Carbon nanotubes are known as ideal fillers for polymer systems; the main advantage of
carbon nanotubes over other nano-reinforcing particles is the combination of superior
strength and stiffness with large aspect ratio. Carbon nanotubes may improve the
mechanical, electrical and thermal properties of polymers, but to realise their potential
in polymer systems uniform dispersion, strong interfacial adhesion and alignment of
nanotubes within the polymer matrix are necessary. These properties are not easy to
achieve and they are key challenges in producing CNT/Polymer system. This research
was carried out in an attempt to understand how the properties of CNT/Polymer
composite can be optimised by manipulation of additives, compounding and postcompounding
conditions.
Polypropylene/Multi-Walled Carbon Nanotube (PP/MCNT) composites were prepared
by conventional twin screw extrusion. Dispersants and compatibilisers were used to
establish good interaction between filler and polymer. Several different extruder screw
configurations were designed and the properties of PP/MCNT composite prepared by
each configuration investigated. The results indicated that the addition of carbon
nanotubes without additives enhanced mechanical, electrical and thermal properties of
polypropylene polymer. Incorporation of compatibilisers into PP/MCNT improved the
stiffness but decreased the strength of the nanocomposite, whilst addition of dispersants
decreased the mechanical properties of the nanocomposite. Addition of both additives at
high concentration improved electrical conductivity and induced electrical percolation
in the nanocomposite.
Extruder screw configuration was found to have significant effect on the electrical
conductivity whilst only slightly affecting mechanical properties of the nanocomposite, possibly due to the competition between dispersion and degradation of polymer chains
and possible reduction of carbon nanotube length by intensive shear during
compounding. The use of screw configuration with high mixing intensity promoted the
dispersion of nanotubes and favoured the conduction process in the nanocomposite.
Finally in an attempt to improve dispersion and alignment of carbon nanotubes,
compounded PP/MCNT composite was subjected to micromoulding, fibre spinning and
biaxial stretching processes and the resultant properties investigated. Application of
post-compounding process was found to have significant effect on mechanical and
rheological properties of the nanocomposite. Stiffness and strength of the
nanocomposites treated by post-compounding processes were found to increase by up to
160% and 300%, respectively. The reinforcement effect of carbon nanotubes in the
stretched nanocomposites was found to be the greatest. Rheological analysis suggested
that the application of post-compounding processes enhanced dispersion of carbon
nanotubes within the nanocomposite.
Overall, this finding of this research has shown that carbon nanotubes can be
incorporated into polypropylene using conventional equipment to provide significant
improvement in properties. By careful choices of additives, compounding and postcompounding
conditions, specific properties can be further enhanced. / Ministry of higher education in Kurdistan region in Iraq.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/5703 |
| Date | January 2012 |
| Creators | Ezat, Gulstan S. |
| Contributors | Youseffi, Mansour, Kelly, Adrian L. |
| Publisher | University of Bradford, School of Engineering, Design and Technology |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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