The correlation of the molecular structure of polyolefins with environmental stress cracking resistance

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dc.contributor.advisor Van Reenen, Albert J. Shebani, Anour Nasser en_ZA
dc.contributor.other University of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science. 2008-07-29T09:11:08Z en_ZA 2010-06-01T08:57:26Z 2008-07-29T09:11:08Z en_ZA 2010-06-01T08:57:26Z 2006-12 en_ZA
dc.description Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006.
dc.description.abstract This study concerns the phenomenon of environmental stress cracking resistance (ESCR) in three impact polypropylene copolymers (IPPCs). The main purpose was to correlate the ESCR with their properties such as microstructure, molecular weight (MW), molecular weight distribution (MWD), crystallinity and morphology. Initially the selection of a suitable test method and an active stress cracking agent (SCA) were the preliminary concerns. The Bell telephone test was used to evaluate SCAs, while a published procedure for determining ESCR of ethylene based plastics was adapted for the purpose of this study. Isopropanol was selected as SCA. Polymers were fully characterized by FTIR, 13C NMR, DSC and high temperature GPC. Optical microscopy was used to investigate craze formation and crack growth, and scanning electron microscopy (SEM) was used to study the morphology of the polymers. Since IPPCs are known to have multi-fraction copolymeric structures and each of these fractions has significantly different average properties, fractions were selectively removed from the materials, either by solvent extraction at room temperature, or by TREF fractionation. The effect of removing these fractions on the ESCR was determined. The effect of the molecular composition of the three IPPCs on the ESCR of these materials, as well as the effect of the removal of the selected molecular fractions on the ESCR, morphology and molecular characteristics are discussed and compared. Conclusions are drawn as to the factors controlling ESCR in these materials. en_ZA
dc.language.iso en en_ZA
dc.publisher Stellenbosch : University of Stellenbosch
dc.subject Environmental stress cracking (ESR) en_ZA
dc.subject Impact polypropylene copolymer en_ZA
dc.subject Environmental stress cracking resistance (ESCR) en_ZA
dc.subject Dissertations -- Polymer science en_ZA
dc.subject Theses -- Polymer science en_ZA
dc.subject.other Chemistry and Polymer Science en_ZA
dc.title The correlation of the molecular structure of polyolefins with environmental stress cracking resistance en_ZA
dc.type Thesis en_ZA
dc.rights.holder University of Stellenbosch
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