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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Reinforcing Efficiency of Carbon Nanotubes in Poly (vinyl alcohol) Composites

Author: WANG, Zhujuan

Year: 2008

Supervisor(s): Ton Peijs

In this work, the reinforcing efficiency of carbon nanotubes in Poly (vinyl alcohol) (PVA) composites has been studied. Homogeneous single-walled carbon nanotubes (SWNT) / PVA nanocomposite films were first prepared by a solution-casting method using DMSO as a solvent. The solution-cast films were drawn in the solid state to create uniaxial nanocomposites where polymer chains and the SWNTs are highly aligned. Mechanical properties studies show a remarkable increase in Young’s modulus and tensile strength with the addition of SWNTs. For example, the addition of only 1.0 wt.% of SWNTs led to an astonishing 200% increase in tensile strength. Micromechanical analysis showed that the nanotube contribution to the composite strength was as high as 88 GPa, which starts to exploit the extraordinary theoretical strength of the CNTs. This high reinforcing efficiency suggests that in current systems most of the prerequisites for obtaining highly efficient nanocomposites are fulfilled, i.e. (i) a high level of dispersion, (ii) good interfacial interaction, and finally (iii) a high level of alignment of the nanofillers. X-ray studies demonstrated that the observed improvements in mechanical properties were true reinforcing effects of the SWNTs and not the result of modification of the PVA matrix. We employed the same method to prepare PVA nanocomposite tapes filled with different types of carbon nanotubes. Mechanical tests suggested different reinforcing behaviour in composite tapes. Crystallinity studies and X-ray studies confirmed that polymer morphology had been changed by the addition of double-walled carbon nanotubes and multi-walled carbon nanotubes. It was found that the reinforcing efficiency is influenced by the structure of the tubes, modification of the polymer matrices induced by nanotubes and the interaction between the polymer and the tubes.

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