Fabrication of CNT Polymer Composites

Supplier (Product) CNT type Purity (% nanotubes) Diameter (nm) Length (pm) Density (g/cc) Price  

Bayer MaterialScience (Baytubes ) Catalytic - MWNT 95-99 % 13-16 nm 1- 10 140-230 kg/m3 bulk 560-700 /kg 

Thomas Swan (Elicarb) High Purity MWNT 70-90% 10-12 nm tens of microns 32-80 /g 

The use of surfactants and the chemical functionalization of CNT surfaces have also been investigated in efforts to improve CNT dispersion as well as enhance the CNT-polymer interfacial bond (10,27-29). However, although chemical functionalization can lead 

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Common traditional approaches for the fabrication of CNT-polymer composites include solution processing of composites, melt spinning, melt processing, in situ polymerization, processing of composites based on thermosets, electrospinning and coagulation spinning for composite fibers and yam production [92]. 

In this Section we will discuss and compare mechanical properties of selected reported nanotube-polymer composites. We are going to focus on functionalisation of nanotubes and polymer composite fabrication techniques as the two main factors which have the strongest influence on the mechanical properties of CNT-polymer composites. 

Researchers examined the effect of solvent selection on the mechanical properties of CNT/polymer composites fabricated from double-walled nanotubes and polyvinyl alcohol in different solvents. It was shown that solvent selection can have a dramatic effect on the mechanical properties of CNT/polymer composites. Also, a critical... 

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. 

Early, in situ radical polymerization was used for the synthesis of poly(methyl methacrylate) (PMMA)-CNT composites [82]. In situ polymerization was performed using the radical initiator 2,2-azobisisobutyronitrile(AIBN). In this reaction, p-bonds in CNTs were initiated by AIBN, and therefore nanotubes could participate in PMMA polymerization to form a strong interface between the CNT and the PMMA matrix. PA6/CNT composites have been prepared by in situ polymerization of e-caprolactam in the presence of pristine and carboxylated CNTs. The e-caprolactam monomer was found to form an electron-transfer complex with CNTs and result in a homogeneous, polymerizable solution. The final composites can be spun into PA6/CNT fibers (Fig. 7) with excellent mechanical and electrical properties [83].This method is also suitable for the fabrication of thermosetting polymer composites with nanofillers. Bauhofer et al. [84] dispersed CNTs in an epoxy solution system based on a bisphenol-A epoxy resin and an amine hardener During nanocomposite curing, electric fields were used to induce the formation of aligned conductive nanotube networks. Recently, the in situ polymerization method... 

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. 

The chapter focuses on the studies that have been carried out on the processing and properties of CNT-PMMA composites. The various composite fabrication methods used by different researchers have been described followed by a discussion of the mechanical, electrical and thermal properties of CNT-PMMA composites. The key issues of CNT dispersion and interfacial adhesion between CNT and polymer matrix that are essential to develop these advanced composites have also been discussed. Some new ideas in this direction have also been proposed. 

A number of studies on CNT-polymer composites have focused on improving the dispersion and load transfer efficiency in other words the compatibility between the CNTs and polymer matrix through covalent chemical functionalization of CNT surface (12,40). Many of the studies reported above have used acid-functionalized CNTs to fabricate MWCNT-PMMA composites with improved mechanical properties using different processing methods (24,25,27,62). Yang et. al (68) modified the acid functionalized CNTs with octadecylam-ine (ODA) to obtain ODA-functionalized CNTs. These CNTs were reinforced in a copolymer P(MMA-co-EMA) to form composites with improved dispersion and mechanical properties. 

Though numerous groups have fabricated CNT-polymer composites, mechanical behaviour has not been the main focus of such studies. The bulk of the work has focused on studying the effect of the addition of CNT on the crystallization behaviour and on the electrical conductivity and improving dispersion by employing different techniques, as described earlier. 

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