Classification of Wetting Processes

FIGURE 17.9. Three types of wetting phenomena may occur, each with its own thermodynamic relationship. They are (a) adhesional wetting in which two surfaces make contact displacing a third phase, but without flow (Z ) spreading wetting, similar 

It is clear from Equation (17.15) that for 0 0, 5 cannot be positive or zero, and spontaneous spreading will not occur. 

---