31
Fig. 9.20 SFE calculation for a solid surface using three liquids
The second option ‘Polar/Dispersive’ uses contact angle readings from two selected test liquids to
determine the SFE of a substrate. Here the two first liquid fields (Water and DIM) are activated.
For these calculations, the Harmonic approach (Wu) is used as the first option as this is considered
'more accurate'. This approach can, however, end up in negative roots, so there is not always a solution
to these equations. In this situation the program changes to the Geometric approach (Owens-Wendt),
which always gives a solution. The SFE report indicates which method was eventually used
(Harmonic or Geometric) for the calculation. It is possible to force the Geometric method if the
parameter SFEMETHOD is changed from H to G (see Section 9.18 of this User’s Manual).
The third option ‘Acid/Base’ (Lewis) uses three liquids to calculate the surface energy from an
equation system. Here all three liquid fields are activated (Water, DIM and Formamide).
Please note the calculated results depend on the liquid combination used.
To select an input data file, use the associated Browse button.
For Water, the browse button will present files with a
wgs
extension only as these should contain
results from water contact angles. In a similar way the other two browse buttons (if active) can be used
to select other result files measured with DIM or Formamide. As soon as the result file for Water has
been selected, the first part of the file name is used for the field ‘Sample ID’ (e.g. 45901).
