Investigation Into the Scale-Up of Polymeric Inkjet Inks From Research to Industry

This thesis examines the issues that are involved in taking an ink from the research environment of the laboratory to the production focus of an industrial shopfloor. It starts with two chapters which investigate and evaluate printability. The classical method of determining printability via the Z number was found to be often incorrect, due to it being unable to take account for all the variables that influence printability. Internal properties, such as viscosity, are assumed by many classic printability predictions to stay constant. However, the high stress applied to non-Newtonian inks during inkjet printing can cause properties to change as the ink is ejected. Therefore, the study of the rheology of non-Newtonian inks in an environment similar to inkjet printers is a critical step in predicting an ink’s printability. The external printing conditions include factors such as printhead geometry, waveform design, ink supply system, and nozzle diameter. Every print system has its own set of printing conditions, which make it impossible for an ink to be printable with all printers. The difference in printing conditions is especially apparent when the scale of work is changed from small-scale research printers to large-scale industrial print systems. This thesis then took this understanding of the importance of rheology and printing conditions and applied it in three independent case studies. The three case studies highlighted the difficulties associated with up-scaling inkjet inks from forgiving small-scale lab printers to complex and specialised industrial printers. This thesis shows by evaluating the high frequency rheology of inks, and using industrial printheads in research settings, it is easier to predict the behaviour of an ink during ejection and determine printing conditions the ink will be most compatible with. Thus, helping to ease the up-scaling process and providing promising inkjet research a clearer avenue towards commercialization