The effect of degraded LDPE (dLDPE) as compatibilizer on the morphology, as well as
thermal, mechanical, and thermo-mechanical properties, of LDPE/wood flour (WF)
composites was investigated in this study. The composites were prepared through melt
mixing in a Brabender Plastograph internal mixer, while the LDPE was thermally degraded in
an air oven at 80 ï°C for different periods of time. The formation of functional groups on the
polyethylene chains during the degradation enables the dLDPE to be used as a compatibilizer.
Composites with different amounts of WF, compatibilized with dLDPEs having different
carbonyl indices, were characterized with scanning electron microscopy (SEM), Fouriertransform
infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), differential
scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical
analysis (DMA), as well as tensile, impact and hardness testing. Addition of dLDPE as
compatibilizer generally enhanced the mechanical properties of the composites. The SEM
images show smooth surfaces with fewer voids and fibre pullout for the dLDPE modified
composites. The FTIR results show an increase in carbonyl index up to 7 weeks degradation,
and the GPC results show that the molecular weight decreased significantly with increasing
degradation time. The DSC results show that the presence of WF particles, and increasing
filler loading, had very little influence on the melting and crystallization behaviour of the
untreated LDPE/WF composites. However, in the dLDPE treated composites a nucleating
effect of the fibres gave rise to increased LDPE melting and crystallization enthalpies. There
was no significant improvement in the thermal stability of the dLDPE treated composites.
The DMA results show that the presence of dLDPE (especially the 7 weeks dLDPE with a
carbonyl index of 0.90) observably influenced the viscoelastic properties of the composites.
In summary, it was found that the higher carbonyl index dLDPEs are more efficient
compatibilizers in LDPE/WF composites, despite their significantly reduced molecular
weights.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-09172013-093724 |
| Date | 17 September 2013 |
| Creators | Ndlovu, Sibusiso Sibongiseni |
| Contributors | Prof AJ van Reenen, 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-09172013-093724/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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