Carbon nanotubes dispersion mechanism

Mallakpour S, Zadehnazari A. One-pot synthesis of glucose functionalized multi-walled carbon nanotubes dispersion in hydrox-ylated poly(amide-imide) composites and their thermo-mechanical properties. Polymer 2013 54(23) 6329-38. 

Mathur R B, Singh B P, Dhami T L, Kalra Y, Lai N, Rao R and Rao A M (2010), Influence of carbon nanotube dispersion on the mechanical properties of phenolic resin composites , Polym Compos, 31, 321—327. 

Barroso-Bujans et al. [60] prepared nanocomposites of carbon nanotubes and sul-fonated ethylene-propylene-norbomene terpolymer and compared the mechanical properties of carbon nanotubes and carbon black ethylene-propylene-norborene composites. They also evaluated the effect of carbon nanotube dispersion on the mechanical, thermal, and electrical behavior. 

S. Bal, "Influence of dispersion states of carbon nanotubes on mechanical and electrical properties of epoxy nanocomposites," Journal of Scientific and Industrial Research, vol. 66, pp. 752-756, 2007. 

Nanocarbon structures such as fullerenes, carbon nanotubes and graphene, are characterized by their weak interphase interaction with host matrices (polymer, ceramic, metals) when fabricating composites [99,100]. In addition to their characteristic high surface area and high chemical inertness, this fact turns these carbon nanostructures into materials that are very difficult to disperse in a given matrix. However, uniform dispersion and improved nanotube/matrix interactions are necessary to increase the mechanical, physical and chemical properties as well as biocompatibility of the composites [101,102]. 

T. E. Chang, A. Kisliuk, S. M. Rhodes, W. J. Brittain, A.P. Sokolov, Conductivity and mechanical properties of well-dispersed single-wall carbon nanotube/polystyrene composite, Polymer, vol. 47, pp. 7740-7746, 2 0 06. 

CNT randomly dispersed composites Many soft and rigid composites of carbon nanotubes have been reported [17]. The first carbon-nanotube-modified electrode was made from a carbon-nanotube paste using bromoform as an organic binder (though other binders are currently used for the paste formation, i.e. mineral oil) [105]. In this first application, the electrochemistry of dopamine was proved and a reversible behavior was found to occur at low potentials with rates of electron transfer much faster than those observed for graphite electrodes. Carbon-nanotube paste electrodes share the advantages of the classical carbon paste electrode (CPE) such as the feasibility to incorporate different substances, low background current, chemical inertness and an easy renewal nature [106,107]. The added value with CNTs comes from the enhancement of the electron-transfer reactions due to the already discussed mechanisms. 

As authors supposed from the generally accepted concepts of mechanisms of carbon nanotube growth, the dispersed nickel sputtered must catalyze the growth of these nanotubes. The source for carbon should be carbon from the hydrocarbon that transforms into the vaporous state in the arc zone. It has been supposed to prepare single-wall nanotubes on the nickel particles 1-10 nm in size and the layer of nanotubes up to 1 pm thick on the larger nickel particles. 

Carbon nanotubes (CNTs) have shown exceptional stiffness, strength and remarkable thermal and electrical properties, which make them ideal candidates for the development of multifunctional material systems [22], Nowadays, CNTs are dispersed within polymer in order to improve their mechanical and electrical properties [23], Therefore, reinforcement of PB films by CNTs might be a strategy for manufacturing mechanically robust ion-... 

We review the research on preparation, morphology, especially physical properties and applications of polyurethane (PU)/carbon nanotube (CNT) nanocomposites. First, we provide a brief introduction about the preparation of PU/CNT nanocomposites. Then, the functionalization and the dispersion morphology of CNTs as well as the structures of the nanocomposites are also introduced. After that, we discuss in detail the effects of carbon nanotubes on the physical properties (including mechanical, thermal, electrical, rheological and other properties) of PU/CNT nanocomposites. The potential applications of these nanocomposites are also addressed. Finally, the challenges and the research that needs to be done in the future for achieving high-performance polyurethane/carbon nanotube nanocomposites are prospected. 

The gap between the predictions and experimental results arises from imperfect dispersion of carbon nanotubes and poor load transfer from the matrix to the nanotubes. Even modest nanotube agglomeration impacts the diameter and length distributions of the nanofillers and overall is likely to decrease the aspect ratio. In addition, nanotube agglomeration reduces the modulus of the nanofillers relative to that of isolated nanotubes because there are only weak dispersive forces between the nanotubes. Schadler et al. (71) and Ajayan et al. (72) concluded from Raman spectra that slippage occurs between the shells of MWNTs and within SWNT ropes and may limit stress transfer in nanotube/polymer composites. Thus, good dispersion of CNTs and strong interfacial interactions between CNTs and PU chains contribute to the dramatic improvement of the mechanical properties of the... 

Jin et al. (65) used poly(vinylidene fluoride) (PVDF) as a compatibilizer to assist dispersion of CNTs in PMMA. Multi-walled carbon nanotubes were first coated with PVDF and then melt-blended with PMMA. Poly(vinylidene fluoride) served as an adhesive to improve wetting of CNTs by PMMA and to increase the interfacial adhesion resulting in improved mechanical properties of MWCNT-PMMA composites. 

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. 

This paper represents an overview of investigations carried out in carbon nanotube / elastomeric composites with an emphasis on the factors that control their properties. Carbon nanotubes have clearly demonstrated their capability as electrical conductive fillers in nanocomposites and this property has already been commercially exploited in the fabrication of electronic devices. The filler network provides electrical conduction pathways above the percolation threshold. The percolation threshold is reduced when a good dispersion is achieved. Significant increases in stiffness are observed. The enhancement of mechanical properties is much more significant than that imparted by spherical carbon black or silica particles present in the same matrix at a same filler loading, thus highlighting the effect of the high aspect ratio of the nanotubes. 

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