Influence of Fluid Rheology on Filament Size, 2000 International Printing & Graphic Arts Conference Proceedings

Saybil N. Ercan, Douglas W. Bousfield--During roll coating or printing, filaments are produced at the nip exit if the operational speeds are large enough. The size of these filaments influence issues such as misting, leveling of filaments, and ink gloss development. Filaments of model fluids and inks are recorded with a high-speed video camera with a high magnification lens to visualize the exit of the nip on a roll system. One roll is made of a clear material to allow more light into the nip. The average filament volume and volume distribution are reported as a function of film thickness and fluid type. A simple procedure to test the tensile forces of the fluids was developed and evaluated. Fluids with similar rheological properties showed quite different filamentation behavior. The tensile behavior of the fluids did correlate with filament size, but the model inks had the opposite trend compared to the pick test oils and silicon oils. In general, fluids that have an elastic behavior tend to generate smaller filaments. This behavior may be due to a fracture behavior of the fluid in contrast to a viscous film split.