Doctoral Degrees (Chemistry and Polymer Science)

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Browsing Doctoral Degrees (Chemistry and Polymer Science) by Author "Al-Aeeb, Ahmed Z."

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    Nanocolorants for hot-melt inks
    (Stellenbosch : Stellenbosch University, 2013-03) Al-Aeeb, Ahmed Z.; Klumperman, Bert; Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science.
    ENGLISH ABSTRACT: A new class of nanocolorants is described for the use as a colorant in hot-melt ink application for ink-jet printing technology. An inverse miniemulsion polymerization process was utilized successfully as a one-step encapsulation process to encapsulate the highly hydrophilic water-soluble fluorescent Rhodamine B dye (RhB) by the hydrophilic water-soluble poly(acrylamide) (PAAm). Three types of Rhodamine B-based nanocolorants, PAAm/RhB, crosslinked-PAAm/RhB and poly(AAm-co-Sty)/RhB, were synthesized using inverse miniemulsion polymerization. The PAAm/RhB nanocolorants exhibited solid dark nanoparticles morphology, while crosslinked-PAAm/RhB and poly(AAm-co-Sty)/RhB showed a core-shell type of morphology. The nanocolorants showed improved light and dye migration fastness as well as high thermal stability, especially, nanocolorants with core-shell morphology. The synthesis of polymerizable RhB-based nanocolorants is described. Poly(AAm-co-RhB) nanocolorants were successfully synthesized for the first time via inverse miniemulsion polymerization. RhB dye was first functionalized by esterification reaction to introduce an acrylate polymerizable group. The RhB-acrylate dye was copolymerized with AAm monomer in an inverse miniemulsion polymerization to produce nanocolorants with superior light and migration fastness. Crosslinked-poly(AAm-co-RhB) nanocolorants could be obtained based on the incorporation of a crosslinking agent. Poly(AAm-co-RhB) and crosslinked-poly(AAm-co-RhB) nanocolorants exhibited a morphology of dark solid and core-shell particles, respectively. In both nanocolorants, the RhB-acrylate dye was completely integrated by copolymerization into the polymer matrix, and by that, the dye migration was completely supressed. Both poly(AAm-co-RhB) and crosslinked-poly(AAm-co-RhB) nanocolorants showed high thermal stability as well as high Tg values. The syntheses of PAAm/RhB nanocolorants-based solid inks were carried out successfully via inverse miniemulsion polymerization. An in situ inverse miniemulsion polymerization, with the paraffin wax as the organic phase, was utilized in making a crosslinked-PAAm/RhB nanocolorants-based solid ink. A crosslinked-poly(AAm-co-RhB) nanocolorants-based solid ink was prepared by the direct mixing of the readymade crosslinked-PAAm/RhB nanocolorants (suspended in cyclohexane) with paraffin wax at temperature above the melting temperature of the wax until all the cyclohexane evaporated. The obtained solid inks appeared as a solid homogenous waxy material with a deep bright colour reflecting that the nanocolorants were well dispersed in the wax. DSC thermograms showed that the solid inks have one sharp melting transition indicating the applicability of our nanocolorants for hot-melt ink applications.