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Factors influencing the efficiency of photoinitiation in radiation curable ink formations

Herlihy, Shaun Lawrence (1997) Factors influencing the efficiency of photoinitiation in radiation curable ink formations. Doctor of Philosophy (PhD) thesis, University of Kent. (doi:10.22024/UniKent/01.02.86240) (KAR id:86240)

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https://doi.org/10.22024/UniKent/01.02.86240

Abstract

In an effort to be able to use photoinitiators to their maximum potential, the sequence of events that occurs in an ink formulation during the UV curing process has have been studied and information presented to allow more effective formulation. Emphasis has been placed on highlighting the variables that have the greatest impact both on photoinitiator efficiency and on the suitability of individual photoinitiators and synergists for use in particular applications. These variables were found to be photoinitiator thermal stability, UV light utilisation, reaction mechanisms and cure reactivity.

A wide range of photoinitiators and synergists were investigated using thermogravimetric analysis (TGA) and thermogravimetric analysis-mass spectroscopy (TGA-MS) to define both their thermal stability and whether under heating they thermally decompose or merely evaporate.

Differential photocalorimetry (DPC) was used to determine which wavelengths from a typical medium pressure mercury curing lamp are the most important for providing cure, with both theoretical and practical methods being used to define the extent to which these wavelengths penetrate into pigmented and non-pigmented coatings. A procedure was devised and validated for this purpose.

The reaction mechanism and photodecomposition products of a range of photoinitiators were investigated using gas chromatography-mass spectroscopy (GC-MS) and radical trapping experiments. The reaction mechanisms are discussed in terms of available literature knowledge. Evidence is also presented suggesting that, with only particular exceptions, cleavage photoinitiators can also react by a hydrogen abstraction mechanism in the presence of an amine synergist.

A real time infrared spectrometer (RTIR) was set up and a method validated for following the UV curing reaction through changes in the acrylate double bond concentration. The advantages and disadvantages of this instrument are discussed in terms of other similar instruments reported in the literature, and the technique subsequently used to measure the reaction rates of a wide range of photoinitiators. Other factors such as photoinitiator concentration, amine synergist type I level and formulation viscosity were also investigated to determine their influence on the cure process.

Item Type: Thesis (Doctor of Philosophy (PhD))
DOI/Identification number: 10.22024/UniKent/01.02.86240
Additional information: This thesis has been digitised by EThOS, the British Library digitisation service, for purposes of preservation and dissemination. It was uploaded to KAR on 09 February 2021 in order to hold its content and record within University of Kent systems. It is available Open Access using a Creative Commons Attribution, Non-commercial, No Derivatives (https://creativecommons.org/licenses/by-nc-nd/4.0/) licence so that the thesis and its author, can benefit from opportunities for increased readership and citation. This was done in line with University of Kent policies (https://www.kent.ac.uk/is/strategy/docs/Kent%20Open%20Access%20policy.pdf). If you feel that your rights are compromised by open access to this thesis, or if you would like more information about its availability, please contact us at ResearchSupport@kent.ac.uk and we will seriously consider your claim under the terms of our Take-Down Policy (https://www.kent.ac.uk/is/regulations/library/kar-take-down-policy.html).
Uncontrolled keywords: UV curing; Photoinitiators
Subjects: Q Science > QD Chemistry
Divisions: Divisions > Division of Natural Sciences > Chemistry and Forensics
SWORD Depositor: SWORD Copy
Depositing User: SWORD Copy
Date Deposited: 29 Oct 2019 16:37 UTC
Last Modified: 16 Nov 2021 10:27 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/86240 (The current URI for this page, for reference purposes)
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