II. Steady-State Rheological Investigations

Area of Science:

• Colloid and Surface Science
• Rheology
• Polymer Science

Background:

• Depletion flocculation in alkane-in-water emulsions can cause phase separation and a delay before creaming.
• Understanding the rheological properties during this delay period is crucial for characterizing emulsion behavior.

Purpose of the Study:

• To investigate the steady-state viscometry of a 1-bromohexadecane-in-water emulsion with hydroxyethylcellulose.
• To characterize the flow behavior and rheology during the delay period in depletion-flocculated emulsions.
• To attribute structure formation to interdroplet depletion interactions.

Main Methods:

• Steady-state viscometry of 1-bromohexadecane-in-water emulsions with hydroxyethylcellulose.
• Comparison with a related system lacking polymer to isolate effects.
• Analysis of shear-thinning and Newtonian flow behaviors.

Main Results:

• Emulsions with hydroxyethylcellulose exhibited shear-thinning behavior at concentrations conducive to a delay period.
• The continuous phase and emulsions without polymer displayed Newtonian behavior.
• Structure formation influencing rheology was attributed to interdroplet depletion interactions.

Conclusions:

• Interdroplet depletion interactions are the primary drivers of structure formation and rheological changes in these emulsions.
• The concept of dynamic yield stress is relevant for understanding space-spanning phases or transient gels in such systems.