Young's Relation
this is Young's Relation
is the surface free energy of the liquid
is the surface free energy of the solid
is the interfacial free energy
is the contact angle
A related equation:
is the reversible interfacial work of adhesion.
and the work of cohesion, 
, within the liquid layer
is shown below:
The spreading coefficient, 
is then defined by:
- All of the above equations describe equilibrium conditions.
- The spreading condition, greater than
zero, requires that is greater
than .
Critical Surface Tension
is the critical surface tension of the solid.
was never defined. On a plot of cos
as a function of the difference minus
, would be the slope.
Notice below how there is a somewhat linear correlation between the
Hildebrande
solubility parameter
and the critical surface tension.
Last Update- January 22, 1995- wld