNT
composites
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Comparison for different set of PC
masterbatch dilution
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Detection of percolation and influence of processing
conditions investigated by dielectric spectroscopy
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Direct incorporation of different
kinds of commercial MWNT into PC
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Comparison of direct incorporation of CNT,
masterbatch dilution, and CB addition
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Direct incorporationof SWNT1 into PC
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Direct incorporation of SWNT1 into PC
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Direct incorporation of SWNT1 into PC
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Direct incorporationof SWNT2 into PC
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Direct incorporation of SWNT2 into PC
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Summary
Melt mixing is a powerful method to disperse CNT into polymers
Masterbatch dilution technique (based on a PC masterbatch)
percolation in the range of 1.0 wt% MWNT
suitable processing conditions can shift percolation to lower values(0.5wt%)
effects of mixing eq
uipment and PC viscosity on percolation are small Direct incorporation method
percolation strongly depends on the kind of CNT, production method(resulting in different sizes, purity and defect levels), and thepurifying/modification steps
for commercial MWNT percolation occurs between 1.0 and 3.0 wt% andis lower at lower MWNT diameters and higher purity
HipCO-SWNT (CNI) percolation between 0.30 and 0.35 wt% stress-strain behavior of the composites: modulus and stress are
enhanced, elongation at break reduced especially above percolationconcentration
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Graphenepolymer composite
Graphite oxide was prepared by the Hummers method from SP-1 graphite(Bay Carbon), and dried for a week over phosphorus pentoxide in a vacuumdesiccator. Dried graphite oxide (50 mg) was suspended in anhydrous DMF(5 ml, Dow-Grubbs solvent system), treated with phenyl isocyanate (2 mmol,Sigma-Aldrich) for 24 h, and recovered by filtration through a sintered glassfunnel (50 ml, medium porosity). Stable dispersions of the resulting phenyl
isocyanate-treated graphite oxide materials were prepared by ultrasonicexfoliation (Fisher Scientific FS60, 150 W, 1 h) in DMF (1 mg ml-1).Polystyrene (Scientific Polymer Products, approximate Mw = 280 kD, PDI =3.0) was added to these dispersions and dissolved with stirring (Fig. 1d, left).Reduction of the dispersed material (Fig. 1d, right) was carried out withdimethylhydrazine (0.1 ml in 10 ml of DMF, Sigma-Aldrich) at 80C for24 h. Upon completion, the coagulation of the polymer composites wasaccomplished by adding the DMF solutions dropwise into a large volume of
vigorously stirred methanol (10:1 with respect to the volume of DMF used).The coagulated composite powder (Fig. 1e) was isolated via filtration;washed with methanol (200 ml); dried at 130C under vacuum for 10 h toremove residual solvent, anti-solvent, and moisture; crushed into a finepowder with a mortar and pestle, and then pressed (Fig. 1f) in a hydraulichot press (Model 0230C-X1, PHI-Tulip) at 18 kN with a temperature of210C.
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Process flow of graphene
polymer composite fabrication a, SEM and digital image (inset) of natural graphite. b, A typical
AFM non-contact-mode image of graphite oxide sheets depositedonto a mica substrate from an aqueous dispersion (inset) withsuperimposed cross-section measurements taken along the red lineindicating a sheet thickness of 1 nm. c, AFM image of phenylisocyanate-treated graphite oxide sheets on mica and profile plotshowing the 1 nm thickness. d, Suspension of phenyl isocyanate-treated graphite oxide (1 mg ml-1) and dissolved polystyrene in DMFbefore (left) and after (right) reduction by N,N-dimethylhydrazine. e,Composite powder as obtained after coagulation in methanol. f, Hot-pressed composite (0.12 vol.% of graphene) and pure polystyrene ofthe same 0.4-mm thickness and processed in the same way. g, Low(top row) and high (bottom row) magnification SEM images obtainedfrom a fracture surface of composite samples of 0.48 vol.% (left) and2.4 vol.% (right) graphene in polystyrene.
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Advantages of Nanosized Additions
The Nanocomposites 2000 conference has revealed clearly the
property advantages that nanomaterial additives can provide in
comparison to both their conventional filler counterparts and base
polymer. Properties which have been shown to undergo substantial
improvements inclu
de: Mechanical properties e.g. strength, modulus and dimensional stability Decreased permeability to gases, water and hydrocarbons
Thermal stability and heat distortion temperature
Flame retardancy and reduced smoke emissions
Chemical resistance
Surface appearance
Electrical conductivity
Optical clarity in comparison to conventionally filled polymers
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Disadvantages of Nanosized
Additions To date one of the few disadvantages associated with
nanoparticle incorporation has concerned toughness andimpact performance. Some of the data presented hassuggested that nanoclay modification of polymers such
as polyamides, could reduce impact performance.Clearly this is an issue which would requireconsideration for applications where impact loadingevents are likely. In addition, further research will benecessary to, for example, develop a better
understanding of formulation/structure/propertyrelationships, better routes to platelet exfoliation anddispersion etc.
