Multiwalled MWCNT-polymer composites

At the same time, Peddini et al. described the preparation of nanocomposites from styrene-butadiene mbber (SBR) and multiwall carbon nanotubes (MWCNT). MWCNT are important nanostructures due to the exceptionally high modulus and aspect ratios there has been much interest in using them as reinforcing agents for polymer composites. Styrene-butadiene rubber (SBR), commonly used as a tread stock for tires, is employed here as the matrix for creation of a masterbatch with oxidized MWCNT (12.3-15 wt%). These materials do not show a high level of electrical conductivity as might be expected from a percolation concept, signifying excellent tube dispersion and formation of a bound rubber layer on the discrete MWCNT [126]. 

Fiber-reinforced polymer composites can contain short, discontinuous fibers (usually in thermoplastics see Fig. 1.14) or long, continuous fibers in thermoset resins. Fibers can vary from the usual glass fibers with thicknesses of some tens of micrometers up to nanofibers or carbon nanotubes (single-waiied or multiwalled, SWCNT or MWCNT) about 10 nm thick. The properties of fiber-reinforced composites depend on thickness, length, and volume content of the fibers, as well as on adhesion (interfacial strength) and matrix properties. 

There are other fiber-like structures, such as carbon nanotubes (single-walled, SWCNT, and multiwalled, MWCNT) and different types of whiskers, which are used as reinforcing structures in polymer composites. These composites are discussed in Section 6.3 ( Nanocomposites ). 

Another important electroanalytieal application of modified electrodes is DNA detection [34-40]. Zhang et al. [39] produced an electrochemical DNA sensor based on silver nanoparticles/poly(trans-3-(3-pyridyl) aciylic acid) (PPAA)/multiwalled carbon nanotubes with carboxyl groups (MWCNTs-COOH) modified glassy carbon electrode (GCE). The polymer film was electropolymerized onto MWCNTs-COOH modified electrode by cyclic voltammetry, and then silver nanoparticles were electrodeposited on the surface of PPAA/MWCNTs-COOH composite film. The novel electrochemical detection method of DNA hybridization-based modified electrode has been developed with high sensitivity and selectivity. Furthermore the results of the experiment indicated that the DNA sensor is of excellent reusability. 

Very recently [92] again applying the concept of microfibrillar composites, microfibrils of polyfhutylene terephthalate) loaded with 5 wt% multiwalled carbon nanombes (MWCNTs) were prepared by extraction of PP from drawn PP/ (PBT-CNT) blends and shaped into single polymer composites. The SPCs show superior mechanical performance with up to 300-600 % improvement in modulus and tensile strength as compared to neat isotropic PBT [92]. 

Among all nanocomposites of ECPs, the most common is nanocomposites of ECPs with CNTs. The properties of CNTs are quite amenable to making porous ECP composites, and as they are also extremely strong, the reinforcement of the composite is also remarkable. For example, pellet electrodes were made from chemically synthesised PPy-multiwalled carbon nanombe (MWCNT) nanocomposites by just pressing without any polymer binder and this composite had a specific capacitance of 495 F g [69]. The strength of the nanocomposite provided by MWCNT is evident because the pellet composite electrodes pressed at 500 kg cm retained their porous internal stmcture to allow fast ion difihision and migration as a result of the strength contributed by the MWCNTs [69]. 

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