Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589147
Title: Preparation and characterisation of flexographic inks
Author: Hamroush, Manal
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2012
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Abstract:
This study focuses on the preparation of nitrocellulose-based flexographic inks suitable for printing on biaxially- oriented polypropylene (BOPP), for which the adhesion of the manufactured ink to the BOPP substrate is an essential property of importance. The choice of BOPP as the main substrate in this study follows from its position as one of the more commonly used substrates for printing worldwide. The importance of using fumaric rosin UCH150H in preparation of flexographic inks resulted from the experience of using this resin in preparing flexographic polyamide inks, where the adhesion results were very good, when this resin was added to flexographic nitrocellulose inks, the adhesion was improved remarkebly. Two polymers are used in this study: fumaric rosin (UCH150H) and a polyurethane (Surkopak 5323) and many formulations were tested. The use of fumaric rosin to form flexographic inks instead of polyurethane was novel. When used in combination with polyurethane as an additive in nitrocellulose flexographic inks rather than titanium acetyl-acetonates (TAA,) this offers benefits, as (TAA,) has many disadvantages when used to prepare flexographic inks for printing on BOPP. Comparative tests of the adhesion of the inks to the substrate are carried out by tape test after printing the two prepared inks on BOPP and subjecting these to Corona treatment. The principal factor influencing the adhesion is found to be the polymer structure, and it is found that the inks prepared by using UCH150H exhibited better adhesion to the BOPP substrate than those prepared from Surkopak 5323. Analytical techniques were employed to provide information as to why the adhesion was superior when using the ink prepared from UCH150H, including wetting contact angle measurements, optical microscopy, scanning electron microscopy (SEM) and electron diffractive X-ray (EDX), atomic force microscopy (AFM), electronic scanning for chemical analysis (ESCA), Fourier Transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and inverse gas chromatography (IGC). The novelty in using IGC to study BOPP coated separately with UCH150H and Surkopak 5323 facilitates the comparison of physical properties associated with the polymer before and after printing on BOPP. Furthermore, the substitution of Surkopak 5323 by UCH150H is better for the environment as the latter is derived primarily from natural products (e.g. colophony from pine trees), while Surkopak 5323 is based on an isocyanate precursor which is no longer used in the UK for health and safety considerations, although still used in other countries such as middle east (Leach and Pierce, 1999). On this basis, polyurethanes were replaced by amine-cured epoxy systems in the UK, but both these and the polyurethanes are more expensive than UCH150H,which is another attraction of using UCH150H in flexographic inks. The implementation of optical microscopy and scanning electron microscopy confirms that UCH150H had better adhesion on BOPP when incorporated in flexographic ink than Surkopak 5323. The results gained from EDX also confirm that the oxygen content increased by increasing the UCH150H and Surkopak 5323 composition in the flexographic ink printed on BOPP. Application of the tape test confirms that the remaining ink layer on the BOPP surface after applying the test, is the residue of adhered polymer layer which is greater in the case of UCH150H than Surkopak 5323. AFM confirms that the surface of BOPP coated with UCH150H was positively charged and the surface of BOPP coated with Surkopak 5323 was negatively charged. Other techniques such as IR, NMR and ESCA confirm the chemical structure of UCH150H and Surkopak 5323; the presence of un-reacted carboxylic acid in the UCH150H, is found to play an important role in adhesion according to IGC studies. These data suggest that the superior adhesion is the result of interacting acidic groups with BOPP surface by hydrogen bonds, where the basicity increases after adhesion of UCH150H and Surkopak 5323 to BOPP substrate. The flexographic inks prepared by using fumaric rosin UCH150H were tried in many print houses and the results of the print were acceptable, especially the adhesion. On the other hand, the ink was commercially competitive compared to the available flexographic inks in the market, besides, the safety of using fumaric rosin UCH150H for food substrates because of its natural source. It should be noted that flexographic ink preparation, printing substrates, tape test, viscosity measurements, colour density of print, wetting measurements and optical microscopy were done in the lab of ink factory (TOPINKS) in Aleppo-Syria. SEM, thermal analysis, FTIR, particle size testing were done in Leeds University, colour chemistry department. Atomic force microscopy (AFM) was done in Leeds University (Institute of practical science and engineering), ESCA) was done in Leeds University (Physical department), NMR was done in Homs university-Syria and IGC in Aleppo university-Syria.
Supervisor: Lin, Long Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.589147  DOI: Not available
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