Work of adhesion
The work of adhesion W12 is the work which must be done to separate two adjacent phases 1 and 2 of a liquid-liquid or liquid-solid phase boundary from one another. Conversely, it is the energy which is released in the process of wetting. The units of work of adhesion are J/m2.
Background
When one phase is wetted by another, the two previously existing surfaces disappear, as a result of which energy is released due to the respective surface tensions σ1 and σ2. At the same time, work, which is referred to as interfacial tension ;σ12, must be done in order to form the interface. The work of adhesion is given by the following equation:
; For a liquid-solid phase boundary, the work of adhesion ;Wls (l for liquid; s for solid) can be calculated from the contact angle ;θ using the Young-Dupré equation:
The work of adhesion is a measure of the strength of the contact between two phases. Its knowledge is therefore important for processes such as coating, painting, cleaning, printing, hydrophobic or hydrophilic coating, bonding, dispersion etc.
