Carbon nano tubes dispersability

The above analysis takes the synthesis methods, the performance affected by the dispersion of CNTs, enhanced physical properties and the latest applications of carbon nanotube/polyurethane composites described in literature reports as the reference point. In the interest of brevity, this is not a comprehensive review, however, it goes through numerous research reports and applications which have been learned and described in the recent years. Despite that, there are still many opportunities to synthesize new carbon nano-tube/polyurethane systems and to modify carbon nanotubes with new functional groups. The possibility of producing modern biomedical and shape memory materials in that way makes the challenge of the near future. 

The concept of toughening on the nano scale is the subject for much current research where particles of, for example, clays, carbon fibre and carbon nano-tubes, are being evaluated as tougheners for brittle, often high-temperature epoxy matrices. In the same way as for polymeric additives, the main difficulties being experienced are those of particle exfoliation, in the case of the clays, and dispersion in the case of the carbon particles. 

Qrikasa, H., Inokuma, N., Okubo, S., Kitakami, O., and Kyotani, T. Template synthesis of water-dispersible carbon nano test tubes without any post treatment. Chem. Mater. 18, 2006 1036-1040. 

Brunauer-Emmet-Teller (BET) estimated surface areas [23], For example, from Figure 5.9, graphite felt electrodes show poor volume-normalized ORR current density compared to carbon nanofibers and multiwaUed carbon nanotube (MWCNT)-based electrodes. However, the results also reveal that CNTs and porous carbon tubes exhibit dramaticaUy lower ORR current densities when normalized to B ET surface area, while graphite felt electrodes perform better, perhaps indicative of agglomeration of the carbon tubes, preventing enzyme adsorption over the entire area. Further research on methods to permit dispersion of nano-tubes, while retaining electrical conductivity and adsorption of enzymes oriented for DET, is warranted. 

In a similar approach, it is not the monomer, but a solution of the prefabricated polymer (polyacrylonibile in this case) in DMF that is being used. Herein the SWNTs are very finely dispersed. The product then also contains nano tubes aligned in the fiber s longitudinal direction. Another procedure resembles the method of producing carbon fibers from PAN (Section 1.2.3). Here the composite fibers are carbonized to yield a material of nanotube-reinforced carbon fibers. At a nanotube portion of as little as 3%, it already exhibits markedly improved mechanical properties. 

Nano tubes, in particular SWNTs, are typically held together as bundles, resulting in poor NT dispersion in polymer matrices. Since, due to the relatively smooth graphene Hke surface of NTs, there is a lack of interfacial bonding between polymer matrix and carbon nanotubes, surface modification by chemical means of NTs has been envisaged as a very important factor to overcome this problem and to fadhtate NTs processing and applications [30]. 

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