Thermoplastic-based conductive composites containing multi-wall carbon nanotubes aligned under the application of external electric fields

dc.contributor.authorOsazuwa, Osayukien
dc.contributor.departmentChemical Engineeringen
dc.contributor.supervisorDocoslis, Aristidesen
dc.contributor.supervisorKontopoulou, Mariannaen
dc.date2014-11-03 11:10:28.272
dc.date.accessioned2014-11-05T17:35:45Z
dc.date.available2014-11-05T17:35:45Z
dc.date.issued2014-11-05
dc.degree.grantorQueen's University at Kingstonen
dc.descriptionThesis (Ph.D, Chemical Engineering) -- Queen's University, 2014-11-03 11:10:28.272en
dc.description.abstractThe objective of this thesis is to prepare thermoplastic/multi-wall carbon nanotubes (MWCNTs) and to apply external alternating current (AC) electric fields to achieve enhanced conductivity and dielectric properties. The first part of the thesis focuses on preparing polyolefin-based composites containing well-dispersed MWCNTs. MWCNTs are functionalized with a hyperbranched polyethylene (HBPE) using a non-covalent, non-specific functionalization approach and melt compounded with an ethylene-octene copolymer (EOC) matrix. The improved filler dispersion in the functionalized EOC/MWCNT composite results in higher elongation at break compared to the non-functionalized composite. However, the electrical percolation threshold and the ultimate conductivity of the composites are not affected considerably, suggesting that this functionalization approach leaves the inherent properties of the nanotubes intact. EOC/HBPE-functionalized MWCNT composites are further subjected to external AC electric fields (35 – 212 kV/m), which induce the formation of aligned columnar structures, as evidenced by Scanning Electron Microscopy. Experimentally acquired resistivity data are used to derive correlations between the characteristic insulator-to-conductor transition times of the composites and the electric field strength (E), polymer viscosity (η) and MWCNT volume fraction (ϕ). A criterion for the selection of (η, E, ϕ) conditions that enable MWCNT assembly under an electric field controlled regime (minimal Brownian motion-driven aggregation effects) is developed. The dielectric properties of the solidified aligned EOC/MWCNT composites are further studied using dielectric spectroscopy. Annealing of the composites at 160 oC results in the formation of interconnected structures, whereas electrification, using AC field of 71 and 212 kV/m induces the formation of aligned columnar structures. The electrified and annealed composites have increased real and imaginary permittivity compared to the as-compounded composite, resulting in improved conductivity and storage capacity. An equivalent circuit model is fitted to the experimentally obtained impedance data in order to correlate the effects of electric field and processing time to the dielectric characteristics of the treated composites. Finally poly(ethylene succinate) (PESu) composites containing well-dispersed MWCNT were prepared by an in-situ polymerization method. Composite electrification results in improvements in the electrical conductivity by up to 12 orders of magnitude, and a retention of high conductivity in the solidified state.en
dc.description.degreePhDen
dc.identifier.urihttp://hdl.handle.net/1974/12606
dc.language.isoengen
dc.relation.ispartofseriesCanadian thesesen
dc.rightsThis publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.en
dc.subjectCompositesen
dc.subjectAC electric fieldsen
dc.subjectCarbon nanotubesen
dc.subjectElectrical conductivityen
dc.subjectFiller alignmenten
dc.subjectThermoplasticen
dc.titleThermoplastic-based conductive composites containing multi-wall carbon nanotubes aligned under the application of external electric fieldsen
dc.typethesisen
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