Mechanical Properties of CNT Polymer Composites

Influence of Nanotube Functionalisation on Mechanical Properties of CNT-Polymer Composites... 

GPa. In our calculations, densities of nanotubes used were assumed to be p = 1350 kg m for SWNTs and p = 2150 kg for MWNTs. ° There are a huge amount of variables that effect the mechanical properties of CNT-polymer composites including type of CNTs used choice of solvent nanotube functionality polymer used composite preparation As this procedure... 

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. 

In this Section we discuss mechanical properties of CNT polymer composites produced by melt processing. Although a number of papers have reported this approach, we will only discuss those which reported highest values of dI7 dFf. 

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... 

TABLE 23.5 Theoretical approaches on predicting the mechanical properties of CNT-polymer composite [46],... 

Many reports [87,92,93] showed that there is a critical CNT content in the matrix below which the strengthening effect of CNT-polymer composites increases with increasing CNT content. Above this critical CNT content, however, the mechanical properties of CNT-polymer composites decrease, and in some cases, they decrease below those of the neat matrix material. These observations can be attributed to (i) the difficulties associated with uniform dispersion of CNTs at high CNT contents and (ii) the lack of polymerization reactions that are adversely affected by the high CNT content. The latter effect becomes more pronounced when functionalized CNTs are employed to produce CNT-polymer nanocomposites [88]. 

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

Table 4.3 Mechanical properties of selected polymer composites containing functionalised CNTs. 

The CNT/polymer nanocomposites can be fabricated by means of solution blending, in situ polymerization and melt compounding [33-39]. The properties of CNT /polymer nanocomposites are directly related to their hierarchical microstructures. The processing conditions and polymers selected dictate the morphology, structure, electrical and mechanical properties of CNT/polymer nanocomposites. In addition, exfoliation and homogeneous dispersion of CNTs in the polymer matrix also play important roles in electrical properties of the composites. The agglomeration of nanotubes is detrimental to the formation of a conductive path network through the matrix of percolative CNT/polymer nanocomposites. 

Another parameter influencing the mechanical properties of nanotube composites is the CNT alignment. The effects of CNT alignment on electrical conductivity and mechanical properties of CNT-polymer nanocomposites have been discussed in a number of researches [118-120]. For example, it has been reported that with increasing CNT alignment, the electrical and mechanical properties of the SWNT-epoxy composites increased due to an increased interface bonding of CNTs in the polymer matrix [119],... 

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. 

The desirable mechanical properties of CNTs have been exploited in recent years for the structural reinforcement of polymers.This is a natural extension of traditional composite materials used for applications that require both high-strength... 

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