Forced wetting and dewetting of liquids on solid surfaces and their roles in offset printing

摘要

Forced wetting of a solid by a liquid is one of the most commonly encountered situations in many engineering applications. In this work, aspects and effects of forced wetting and forced dewetting are studied. Concepts of forced wetting and forced dewetting are used to explain the ink transfer principle in offset printing. In many previous studies, interfacial work of adhesion and work of cohesion, as well as interfacial tension, have been used as criteria to predict ink transfer or non-transfer in offset printing. These criteria take no account of the dynamic nature of the printing process and cannot explain some of the basic observations of ink transfer. An alternative approach is taken in this study to take into account the dynamic nature of ink transfer and to consider forced wetting and forced dewetting. Adhesion strength is calculated and used as a criterion to predict whether ink will transfer or not. This work provides a comprehensive explanation of why ink can be transferred onto Teflon, a material that has lower surface free energy than ink, and thus of the principles behind ink transfer in the offset printing process. (C) 2007 Elsevier B.V. All rights reserved.