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Examples of Mechanical Property
gains due to Nanoparticle Additions Data provided by Hartmut Fischer of TNO in the Netherlands
relating to polyamide montmorillonite nanocomposites indicatestensile strength improvements of approximately 40 and 20% attemperatures of 23C and 120C respectively and modulusimprovements of 70% and a very impressive 220% at the sametemperatures. In addition Heat Distortion Temperature was shown toincrease from 65C for the unmodified polyamide to 152C for thenanoclay-modified material, all the above being achieved with just a5% loading of montmorillonite clay. Similar mechanical propertyimprovements were presented for polymethyl methacrylate clayhybrids.
Further data provided by Akkepeddi ofHoneywell relating to
polyamide-6 polymers confirms these property trends. In addition,the further benefits of short/long glass fibre incorporation, togetherwith nanoclay incorporation, are clearly revealed.
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Area of Applications
Such mechanical property improvements have resultedin major interest in nanocomposite materials innumerous automotive and general/industrial applications.These include potential forutilization as mirror housings
on various vehicle types, door handles, engine coversand intake manifolds and timing belt covers. Moregeneral applications currently being considered includeusage as impellers and blades for vacuum cleaners,power tool housings, mower hoods and covers for
portable electronic equipment such as mobile phones,pagers etc.
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Gas Barrier
The gaseous barrier property improvement that can result fromincorporation of relatively small quantities of nanoclay materials isshown to be substantial. Data provided from various sources indicatesoxygen transmission rates for polyamide-organoclay compositeswhich are usually less than half that of the unmodified polymer.Further data reveals the extent to which both the amount of clay
incorporated in the polymer, and the aspect ratio of the fillercontributes to overall barrier performance. In particular, aspect ratio isshown to have a major effect, with high ratios (and hence tendenciestowards filler incorporation at the nano-level) quite dramaticallyenhancing gaseous barrier properties. Such excellent barriercharacteristics have resulted in considerable interest in nanoclaycomposites in food packaging applications, both flexible and rigid.Specific examples include packaging for processed meats, cheese,
confectionery, cereals and boil-in-the-bag foods, also extrusion-coating applications in association with paperboard for fruit juice anddairy products, together with co-extrusion processes for themanufacture of beer and carbonated drinks bottles. The use ofnanocomposite formulations would be expected to enhanceconsiderably the shelf life of many types of food.
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Fuel Tanks
The ability of nanoclay incorporation to reduce solventtransmission through polymers such as polyamides hasbeen demonstrated. Data provided by De Bievre andNakamura of UBE Industries reveals significant
reductions in fuel transmission through polyamide6/66polymers by incorporation of a nanoclay filler. As a result,considerable interest is now being shown in thesematerials as both fuel tank and fuel line components forcars. Of further interest for this type of application, the
reduced fuel transmission characteristics areaccompanied by significant material cost reductions.
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Films
The presence of filler incorporation at nano-levels has also beenshown to have significant effects on the transparency and hazecharacteristics of films. In comparison to conventionally filledpolymers, nanoclay incorporation has been shown to significantlyenhance transparency and reduce haze. With polyamide basedcomposites, this effect has been shown to be due to modifications inthe crystallisation behaviour brought about by the nanoclay particles;spherilitic domain dimensions being considerably smaller. Similarly,nano-modified polymers have been shown, when employed to coatpolymeric transparency materials, to enhance both toughness andhardness of these materials without interfering with lighttransmission characteristics. An ability to resist high velocity impactcombined with substantially improved abrasion resistance wasdemonstrated by Haghighat of Triton Systems.
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Environmental Protection
Water laden atmospheres have long been regarded as one of themost damaging environments which polymeric materials canencounter. Thus an ability to minimize the extent to which water isabsorbed can be a major advantage. Data provided by Beall fromMissouri Baptist College indicates the significant extent to whichnanoclay incorporation can reduce the extent of water absorption in apolymer. Similar effects have been observed by van Es of DSM withpolyamide based nanocomposites. In addition, van Es noted asignificant effect of nanoclay aspect ratio on water diffusioncharacteristics in a polyimide nanocomposite. Specifically, increasingaspect ratio was found to diminish substantially the amount of waterabsorbed, thus indicating the beneficial effects likely from nanoparticleincorporation in comparison to conventional microparticle loading.Hydrophobic enhancement would clearly promote both improvednanocomposite properties and diminish the extent to which waterwould be transmitted through to an underlying substrate. Thus,applications in which contact with water or moist environments is likelycould clearly benefit from materials incorporating nanoclay particles.
