In this work sisal nanowhiskers (SNW) extracted from sisal fibres were used to reinforce
polyethylene matrices, high-density polyethylene (HDPE) and low-density polyethylene
(LDPE). The nanocomposites were prepared by solution casting from toluene and meltmixing,
both followed by melt pressing. In the case of melt mixing, the surfaces of the SNW
were also chemically modified with 1 phr of triethoxy vinyl silane (VTES) to improve their
dispersibility and compatibility with the matrices. The nanocomposites and sisal
nanowhiskers were characterized by Fourier transform infrared (FTIR) spectroscopy,
transmission electron microscopy (TEM), scanning electron microscopy (SEM),
thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic
mechanical analysis (DMA) and X-ray diffractometry (XRD). The sisal nanowhiskers,
obtained through sulphuric acid hydrolysis treatment, had average lengths of 197 ± 75 nm
and diameters of 12.2 ± 3.7 nm, and a crystallinity index of 89%. FTIR confirmed the surface
chemical modification of the sisal nanowhiskers. The microscopic techniques demonstrated a
fairly good dispersion of the whiskers in the matrices, regardless of the treatment or the
preparation method. The storage modulus for the solution mixed nanocomposites was better
than the untreated melt mixed nanocomposites. This behaviour was ascribed to the formation
of a rigid cellulosic network during processing. For the treated melt mixed samples, the
reinforcing effect was worse, suggesting the absence of a strong mechanical network because
of the good interaction between the whiskers and the host polymer matrix. TGA revealed that
there was no significant influence on the degradation behaviour of both polymers. The
crystallization behaviour of the polymers was found to strongly depend on their
morphologies. The melting and crystallization behaviour of the LDPE nanocomposites were
almost unchanged, while an increase in crystallinity was observed for all the HDPE
nanocomposites. The tensile properties depended on the type of polymer, the treatment, and
the preparation method. Generally there was an improvement in tensile modulus, and a
decrease in elongation at break, but the stress at break only improved for the HDPE
nanocomposites.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08262013-151200 |
| Date | 26 August 2013 |
| Creators | Mokhena, Teboho Clement |
| 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-08262013-151200/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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