Liquid spreading on ink-jet paper evaluated by the hydrodynamic and molecular-kinetic models

The dynamic surface wetting kinetics of sessile water and ethylene glycol droplets deposited on ink-jet papers was studied. The hydrodynamic and molecular-kinetic models were used for data analysis and the results were compared with each other. Hoffman-Tanner plots gave good linear fits with experimental data, but only the low velocity linear data fit correlated well with experimentally determined pseudo-equilibrium contact angles. The molecular-kinetic model gave a good non-linear fit with experimental data and produced physically meaningful values for the molecular parameters. A high rate wetting phase was found for some liquid-paper sample systems, which was correlated to capillary flow in 'micro-crack' surface structures. Deviation in low rate wetting behaviour from the hydrodynamic and molecular-kinetic models cannot solely be explained by surface structure and roughness. Consequently, it can be assumed that surface chemistry has a significant effect on wetting dynamics.