Synthesis and characterization of cationically and anionically modified poly(vinyl alcohol) microfibrils

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dc.contributor.advisorSanderson, R. D.en_ZA
dc.contributor.authorChirowodza, Helenen_ZA
dc.contributor.otherUniversity of Stellenbosch. Faculty of Science. Dept. of Chemistry and Polymer Science.
dc.date.accessioned2009-02-10T13:01:41Zen_ZA
dc.date.accessioned2010-06-01T08:42:42Z
dc.date.available2009-02-10T13:01:41Zen_ZA
dc.date.available2010-06-01T08:42:42Z
dc.date.issued2009-03en_ZA
dc.descriptionThesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009.en_ZA
dc.description.abstractIn papermaking, the addition of filler can be detrimental to the properties of the resulting paper hence the use of additives that enhance paper properties are of paramount importance. Syndiotacticity rich poly(vinyl alcohol) (PVA) microfibrils were prepared for use as filler retention aids. They were prepared via in situ fibrillation during the saponification of high molecular weight poly(vinyl pivalate). The resulting fibers had high thermal stability and crystalline melting temperature. They were not fully soluble in water even at 100 oC. In order to make them less water resistant the syndiotacticity of the PVA microfibrils was varied by copolymerizing vinyl pivalate with vinyl acetate and saponifying the resultant copolymer. It was observed that changes in syndiotacticity had a significant effect on the crystallinity, morphology and thermal properties of the resultant PVA. The surfaces of the fibers were modified by first crosslinking using glyoxal (a dialdehyde), and then attaching cationic and anionic groups by grafting and by carboxymethylation. Crosslinking prior to modification was beneficial in minimizing the solubility of the fibers in the aqueous media in which they were modified. Heterogeneous modification techniques were employed so that fiber properties could be preserved. Carboxymethylation was carried out using the two step Williamson’s ether synthesis. The first step involves the formation of a highly reactive alkoxide by the reaction of PVA with a strong base and the second its etherification using a functional alkyl halide. Poly(methacryloyloxy ethyl trimethyl ammonium chloride) and poly(acrylic acid) were grafted from the PVA microfibrils using the KPS/Na2S2O3 redox initiation system. Grafting was confirmed by FTIR and NMR spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out on both modified and unmodified PVA microfibrils. The results showed that crosslinking resulted in an enhancement of the thermal properties of the microfibrils. A decline in the onset temperature for thermal degradation and crystalline melting temperature were observed, and were attributed to the modification of the PVA microfibrils.en_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/2184
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : University of Stellenbosch
dc.rights.holderUniversity of Stellenbosch
dc.subjectPolyvinyl alcoholen_ZA
dc.subjectFibersen_ZA
dc.subjectPolymersen_ZA
dc.subjectPVA stereoregularityen_ZA
dc.subjectDissertations -- Polymer scienceen_ZA
dc.subjectTheses -- Polymer scienceen_ZA
dc.subject.otherChemistry and Polymer Scienceen_ZA
dc.titleSynthesis and characterization of cationically and anionically modified poly(vinyl alcohol) microfibrilsen_ZA
dc.typeThesisen_ZA
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