Interfacial Rheology as a Tool to Characterize the Dynamics of Spontaneous Emulsification

Area of Science:

• Colloid and Surface Science
• Materials Science
• Physical Chemistry

Background:

• Water-in-oil emulsions are vital across industries.
• Spontaneous emulsification can occur with high oil-soluble surfactant concentrations.
• This process involves water droplet fragmentation and interfacial network formation.

Purpose of the Study:

• To investigate spontaneous emulsification in a water/Span 80-paraffin oil system.
• To measure interfacial shear elasticity and observe droplet dynamics.
• To understand the factors influencing network formation and interfacial properties.

Main Methods:

• Utilized a water/Span 80-paraffin oil system.
• Measured interfacial shear elasticity.
• Employed microscopy to capture emulsion dynamics.

Main Results:

• Network formation time depends on contact time and Span 80 concentration.
• Interfacial elasticity exhibits oscillatory behavior at higher Span 80 concentrations due to multilayer droplet formation.
• Increased oil viscosity reduced emulsification rate and elasticity peak.
• Silicone oil and salt addition suppressed spontaneous emulsification.
• Tween 80 addition increased emulsification rate but weakened the network.

Conclusions:

• Spontaneous emulsification is influenced by surfactant concentration, oil viscosity, and oil type.
• Multilayer droplet formation at the interface leads to complex interfacial elasticity trends.
• The study provides insights into controlling emulsion properties through formulation.