3.3.1. Preparation of Emulsions

Mix 2.5 g DMOB emulsifier and 100 mL Skylan No. 5 white oil. Then, add 100 mL of deionized water. Stir at a speed of 12,000 r/min for 10 min to form the initial W/O emulsion. This is labeled as a Type I emulsion.

Take 100 mL of Type I emulsion for each group and add different concentrations (0.60 vol.%) of hydrochloric acid with a concentration of 5.00 wt.% (5.00 vol.%). Stir at 12,000 r/min for 5 min. The prepared W/O emulsion is labeled as a type II emulsion.

Due to the rapid phase inversion process of reversible emulsions, it is difficult to study the phase inversion process by controlling stirring times. After the addition of acid/alkali to the emulsion, except for the point of acid/alkali addition, the rest of the emulsion system experiences a rapid increase in acid/alkali concentration with increasing stirring time. Therefore, the change in the reversible emulsion with the increase in the amount of acid/alkali was used to characterize the phase transition process of the reversible emulsion.

Parallel experiments were conducted for different groups. In each group, 100 mL of Type II emulsion was taken, and different volumes of NaOH solution with a concentration of 5 wt.% (ranging from 0 to 5 vol.%) were added to the emulsions. The mixtures were stirred at 12,000 rpm for a certain time. The emulsion breaking voltage, conductivity, static stability, pH value, dispersed droplet morphology, viscosity, rheological properties, and particle size distribution of each group of emulsions were also tested.

The NaOH solution mentioned in this study refers to a 5% (mass fraction) NaOH aqueous solution prepared by mixing NaOH with deionized water.