Melt compounding was used to prepare polycarbonate (PC) and poly(methyl methacrylate)
(PMMA) nanocomposites with different amounts of metal-oxide fillers (silica, zirconia and
titania). Zirconia and two types of titania were prepared by a sol-gel method, whereas a
commercial hydrophobic silica having chemically surface bonded methyl groups was used.
Titania nanoparticles were annealed at 200 and 600 °C to obtain the anatase and rutile phases,
respectively. The effect of filler amount, in the range 1-5 wt.%, on the morphology, mechanical
properties and thermal degradation kinetics was investigated by means of transmission electron
microscopy (TEM), X-ray diffractometry (XRD), small-angle X-ray scattering (SAXS),
dynamic mechanical analysis (DMA), thermogravimetric analyses (TGA), Fourier-transform
infrared spectroscopy (FTIR), 13C cross-polarization magic-angle spinning nuclear magnetic
resonance spectroscopy (13C{1H}CP-MAS NMR) and measures of proton spin-lattice relaxation
time in the rotating frame (T1Ï(H)), in the laboratory frame (T1(H)) and cross polarization times
(TCH).
Results showed that the nanoparticles were well dispersed in the polymers whose structure
remained amorphous, except for zirconia in a PC matrix, which showed the appearance of a
local lamellar order around the nanoparticles. The silica, titania and zirconia nanopaticles
increased the thermal stability of the polymers, except for the highest silica and zirconia
contents in the PC system which showed a decrease. A similar trend in the activation energies of
thermal degradation was observed. The presence of zirconia and silica showed a decrease in the
storage and loss moduli at lower temperatures, probably due to a plasticization effect. The two
types of titania nanoparticles influenced the rigidity of the polymers in different ways because
of their different carbon contents, particle sizes and crystal structures. NMR results suggested
that, in the presence of a metal oxide, the observations in the PMMA systems could be related to
heteronuclear dipolar interactions between the carbonyl carbons and the surrounding hydrogen
nuclei, and in the PC systems to intermolecular interactions involving the carbonyl groups.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08262013-150849 |
| Date | 26 August 2013 |
| Creators | Motaung, Tshwafo Elias |
| Contributors | Prof AS Luyt |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-08262013-150849/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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