Understanding of Transient Adhesion and Anti-Adhesion through Analyzing the Ink Transfer in Planographic Printing
In many engineering applications liquids are forced to contact solid surfaces under highly dynamic conditions with the intention to transfer the liquid onto the solid surface. Examples can be found in food processing, surface coating and printing. Conversely, in many other applications adhesion and transfer of the liquid onto the solid surface are not desirable, but the forced contact of liquid with the solid surface cannot be avoided. Examples can also be found in food processing, printing and some adhesion applications. Traditional approaches to solving these problems are almost invariably based on surface energy, wetting and work of adhesion.
Whilst strong and long lasting adhesion does rely on the surface energy compatibility, work of adhesion and wetting, the transfer of a liquid under dynamic conditions onto a solid surface requires only transient wetting/adhesion under external forces. Phenomena of forced wetting and dewetting cannot be explained by thermodynamic approaches based on surface energy and work of adhesion, since these approaches do not take account of the dynamic nature of the forced wetting and dewetting.
This study uses ink transfer in planographic printing as an example to present our new understanding on the forced wetting and dewetting, adhesion and anti-adhesion of a liquid to a solid surface. Molecular interactions at the liquid-solid interface must be considered and the adhesion strength of the liquid to the solid surface must be quantified and compared with the cohesive strength (in rheological sence) of the liquid.