JEC COMPOSITES MAGAZINE - Issue #56 - April 2010 - 95

consistently obtained in carbon-fibre-reinforced (CFR) composites containing 0.2 to 1 wt% of MWCNTs. It is also important to note that unlike rubber-based impact modifiers, MWCNTs do not strongly impact the Tg of the resins. This can be explained by the fact that 10 wt% of a low-modulus additive (typical loading for rubber additives) is replaced by 1 wt% of a high-modulus additive (MWCNTs). Table 1 illustrates the properties obtained in a CFR composite made of woven T300 (Soficar) carbon fibres.

25 is dispersed in a classical DGEBA epoxy resin (10,000 mPa.s, cured with DDS hardener), percolation occurs at about 0.1 wt% of MWCNTs. This percolation threshold can be further decreased by using resins of lower viscosities. Therefore, a resistivity of 104 Ohm.cm can consistently be obtained by diluting Graphistrength CS1-25 a hundred times in most epoxy resins. This resistivity range is particularly interesting for glass-fibre-reinforced composites or for CFR composites that need transverse conductivity.

Electrical improvements
While mechanical improvements are difficult to predict, electrical conductivity can be tuned very precisely and consistently. Figure 5 shows the variation in volume resistivity as a function of MWCNT loading. This percolation curve is linked to the organization of the MWCNT network within the matrix. Percolation occurs when a

MWCNT functionalization
A lot of work has been done and reported on the functionalization of carbon nanotubes. The purpose is to covalently graft chemical groups on the surface of carbon nanotubes to enhance their affinity to their host matrix and thus improve the performance of composites. However, the benefit-to-cost ratios of these procedures have proved disappointing so far. Although dispersion qualities are often improved, mechanical performance can be decreased due to the fact that carbon nanotubes are frequently broken under the severe conditions of functionalization (usually oxidation in concentrated acids under sonication). Electrical properties are also lowered due to the combination of two factors: i) the disruption of the outer MWCNT wall which is the main conduction pathway, and ii) the addition of chemical groups (typically amines or aliphatic chains) which form an insulating shell around the nanotubes. Non-covalent functionalization, i.e. physical adsorption of compatibilizing agents, does not change the nanotube structures but still leads to the formation of insulating shells. Therefore, all MWCNT concentrates produced by Arkema contain nonfunctionalized MWCNTs that are ideal for electrical performance, while maintaining or even improving mechanical properties and bringing optimum performance-to-cost ratios.
More information: www.arkema.com

Fig. 5: Percolation curve obtained by diluting Graphistrength® CS1-25 in a classical DGEBA epoxy resin cured with DDS hardener. Mixing was done on a Silverson LR4T high shear mixer for 30 min at 5,000 rpm

sufficient number of MWCNTs are connected together, leading to a significant drop in electrical resistivity. When Graphistrength® CS1-

INDEX
See the beginning of the list on page 5
FPC - - - - - - - - - - - - - - - - - - - - - - - - - p. 18 Fraunhofer IPT Aachen - - - - - - - - - - - - p. 71 Groupe Depestele - - - - - - - - - - - - - - - p. 32 Harusmas Agro Sdn - - - - - - - - - - - - - - p. 32 Henkel Corporation - - - - - - - - - - - - - - p. 37 Hexcel - - - - - - - - - - - - - - - - - - - pp. 17, 22 Icolfibra - - - - - - - - - - - - - - - - - - - - - - p. 39 InChem - - - - - - - - - - - - - - - - - - - - - - p. 57 Ingersoll - - - - - - - - - - - - - - - - - - - - - p. 63 Institut fuer Verbundwerkstoffe pp. 33, 65, 75 Invent - - - - - - - - - - - - - - - - - - - - - - - - p. 42 Jacques Ferrier Architects - - - - - - - - - p. 78 Klebchemie m.G. Becker GmbH & Co. - - p. 33 Lineo - - - - - - - - - - - - - - - - - - - - - - - - p. 32 Lingol - - - - - - - - - - - - - - - - - - - - - - - - p. 57 Lomold Pty - - - - - - - - - - - - - - - - - - - - p. 39 LTP - - - - - - - - - - - - - - - - - - - - - - - - - p. 41 Magestic Systems - - - - - - - - - - - - - - - p. 35 Mainz University of Applied Sciences - MBM Maschinenbau Mühldorf Gmbh - Mikrosam - - - - - - - - - - - - - - - - - - - - Mitsubishi Rayon - - - - - - - - - - - - - - - Molded Fiber Glass Companies - - - - - NASA - - - - - - - - - - - - - - - - - - - - - - - Nordson EFD - - - - - - - - - - - - - - - - - - OCV Reinforcement - - - - - - - - - - - - - Oerlikon Saurer - - - - - - - - - - - - - - - - Oxeon - - - - - - - - - - - - - - - - - - - - - - - Peugeot - - - - - - - - - - - - - - - - - - - - - Phoenix Equipment Company - - - - - - - Premium Aerotec - - - - - - - - - - - - - - - Porsche AG - - - - - - - - - - - - - - - - - - - S.A.B.C.A - - - - - - - - - - - - - - - - - - - - Saertex - - - - - - - - - - - - - - - - - - - - - Sala Macchine - - - - - - - - - - - - - - - - - Samsonite Europe - - - - - - - - - - - - - - Sandvik Process Systems - - - - - - - - - p. 42 p. 31 p. 63 p. 17 p. 24 p. 55 p. 48 p. 41 p. 68 p. 18 p. 78 p. 54 p. 10 p. 34 p. 34 p. 41 p. 67 p. 39 p. 67 Selcom Multiaxial Technology - - - - - - - p. 48 SGL Group - - - - - - - - - - - - - - - - - - - - p. 17 Specialty Products - - - - - - - - - - - - - - - p. 57 Stanford University - - - - - - - - - - - - - - - p. 89 Terre de Lin - - - - - - - - - - - - - - - - - - - - p. 9 The Phoenix Equipment Company - - - - - p. 54 Thermwood - - - - - - - - - - - - - - - - - - - - p. 56 Toho Tenax - - - - - - - - - - - - - - - - - - - - p. 17 Toray Soficar - - - - - - - - - - - - - - - - - - - p. 17 TTT The Team Composite - - - - - - - - - - p. 39 University of Delaware - - - - - - - - - - - - p. 56 University of Maine - - - - - - - - - - - - - - - p. 42 US Commercial Service - - - - - - - - - - - - p. 54 Utah/Milken Institute - - - - - - - - - - - - - p. 54 VEM - - - - - - - - - - - - - - - - - - - - - - - - - p. 53 Wabash MPI - - - - - - - - - - - - - - - - - - - p. 55 Wellman Products Grp - - - - - - - - - - - - p. 40 Xperion/CDI - - - - - - - - - - - - - - - - - - - p. 57 Zoltek - - - - - - - - - - - - - - - - - - - - - - - p. 17

No56 April 2010 / jec composites magazine

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http://www.arkema.com
JEC COMPOSITES MAGAZINE - Issue #56 - April 2010

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #56 - April 2010