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Preparation and Characterization of
Novel Polymer/Silicate Nanocomposites
Five categories cover the majority of composites
synthesized with more recent techniques being
modifications or combinations from this list.
Type I: Organic polymer embedded in aninorganic matrix without covalent bonding
between the components.
Type II: Organic polymer embedded in an
inorganic matrix with sites of covalent bonding
between the components.
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Preparation and Characterization of
Novel Polymer/Silicate Nanocomposites
Type III: Co-formed interpenetrating networks of
inorganic and organic polymers without covalent
bonds between phases.
Type IV: Co-formed interpenetrating networks ofinorganic and organic polymers with covalent
bonds between phases.
Type V: Non-shrinking simultaneous
polymerization of inorganic and organic
polymers.
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Preparation and Characterization of
Novel Polymer/Silicate Nanocomposites
The great majority of nanocomposites
incorporate silica from tetraethoxysilane
(TEOS). The formation of the inorganic
component involves two steps, hydrolysis
and condensation as seen in Scheme 1.
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Polymers considered: PEO, PEO/PPO,
PVAc, PVA, PAN, MEEP
A general synthesis for a base, acid, or salt catalyzed polyphosphazene,polyethylene oxide (PEO), and polyethylene oxide/polypropylene oxide(PPO/PEO) block nanocomposite is as follows: 300 mg of polymer isdissolved into 10 mL of a 50/50 by volume tetrahydrofuran (THF)/ethanolmixed solvent in a capped vial. To this solution is added TEOS (336 mg). Acatalyst is then introduced as an aqueous solution (150 l) and the mixture
is capped and sonicated at 50o
C for 30 minutes. The sol
ution is aged fromhours to days depending upon the catalyst used in a sealed vial and poured
into a Teflon mold and loosely covered at room temperature. Thenanocomposite self assembles as the volatile solvent slowly escapes duringthe condensation process.
The synthesis of polyvinyl acetate (PVAc)/silicate nanocomposites requiresa different approach from the other nanocomposites. PVAc (300 mg) isdissolved into an 50/50 by volume acetic acid/methanol (10 mL) mixed
solvent in a capped vial. To this solution is added TEOS (373 mg). Thesolution is then sonicated for 5 minutes in a sealed vial at room temperatureand poured into a Teflon mould and loosely covered at room temperature.The nanocomposite self assembles during the curing process, whichtypically lasts up to 24 hours. Additional heating at 100C for 30 minutesaids in removing lingering acetic acid from the nanocomposite.
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Novel Rubber Nanocomposites with
Adaptable Mechanical Properties
Silica particles have become more important in tire applicationssince the introduction of the Green Tire by Michelin. As a filler,silica has greater reinforcing power, such as improving tear strength,abrasion resistance, age resistance and adhesion properties thancarbon black [6-8]. However, due to the strong inter-particlehydrogen bonds between hydroxyl groups, the agglomeration nature
of silica is generally believed to be responsible for the significantPayne effect which brings about considerable rolling resistance fortire applications. In order to reduce the filler-filler interaction and/orto enhance the mechanical properties of silica filled composites,researchers have been working for many years on differentstrategies to improve silica-rubber interaction and, in turn, to reducethe rolling resistance. Among these strategies, chemicalmodifications of rubbers by attaching functional groups interactingwith silica [9-22] and surface treatments of silica by reducing surfacepolarity with different silane coupling agents [22-36] are the mostpopular techniques.
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Novel Rubber Nanocomposites with
Adaptable Mechanical Properties
However, these techniques admittedly have quite a few drawbacks.For the former technique, the chemical modification reaction ofrubber was usually not applicable to commercial production and itsdegree of modification was usually very low [9,11,14,18,22].Additionally, the chemical modification was limited to rubber chainends [12,17,20], meaning that the final silica composite was
unsatisfactory in terms of reducing silica agglomeration. For thelatter, the used coupling agents are expensive and it could possiblylower the crosslinking density by reacting with the chemicalingredients for vulcanization. This technique would lead to loweroverall cure rates [34,35], and at the same time it degraded themechanical performance of such silica filled material for tireapplications. In summary, due to these flaws none of the methodsmentioned above could simultaneously ensure both the ability inreducing the silica agglomeration and improving the materialperformance.
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References
[1] J. C. Brosse et al., J. Appl. Polym. Sci., 78, 1461 (2000).
[2] A. F. Halasa et al., Science and Technology of Rubber, 2nd Ed.,Academic Press, 1994.
[3] D. Derouet, P. Phinyocheep, J. C. Brosse and G. Boccaccio, Eur. Polym. J.,
26(12), 1301 (1990).
