Publication: Preparation of novel thioxanthone based polymeric photoinitiator for flexographic varnish and determination of their migration behaviour
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Date
2018
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ELSEVIER SCIENCE SA
Abstract
Today, polymeric photoinitiators are good choice for initiation mechanism of UV-curable printing inks with their low migration potential. In this study, new thioxanthone-styrene polymeric photoinitiators were synthesized. Polystyrene that was synthesized by atom transfer radical polymerization (ATRP) was functionalized by cyclohexeneoxide and then reacted with thioxanthone-thioacetic acid. Piperazine was reacted with bromine chain end of polystyrene and final polymeric photoinitiator was obtained. Proton Nuclear Magnetic Resonance (H-1 NMR), Attenuated Total Reflectance- Fourier Transform Infrared Spectroscopy (ATR-FTIR), Gel Permeation Chromatography (GPC) and Ultraviolet-Visible Spectroscopy (UV-vis) analyses were confirmed the expected structures. The curing property of new polymeric photoinitiator was compared with a conventional thioxanthone printing formulation that is used in flexographic varnish. The photopolymerization kinetics were determined by Photo Differential Scanning Calorimetry (Photo-DSC) and the results showed that 83% of conversion was reached for thioxanthone-styrene polymeric photoinitiator with MW = 4200. The migration behavior was identified with Liquid Chromatography-Mass Spectrometry LC-MS. It was shown that thioxanthone based polymeric photoinitiator is usable in flexographic varnish and thioxanthone migration level is reduced with macrophotoinitiation.
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Keywords
Polymeric photoinitiator, Photopolymerization, Thioxanthone, Migration, Flexographic varnish, FREE-RADICAL POLYMERIZATION, SIDE-CHAIN THIOXANTHONE, COINITIATOR AMINE, NANOCOMPOSITES