Phase change material (PCM) composites based on high-density polyethylene (HDPE) with
soft (M3) and hard (H1) Fischer-Tropsch paraffin waxes and alkali-treated wood flour (WF)
were investigated in this study. Both the blends and composites were prepared using a meltmixing
method with a Brabender-Plastograph. SEM, DSC, TGA, DMA, tensile testing and
water absorption were used to characterize the structure and properties of the blends and
composites. The HDPE as the supporting matrix kept the molten waxes in compact shape
during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the
supporting matrix (HDPE) is a necessary property for effective energy storage. M3 wax
blends were immiscible, whereas H1 wax blends seemed to be partially miscible and cocrystallized
with the polymer matrix. In the presence of WF, the wax seems to crystallize
around and in the pores of the WF particles, thus reducing co-crystallization with the HDPE
and improving the energy storage capacity. TGA results showed a reduction in the thermal
stabilities of the blends and composites in the presence of both WF and waxes. The storage
modulus was reduced in the presence of wax, but improved when both WF and wax are
present, although the improvement was less significant in the case of the M3 wax. Depending
on the type of wax, the γ- and α-transitions were influenced differently, and there was an
emergence of a β-relaxation in the case of the M3 wax blends. Both waxes had different
influences on the tensile modulus and strength of the blends, with H1 increasing and M3
decreasing these properties. The PCM composites, on the other hand, had high moduli. High
content of WF in the composites showed high water absorption. However, in the wax
containing composites, there was a general decrease in water uptake.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-07232013-102946 |
| Date | 23 July 2013 |
| Creators | Mngomezulu, Mfiso Emmanuel |
| Contributors | Dr I Krupa, 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-07232013-102946/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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