The food must be without any safety concerns, therefore the role of packaging, materials and printing is to ensure the impermeability of packaging and to limit the migration of components from packaging materials and printing inks. Consequently, the low migration printing inks, which require optimized printing processes compared to the standard printing inks, have become more frequently used lately. The migration of substances from the low migration printing inks from the printed cross-linked surfaces must be within the prescribed limits. The UV-drying flexographic printing inks are intended for printing on flexible food packaging, in our case on heat-shrinkable sleeves.
The purpose of this master's thesis was to analyze properties of printing inks intended for production of food packaging. Two types of printing inks were to be indirectly analyzed through prints with the standard and test low migration printing inks, printed on three polymer films, made of oriented polystyrene (OPS), polyvinyl chloride (PVC) and polyethylene terephthalate (PET), and results to be compared with the declared data and with each other. The aim of the study was to determine the basic, mechanical, surface and optical properties of three unprinted and six printed samples, and to expose them to factors: reagents (weak acid, strong alkali, alcohol and organic solvent) and mechanical rubbing. Images of surfaces were to be captured with optical and SEM microscopy in order to analyze optical properties of the imprinted surfaces.
Results show that the tested polymer films are of good quality, because their basic and mechanical properties are in accordance with the declared ones – suitable tensile strength, rigidity and toughness. The study showed that printing with low migration printing inks has adequate adhesion with polymer films, a very smooth surface, adequate minimal visual and colorimetric differences and a relatively uniform application of printing ink. Reagents, the most influential of which are alcohol and organic solvent, affect all prints, most notably the printed polymer films of polyvinyl chloride. The visual analysis of SEM captured images revealed differences in surface morphology in the form of clusters of pigments and darker areas, suggesting slightly unevenly mixed, distributed or dried printing inks. The polyethylene terephthalate film, printed with low-migration printing inks, has the best features, followed by oriented polystyrene film, whereas only the printing on polyvinyl chloride is of a bit lower quality.
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