Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Co-crystallization is the phenomenon by which chains of different crystallizabilities
crystallize at the same temperature. Co-crystallization is frequently observed in the blends of
different types of polyethylene. It is believed that co-crystallization can occur due to the
thermodynamically miscible parts of two components in the blends having similar
crystallization rate.
The study focused on the phenomenon of co-crystallization in polyethylene blends and how
by varying the crystallization conditions the co-crystallization region will change.
Three techniques have been used in this study. TREF was used to fractionate the polymers
and blends. Each of the TREF fractions was studied using both DSC and CRYSTAF to
determine whether the fraction contained both types of materials. It is shown that the
difference in the crystallization fractionation mechanisms between TREF, CRYSTAF and
DSC can be utilize to study co-crystallization effects in polyethylene blends.
Results also shows that by varying the heating and cooling rate profiles in DSC and
CRYSTAF the co-crystallization fractions will appeared as a single fraction or as two separate
fractions. Further, it was demonstrated how the co-crystallization area could be illustrated
using a unique 3-dimensional plot where the data from the prep-TREF fractionation, and the
DSC and CRYSTAF, were combined to give the “crystallization map” of the blend. These
plots give a quiche visual illustration of any co-crystallization regions in the blends as well as
how much the crystallization conditions effect the blend crystallization.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/2733 |
| Date | 03 1900 |
| Creators | Sweed, Muhamed |
| Contributors | Mallon, P. E., University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Stellenbosch |
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