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The Application of Halloysite Nanotubes in Epoxy Resin Nanocomposites

Williams, R. J. (2019) The Application of Halloysite Nanotubes in Epoxy Resin Nanocomposites. PhD thesis, University of Sheffield.

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Abstract

Halloysite nanotubes are a type of naturally occurring clay nanoparticle which have attracted increasing research interest as reinforcing fillers in polymer nanocomposites. This thesis investigates some fundamental, but often overlooked, considerations for their application in epoxy resin nanocomposites specifically, with a view to moving towards the eventual scale-up of the production of such materials. Firstly, some chemical and physical properties of halloysite nanotubes were characterised, and the results compared to supplier and literature data. Measured values were frequently found to differ from those that were expected. Significant attention is paid to the challenges associated with measuring nanotube size and shape, and it is concluded that neither light scattering nor electron microscopy can be used to reliably find these values. However, automated computational analysis of electron micrographs is highlighted as a promising avenue for further work. Several methods for dispersing halloysite nanotubes into epoxy resin were assessed in terms of the degree of dispersion of the nanotubes, whether any damage had occurred during mixing, and the mechanical properties of the final nanocomposites. It was concluded that the use of a three-roll mill in force mode was the most effective mixing method, as it produced nanocomposites containing individually dispersed nanotubes which had an increased flexural modulus compared to pure epoxy resin. It was also found that several methods could be used to measure the filler content in these samples, including helium pycnometry and burning off the resin in air. Finally, coating of the nanotubes with alkoxysilane coupling agents was shown to be successful, but it was also found to be variable in terms of the grafted amounts and the wettabilities of the coated samples. Nonetheless, scaling the process up to tens of grams produced coated samples with similar properties to those made on the scale of grams. Inaddition, piranha solution pre- treatment of the nanotubes was demonstrated to not to be an effective means of increasing the grafted amount of alkoxysilane on the surface, in contradiction to previous literature.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Mechanical Engineering (Sheffield)
Identification Number/EthosID: uk.bl.ethos.800549
Depositing User: Mr Rhys Williams
Date Deposited: 09 Mar 2020 10:57
Last Modified: 01 Apr 2020 09:53
URI: http://etheses.whiterose.ac.uk/id/eprint/26071

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