Multiwalled carbon nanotube tensile properties

Kwon et al. compared WPU/MWNT with WPU/nitric acid treated multiwalled carbon nanotube (A-CNT) composites (20). The tensile strength and modulus of the WPU/A-CNT composites were higher than those of the WPU/MWNT composites with the same CNT content. The better mechanical properties of WPU / A-CNT composites can perhaps be attributed to higher content of polar groups of A-CNTs thus inducing higher interfacial interactions between A-CNTs and WPU chains. 

Recently, reinforcement of chitosan film with carbon nanotubes was tested. This composite demonstrates a large increase in the tensile modulus with the incorporation of only 0.8% of multiwalled carbon nanotubes [133]. Many papers concern bio-inorganic composites, including hydroxyapatite, which increases the mechanical properties and mimics the nanostructure of bone [88, 134, 135]. 

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. 

Xiao et al. [59] carried out a detailed study of the mechanical and rheological properties of low-density polyethylene reinforced by the incorporation of multiwalled carbon nanotubes. It was found that the Young s modulus and tensile strength of the composites can increase by 89% and 56%, respectively, when the nanotube loading reaches 10 wt%. The curving and coiling of multiwalled carbon nanotubes play an important role in the enhancement of the composite modulus. It was also found that the materials experience a fluid-solid transition at the composition of 4.8 wt%, beyond which a continuous multiwalled carbon nanotube network forms throughout the matrix and in turn promotes the reinforconent of the multiwalled carbon nanotubes. 

The first carbon nanotubes discovered in nature, such as those produced in Iijima s experiments, were multiwalled nanotuhes (MWNT). Multiwalled nanotuhes consist of a number of concentric carbon cylinders, a set of tubes nested inside each other. They are somewhat complex systems that are relatively difficult to study. An important step forward in research on carbon nanotuhes occurred in 1993, when scientists learned how to make single-walled nanotubes (SWNT). Using the simpler SWNTs, scientists have learned quite rapidly a great deal about the electrical conductivity, tensile strength, flexibility, toughness, and other physical properties of carbon nanotuhes. 

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