Carbon nanotube-filled polymer composites

In this chapter, the development of functional CNT-polymer composites in recent years will be addressed in detail. The focus will be on processing methods for fabricating the superstrong and/or conductive composite materials. In addition, important aspects of the mechanical and electrical behavior of CNT-polymer composites as well as their potential applications will be analyzed. 

Polymer Composites Volume 2, First Edition. Edited by Sabu Thomas, Kuruvilla Joseph, Sant Kumar Malhotra, Koichi Goda, and Meyyarappallil Sadasivan Sreekala. 

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Yang YL, Gupta MC, Dudley KL, Lawrence RW (2005) A Comparative Study of EMI Shielding Properties of Carbon Nanofiber and Multi-Walled Carbon Nanotube Filled Polymer Composites. J. nanosci. nanotechnol. 5 927-931. 

Dalmas, R, et al., 2006. Carbon nanotube-filled polymer composites. Numerical simulation of electrical conductivity in three-dimensional entangled fibrous networks. Acta Mater. 54 (11), 2923-2931. 

In order to better understand the micromechanical behavior of carbon nanotube filled polymers, the load transfer behavior and interfacial shear stress must be quantified. This paper presents preliminary work on an experimental technique for quantifying the relative interfacial shear stress in multi-walled carbon nanotube / polycarbonate composites. The procedure provides a comparison of the aspect ratio of the nanotubes pulled from a fracture surface. In addition, the correlation with pullout angle is discussed. This work showed a decrease in the aspect ratio and thus an increase in interfacial shear as a result of chemical surface modification to multiwall nanotubes. 

N.A., Alexander, M., Vaia, R.A., 2004. Remotely actuated polymer nancxomposites—stress-recovery of carbon-nanotube-filled thermoplastic elastomers. Nat Mater. 3, 115-120. Copyright 2004, Macmillan Publishers Ltd. (B) Reproduced with permission from reference Yu, A., Meiser, F., Cassagneau, T., Caruso, F., 2004. Fabrication of polymer-nanopartide composite inverse opals by a one-step electrochemical co-deposition process. Nano Lett 4, 177-181. Copyright 2004, American Chemical Society. (C) Reproduced with permission from reference Fie, X., Shi, Q., Zhou, X., Wan, C., Jiang,... 

In many composites, conducting fillers (carbon black, carbon nanotubes, or metal nanoparticles) are added to make material conductive. The relationship between composite morphology and electrical conductivity has been studied extensively, especially in the context of carbon black filled polymers [156-162]. It is well known that the dependence of conductivity on the loading of conductive filler, percolation theory there is some threshold filler loading below which there is no conductive pathway through the system and conductivity is zero above the threshold, conductivity grows very rapidly as ... 

Figure 12.5. Volume resistivity against filler loading for SBR composites filled with carbon black (CB Ensaco 250G from Timcal) and MWNTs. [Figure 5A is reprinted from L. Bokobza, M. Rahmani, C. Belin, J.-L. Bruneel, N.-E. El Bounia "Blends of carbon blacks and multwall carbon nanotubes as reinforcing fillers for hydrocarbon rubbers", Journal of Polymer Science Part B Polymer Physics, 46,1939, 2008, permission from John Wiley and Sons].

Therefore, it can be seen from the above expression that is closely related to absorption loss (SE ). SE is also important for porous structures (e.g., foams) and for certain type of filled composites (carbon nanofibers [CNFs]/carbon nanotubes [CNTs]/graphene-filled polymers) or for certain design geometries (e.g., honeycomb lattices) [1,2,9,13,81]. It can be neglected in the case of a shield having thick absorbing elements due... 

For carbon nanotubes, discussed in detail in Chapter 10, conductivity is achieved at lower loadings (by weight) but these materials are difficult to disperse in molten polymers. Methods of surface functionalization and lower cost manufacturing must be developed before carbon nanotubes will find wider use as conductive fillers [52, 53]. As an alternative to nanotubes, Fukushima and Drzal [54] have observed conductivity thresholds of less than 3 vol% in composites containing acid-etched or othervdse functionalized exfoliated graphite. These composites retain or improve upon their mechanical properties compared to other carbon-filled polymers. 

Bayley, G. M. Hedenquist, M. Mallon, P. E., Large Strain and Toughness Enhancement of Poly(dimethylsiloxane) Composite Films Filled with Electros-pun Polyacrylonitrile-graft-Poly(dimethylsiloxane) Fibers and Multi-Walled Carbon Nanotubes. Polymer 2011, 52,4061-4172. 

Thermal conductivity studies have been conducted on a wide range of filled polymers and composites, including carbon fibers [62-68], aluminum powder [65], nitride [66], magnetite, barite, talc, copper, strontium ferrite [67], glass fiber-filled polypropylene and manganese or iron-filled polyaniline, carbon nanotubes [68], and nickel-cobalt-zinc ferrite in natural rubber [70]. 

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