Spreading Coefficient

Definition of Spreading Coefficient

• The spreading coefficient (S) indicates the ability of one liquid to spread over another. It is defined as:

  • • • • • $S = \gamma_S – (\gamma_L + \gamma_{SL})$

• where:
• γS​ is the surface tension of the sublayer liquid.
• γL​ is the surface tension of the spreading liquid.
• γSL​ is the interfacial tension between the two liquids.

Interpretation of Spreading Coefficient

1. Positive SSS: Spreading occurs spontaneously.
2. Negative SSS: No spontaneous spreading.

Applications

1. Topical Formulations: Influences the spreadability of creams and ointments.
2. Coating Processes: Affects film formation on solid surfaces.
3. Emulsion Stability: Determines the ease of emulsification.

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!