Water-reducible flexographic printing inks-rheological behaviour and interaction with paper substrates
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/journalofmat_1999.doc |
| Abstract: | SUMMARIES. The rheological behaviour of 5 water-reducible flexographic printing inks was tested using viscometer with the cone and plate geometry. The obtained shear stress versus shear rate curves for the original inks, and additionally, for the mixtures with various amount of added water, exhibit pseudoplastic behaviour, and were successfully fitted by Ostwald and Casson models. The viscosity of printing inks after addition of water was tested also by means of outflow funnel. The transfer of flexographic inks on the different paper substrates was examined by optical density measurements. The density curves confirmed that the ink concentration above 50 wt% is sufficient to obtain the constant value of optical density. The best ink transfer to the investigated paper substrates was observed for folding carton characterized by the high value of smoothness. CONCLUSION. 1. The shear stress versus shear rate curves for the 5 different flexographic printing inks with various amounts of added water were measured and evaluated using Ostwald and Casson models. The fluids exhibited pseu-doplastic flow behaviour. The Ostwald and Casson parameters calculated were significantly dependent on the ink concentration. The rheopectic behaviour of the investigated inks reflect probably the changes in the ink composition by solvent evaporation during measurements. 2. The optical density of the ink films coated on the paper substrates with different characteristics was monitored for the printing inks with various amounts of water. The reduction of ink concentrations up to 50 wt % has no influence on the optical density measured on the paper substrates. However, the viscosity of the 50 wt % yellow ink is too low for the flexographic printing technology. The highest values of optical density agree with the smoothness of the paper substrates. |
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| ISSN: | 0022-2461 |