[4] K. Chino, M. Ashiura, Macromolecules, 34, 9201 (2001).
[5] F. Ferrero, M. Panetti and G. B. Saracco, La Chimica e LIndustria, 66, 3
(1984).[6] P. Dreyfuss, J. P. Kennedy,Anal. Chem., 47, 771 (1975).
[7] A. Brydon, Ph.D. thesis, University of Aberdeen, 1972.
[8] J. M. Stellmann, A. E. Woodward, J. Polym. Sci., A2, 52 (1971).
[9] J. Malhorta et al., Polymer, 30, 467 (1989).
[10] D. Zuchowska, Polymer, 21, 514 (1980).
[11] A. Brydon et al., Makromol. Chem., 178, 1739 (1977).[12] J. March, Advanced Organic Chemistry, 4th Ed., Wiley, 1992.
[13] R. C. Larock, Comprehensive Organic Transformations, 2nd Ed., Wiley,
1999.
[14] BMBF project Supramolekular strukturierte Elastomerkomposite mit
adpativer Energiedissipation, 2003.
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[15] K. Yurekli et al., J. Polym. Sci. Part B. Polym. Phys., 39 256 (2000).
[16] H. Pawlowski and J. Dick, Rubber World, 6, 35 (1992).
[17] F. W. Maine, B. E. Riseborough and J. E. Theberge, Polymer structures
and properties, SPE RETEC, Toronto, 1976.
[18] B. Freund, W. Niedermeier, Kautsch. Gummi Kunsts., 51, 444 (1998).[19] E. Guth and O. Gold, Phys. Rev., 53, 322 (1938).
[20] H. M. Smallwood, J. Appl. Phys., 15, 758 (1944).
[21] J. H. Davis, Plastics and Polymer, 39, 137 (1971).
[22] J. Frhlich and H. D. Luginsland, Rubber World, 4, 28 (2001).
[23] J. D. Ferry, Viscoelastic Properties of Polymers, 3rd ed., Wiley, 1980.
[24] G. M. Bartenev, Structure and Relaxation Properties of Elastomers,Khimiya, Moscow, 1979.
[25] G. M. Bartenev, Doklady Akad. Nauk USSR, 300, 1154 (1988).
[26] G. M. Bartenev, Vysokomol. Soed., A25, 1191 (1983).
[27] D. F. Twiss, J.Chem. Soc., 44, 1067 (1925).
[28] B. Meissner, Rubber Chem. Technol., 68, 297 (1995).
[29] C. C. McCabe and N. Mller, Trans. Soc. Rheol., 5, 329 (1961).[30] J. L. White and J. W. Crowder, J. Appl. Polym. Sci., 18, 1013 (1974).
[31] S. N. Maiti and P. K. Mahapatro, Polym. Compos., 9, 291 (1988).
[32] G. I. Taylor, Proc. Rheo. Soc. London Ser. A, 146, 501 (1934).
[33] N. Mills, J. Appl. Polym. Sci., 15, 2791 (1975).
[34] F. A. Morrison, Understanding Rheology, Oxford University Press, 2001.
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[35] Q. Zheng et al., J. Appl. Polym. Sci., 86, 3166 (2002).
[36] D. Miao et al., Nihon Reoroji Gakkaishi, 31(5), 305 (2003).
[37] Q. Zheng et al., Polymer, 42, 5743 (2001).
[38] S. Vieweg et al., J. Appl. Polym. Sci., 73, 495 (1999).[39] V. Arrighi, I. J. McEwen, H. Qian and M. B. S. Prieto, Polymer, 44,
6259
[40] G. Tsagaropoulos and A. Eisenberg, Macromolecules, 28, 396
(1995).
[41] G. Tsagaropoulos and A. Eisenberg, Macromolecules, 28, 6067
(1995).[42] S. Yano, T. Furukawa, M. Kodomari and K. Kurita, Kobunshi
Rondunshu, 53, 218 (1996).
[43] Y. I. Tien and K. H. Wei, J. Appl. Polym. Sci., 86, 1741 (2002).
[44] Z. S. Petrovic and W. Zhang, Mater. Sci. Forum, 352, 171 (2000).
[45] N. D. Alberola and P. Mele, Polymer Composites, 17, 751 (1996).
[46] A. Yim, R. S. Chahal and L. E. St. Pierre, J. Colloid. Interface Sci., 43,583 (1973).
[47] C. J. T. Landry, B. K. Coltrain, M. R. Landry, J. J. Fitzgerald and V. K.
Long, Macromolecules, 26, 3702 (1993).
[48] M. Takayanagi, S. Uemura and S. Minami, J. Polym. Sci., C5, 113
(1968).