The effects of dicumyl peroxide/vinyltriethoxysilane (DCP/VTES) treatment, nanoclay
content and the nature of the nanoclay were investigated for low-density polyethylene
(LDPE)/clay and high-density polyethylene (HDPE)/clay nanocomposites. LDPE was treated
with 0.1 phr of DCP with respectively 1 phr and 3 phr VTES (System A), and with 0.2 phr of
DCP with the same amounts of VTES, and then mixed with different contents (1, 3, and 5 wt.
%) of modified (Cloisite 15A) and unmodified (calcium montmorillonite) clay. The HDPE
nanocomposites were prepared according to System A, using Cloisite 15A. The polymer-clay
nanocomposites were prepared through melt mixing in a Brabender Plastograph internal
mixer, and were characterized for their morphology, thermal properties, mechanical
properties, thermomechanical properties and the extent of grafting/crosslinking. FTIR
analysis clearly showed that grafting in System A was not very effective, and that the
âgraftedâ LDPE contained an appreciable amount of ungrafted (pure or hydrolysed) VTES.
However, sufficient grafting was achieved in System B, but there was also a higher extent of
crosslinking. The XRD and TEM results showed that C15A was more intercalated than
Ca2+MMT showed, and also slightly exfoliated. Nanocomposites prepared according to
System A showed intercalated structures, while those prepared according to System B
showed partially exfoliated structures. The DSC results showed that the presence of
DCP/VTES decreased the melting temperature and crystallinity of both the polymer matrices
due to a decrease in lamellar thickness as a result of crosslinking between the polymer chains,
in addition to VTES grafting. The addition of clay and its nature had no significant influence
on the melting temperature and crystallinity of both polymers. The TGA results showed an
improvement in the thermal stability of all the nanocomposites, but the silane treated C15A
nanocomposites showed a higher degradation rate at higher clay contents. The mechanical
and thermomechanical properties of the untreated nanocomposites were better than those of
the treated nanocomposites at the same clay loading.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-08262013-152112 |
| Date | 26 August 2013 |
| Creators | Sibeko, Motshabi Alinah |
| 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-08262013-152112/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. |
Page generated in 0.0018 seconds