Surface Free Energy Calculator

Example Data Table

Illustrative example using water and diiodomethane for a polymer film surface.

Liquid	Contact Angle (°)	Total γ_L	Dispersive γ_L^d	Polar γ_L^p
Water	80.00	72.80	21.80	51.00
Diiodomethane	50.00	50.80	50.80	0.00

Example output: Total surface free energy ≈ 38.92 mN/m.

Dispersive component: ≈ 34.27 mN/m.

Polar component: ≈ 4.64 mN/m.

Formula Used

Owens-Wendt-Rabel-Kaelble model:

γ_L(1 + cosθ) = 2[√(γ_S^dγ_L^d) + √(γ_S^pγ_L^p)]

Using two liquids creates two equations that solve the unknown solid dispersive and polar components.

Total surface free energy: γ_S = γ_S^d + γ_S^p

Young-Dupré work of adhesion: W_A = γ_L(1 + cosθ)

Interfacial tension: γ_SL = γ_S + γ_L - W_A

How to Use This Calculator

Enter a sample name and optional temperature.

Choose two probe liquids with known total, dispersive, and polar tension values.

Type the measured contact angle for each liquid on the same solid surface.

Keep liquid properties consistent so total equals dispersive plus polar.

Optionally add a third liquid to compare measured and model-predicted angle.

Press the calculate button to view solid surface energy components and interpretation.

Use the graph and detailed table for analysis, reporting, and comparison.

Download CSV or PDF output when you need documentation.

Frequently Asked Questions

1) What does surface free energy describe?

It describes how strongly a solid surface interacts with surrounding materials. Higher values usually mean better wetting, stronger spreading, and improved adhesion for coatings, inks, and adhesives.

2) Why are two liquids needed?

The Owens-Wendt method solves two unknowns: the solid dispersive component and the solid polar component. Two different probe liquids provide the two equations required for that solution.

3) Why should the liquids have different properties?

Liquids with clearly different polar and dispersive behavior improve numerical stability. A polar liquid like water and a mostly dispersive liquid like diiodomethane are a common pair.

4) What happens if the contact angle is very high?

A high contact angle usually signals weaker wetting and a lower effective interaction between the liquid and the surface. That often points to lower coating friendliness or more hydrophobic behavior.

5) Why can the calculator show a non-physical solution?

That usually means the contact angles, liquid properties, or pair of liquids do not fit the model well. Recheck measurements, units, and liquid component values before interpreting the result.

6) What is the purpose of the third liquid?

The optional third liquid works as a validation check. The calculator predicts its contact angle from the solved surface energy and compares prediction against your measured value.

7) Are the results affected by roughness or contamination?

Yes. Roughness, chemical contamination, surface aging, and inconsistent droplet placement can change contact angle readings. Clean, uniform, and reproducible surfaces produce more dependable estimates.

8) Which units are used here?

Surface tension, interfacial tension, work of adhesion, and surface free energy are shown in mN/m. Contact angles are shown in degrees throughout the calculator and report output.