Carbon nanotube-reinforced composites dispersion properties

Another method to improve the mechanical properties such as interfacial strength is to add nanosized carbon fiber-reinforced particles into the composite [18-20]. A strong influence of a uniform dispersion of the small-sized fibers or partides on the composite properties of advanced nanocomposites, such as carbon nanotube-reinforced composites was also reported [21-24]. However, few papers mention the enhancing method for improving the interfacial adhesion between fiber and matrix in a natural BF composite. 

CNTs can enhance the thermal properties of CNT-polymer nanocomposites. The reinforcing function is closely associated with the amount and alignment of CNTs in the composites. Well-dispersed and long-term stable carbon nanotubes/ polymer composites own higher modulus and better thermal property as well as better electronic conductivity (Valter et al., 2002 Biercuk et al., 2002). Both SWNT and MWNT can improve the thermal stability and thermal conductivity of polymer, the polymer-CNT composites can be used for fabricating resistant-heat materials. 

El Badawi N, Ramadan AR, Esawi AMK, El-Morsi M (2014) Novel carbon nanotube-cellulose acetate nanocomposite membranes for water filtration applications. Desalination 344 79-85 Esteban EU-B, Matthew JK, Virginia AD (2013) Dispersion and rheology of multiwalled carbon nanotubes in unsaturated polyester resin. Macromolecules 46(4) 1642-1650 Fang L, Xue Y, Lin H, Shuai C (2011) Friction properties of carbon nanotubes reinforced nitrile composites under water lubricated condition. Adv Mater Res 284—286 611-614 Fangming D, John EF, Karen IW (2003) Coagulation method for preparing single-walled carbon nanotube/poly(methyl methacrylate) composites and their modulus, electrical conductivity, and thermal stability. J Pol) Sci Part B Polym Phys 41(24) 3333-3338... 

Poly(vinyl) alcohol (PVA) is a semi-crystalline polymer, which is already widely used for various applications, either under the form of films or fibers. Compared to other polymers, as it is water-soluble at high temperature, it is easy to process from aqueous solutions. Carbon nanotubes can also be dispersed or solubilized in water via different functionalization approaches. It was quite natural for researchers to try to mix carbon nanotubes and PVA to improve the properties of the neat polymer. In this chapter, we will first examine the different methods that have been used to process CNT/PVA composites. The structures and the particular interaction between the polymer and the nanotube surface have been characterized in several works. Then we will consider the composite mechanical properties, which have been extensively investigated in the literature. Despite the number of publications in the field, we will see that a lot of work is still to be done for achieving the most of the exceptional reinforcement potential of carbon nanotubes. 

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. 

Carbon-based polymer nano composites represent an interesting type of advanced materials with structural characteristics that allow them to be applied in a variety of fields. Functionalization of carbon nanomaterials provides homogeneous dispersion and strong interfacial interaction when they are incorporated into polymer matrices. These features confer superior properties to the polymer nanocomposites. This chapter focuses on nanodiamonds, carbon nanotubes and graphene due to their importance as reinforcement fillers in polymer nanocomposites. The most common methods of synthesis and functionalization of these carbon nanomaterials are explained and different techniques of nanocomposite preparation are briefly described. The performance achieved in polymers by the introduction of carbon nanofillers in the mechanical and tribological properties is highlighted, and the hardness and scratching behavior of the nanocomposites are also discussed. 

Improved dispersion of nanoscaled fillers in polymers is expected to lead to better mechanical properties. The question is if by using a nano-modified matrix instead of a laminate with neat polymer as the matrix, in a fiber-reinforced composite can lead to improve delamination resistance. In the case of semicrystalline polymer matrices, the scenario is even more complicated as the microstructure is not only influenced by the processing but also by the presence of nanofillers. The addition of different types of nanoscaled reinforcements such as carbon nanotubes, nanofibers or... 

More recently nanoscale fillers such as clay platelets, silica, nano-calcium carbonate, titanium dioxide, and carbon nanotube nanoparticles have been used extensively to achieve reinforcement, improve barrier properties, flame retardancy and thermal stability, as well as synthesize electrically conductive composites. In contrast to micron-size fillers, the desired effects can be usually achieved through addihon of very small amounts (a few weight percent) of nanofillers [4]. For example, it has been reported that the addition of 5 wt% of nanoclays to a thermoplastic matrix provides the same degree of reinforcement as 20 wt% of talc [5]. The dispersion and/or exfoliahon of nanofillers have been identified as a critical factor in order to reach optimum performance. Techniques such as filler modification and matrix functionalization have been employed to facilitate the breakup of filler agglomerates and to improve their interactions with the polymeric matrix. 

Peddini et al. [9] used oxidized multiwalled carbon nanotubes (MWCNTs) as reinforcement in SBR matrices to improve the rheological properties and thus the elastomer performances in tires. Materials containing 15% MWCNTs proved to have the highest dispersion. In a further study [10], the group assessed the tensile stress-stain behavior of the resulted composites, showing that the stress is reduced with the increase of the nanotube concentration. 

Nanofillers may be nanoclays, carbon nanotubes (single or multiwall) (CNTs), silica, layered double hydroxides (LDHs), metal oxides, etc., offering the promise of a variety of new composites, adhesives, coatings, and sealant materials with specific properties [32-37]. Among the fillers mentioned, nanoclays have attracted most of the academia and industry interest, due to their abrmdance as raw materials and to the fact that their dispersion in polymer matrices has been studied for decades [38]. In fact, there are three major polymer nanocomposites categories in terms of nanofiller type that are expected to compile the global nanocomposites market in 2011 nanoclay-reinforced (24%), metal oxide-reinforced (19%), and CNTs-reinforced (15%) ones [39-41]. 

The discovery of carbon nanostructured materials has inspired a range of potential applications. More specifically, the use of carbon nanotubes in polymer composites has attracted wide attention. Carbon nanotubes have a unique atomic structure, a very high aspect ratio, and extraordinary mechanical properties (strength and flexibility), making them ideal reinforcing compounds. Moreover, carbon nanotubes are susceptible to chemical functionalization, which broaden their applicability. For instance, surface functionalization of carbon nanotubes is an attractive route for increasing their compatibility with polymers in composites, also improving the dispersability in raw materials and the wettability. 

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