When working with any polymer, if the material surface energy is relatively low, then any coating will not flow well and fisheyes, pinholes, gaps, or air bubbles will form. If the material surface energy is too high, then the paint, ink, or coating may bleed or be difficult to control. Therefore, the surface tension of the liquid and the surface energy of the material must be matched for the application.
The dynamics of wetting (watch video) are described below:
Spreading = A - ( B + C )
- A = surface energy of solid (given below)
- B = surface tension of liquid
- C = surface energy of solid-liquid interface
If Spreading is:
- Negative. Then, liquid will bead up.
- Zero to Postive. Then, liquid will spread.