Spreading Coefficient: Compare the Relevant Interfaces

Define the Interface or Transport Basis

KRÜSS defines the spreading coefficient as work of adhesion between the phases minus work of cohesion of the spreading liquid. Under the stated interfacial conditions, a positive coefficient favors complete spreading; a negative value describes incomplete wetting. Identify the spreading phase before applying the subtraction.

Review a Hypothetical Comparison

In a fictional comparison, work of adhesion is 76 mJ/m² and work of cohesion is 58 mJ/m² for one specified liquid pair. Their spreading coefficient is +18 mJ/m². A second pair has the same 76 mJ/m² adhesion term but an 84 mJ/m² cohesion term, giving −8 mJ/m². Choosing only the larger adhesion value would miss the competing cost of creating the spreading liquid's surfaces.

Keep the Evidence with the Decision

Create a phase sketch with the liquid that would spread clearly marked. Record the two work terms with matching area units and their measurement or calculation basis. Recheck the balance if temperature, contamination or composition changes. Observe the actual film formation over the available time rather than treating a positive thermodynamic tendency as a specified spreading speed.

This is a defined interfacial-energy comparison. It is not an antifoam activity rating or a prediction of how long a wet film survives on a particular machine surface.

Does the interfacial-energy balance favor spreading under the defined phase conditions?

This blank worksheet is for your own project. It contains no H M machine trial result.

Customer Questions

Primary References

These references support the technical principles discussed in this guide. The worked examples and review questions are educational.

• KRÜSS defines the spreading coefficient
• Reference from hmpharmamachines.com