Nanocolorants for hot-melt inks

Al-Aeeb, Ahmed Z. (2013-03)

Thesis (PhD)--Stellenbosch University, 2013.

Thesis

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.

AFRIKAANSE OPSOMMING: ‘n Nuwe reeks nonokleursels word beskryf vir die gebruik in ink-smelt drukker tegnologie. Inverse minie-emulsie polymerisasie was suksesvol gebruik om die kleurstof Rhodamine B (RhB) in die water oplosbare poly(akrielamied) (PAAm) te enkapsuleer. Die roete is gebruik om drie tipes kleurstof te produseer. Elk van die kleurstowwe was gebaseer op Rhodamine B en ‘n PAAm, naamlik PAAm/RhB, kruisgebonde PAAm/RhB en poli(akrielamied-ko-stireen)/RhB. PAAm/RhB nanokleursel was in die vorm van soliede donker nanopartikels. Die kruisgebonde PAAm/RhB en poli(akrielamied-ko-stireen) het bestaan uit nanoparikels met ‘n kern en skil morfologie. Die nanokleursels het ‘n verbetering in terme van lig en hitte stabiliteit getoon. Die migrasie van kleursel uit die nanopartikels, veral die met kern en skil morfologie, was baie minder. Die sintese van ‘n polimeeriseerbare nanokleursel gebaseer op RhB word beskryf. Poly(AAm-ko-RhB) nanokleursels was vir die eerste keer suksesvol gesintetiseer met behulp van ‘n inverse minie-emulsie polimerisasie. RhB kleursel was eers gefunksionaliseer deur middel van ‘n esterifikasie reaksie om ‘n polimeeriseerbare akrilaat groep te verkry. Die RhB-akrilaat kleursel was gekopolimeeriseer met AAm monomeer in ‘n inverse minie-emulsie polimerisasie om nanokleursels met verbeterde lig en migrasie stabiliteit te verkry. Kruisgebonde poli(AAm-ko-RhB) nanokleursels was verkry deur ‘n geskikte verbinding in die reaksie mengsel by te voeg. Beide poli(AAm-ko-RhB) and kruisgebonde poly(AAm-ko-RhB) nanokleursels was verkry as donker partikels met ‘n kern en skil morfologie. In beide gevalle was die RhB-akrilaat kleursel deeglik geintegreer in die matriks en sodoende was die migrasie van die kleursel heeltemal onderdruk. In albei gevalle het poli(AAm-ko-RhB) en kruisgebonde poli(AAm-ko-RhB) nanokleursels hoë hitte stabiliteit en hoë Tg waardes getoon. Die sintese van nanokleursels gebaseer op PAAm/RhB was sukselvol uit gevoer via inverse minie-emulsie polimerisasie. ‘n In situ inverse minie-emulsie polimerisasie met paraffin waks as die organiese fase was gebruik om soliede ink te produseer wat opgemaak is uit kruisgebonde PAAm/RhB nanokleursel. Die kruisgebonde poli(AAm-ko-RhB) soliede ink was voorberei deur die kruisgebonde PAAm/RhB nanokleursels (in suspensie met sikloheksaan) direk met die paraffin waks te meng by ‘n temperatuur hoër as die smeltpunt van die waks todat al die sikloheksaan verdamp het. Die soliede ink was verkry as ‘n homogene waksagtige materiaal met ‘n diep en helder kleur wat ‘n aanduiding was dat die nanokleursels goed versprei was in die waks. DSC termogramme het bewys dat die ink slegs een skerp smelt punt oorgang het wat beteken dat die materiaal geskik is om te gebruik in ink-smelt drukkers.

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