This study focuses on understanding the photochemical reactions that occur between ultraviolet stabilizers and lignin during irradiation in order to further comprehend the photo-protection mechanisms of these stabilizers during brightness reversion. The stabilizers chosen for study included a variety of ultraviolet absorbers (UVAs), in addition to a hindered nitroxide free radical (4-hydroxy-TEMPO). Irradiated samples were analyzed using quantitative 31P NMR, in addition to a technique known as 'Derivatization Followed by Reductive Cleavage'. / Benzophenone-based UVAs have been shown to be actively involved in photochemical reactions with lignin during irradiation, while benzotriazole-based UVAs are comparatively photostable under identical irradiation techniques. All additive combinations were found to inhibit the formation of carboxylic acids and photochemical condensation reactions in lignin; however, the joint application of 2,4-DHB and 4-hydroxy-TEMPO demonstrated synergistic inhibition of these reactions. / All additive combinations were shown to impede the formation of catechol structures and to retard the cleavage of lignin beta-arylether groups during irradiation. The combined use of Tinuvin 1130 and 4-hydroxy-TEMPO provided the most efficient inhibition of these reactions. These results provide insight into the excellent photoyellowing inhibition provided by this additive combination when applied onto mechanical pulps.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.32897 |
| Date | January 2000 |
| Creators | Beaton, Christa. |
| Contributors | Argyropoulos, Dimitris S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Chemistry.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001781985, proquestno: MQ70772, Theses scanned by UMI/ProQuest. |
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