Understanding phase inversion in resin emulsification

Creating a stable resin emulsion requires more than simply combining resin and water. The emulsification process, the energy applied and the selection of the right emulsifier can all influence the properties and stability of the resulting emulsion.

In this article, we take a closer look at phase inversion and the role emulsifiers play in helping create stable, finely dispersed resin emulsions.

What is resin emulsification?

An emulsion combines two phases that would not ordinarily remain mixed, such as resin and water.

Preparing an emulsion requires a combination of mechanical and thermal energy and, in many cases, an emulsifier.

Emulsifiers are surface-active agents that migrate to the resin-water interface, where they reduce the interfacial tension between the two phases. Lowering this tension helps create smaller emulsion droplets, contributing to improved long-term stability.

Why is emulsifier selection important?

Choosing the right surfactant is an important part of resin emulsification.

The surfactant influences the properties of the resulting emulsion and whether a stable emulsion can be achieved. For resin emulsification, this means finding the appropriate balance between hydrophilic and hydrophobic characteristics.

Different resin systems and formulation requirements can therefore require different emulsifier approaches.

How does phase inversion work?

In the phase inversion method, the emulsifiers are first dissolved in the oil or resin phase.

Water is then slowly added under constant stirring. Initially, this creates a water-in-oil emulsion.

As additional water is introduced and the inversion point approaches, the viscosity increases. This change can be monitored through the torque required during stirring.

With continued water addition, the emulsion spontaneously inverts from a water-in-oil emulsion to an oil-in-water emulsion.

At phase inversion , viscosity dramatically increases, and then once passed, the viscosity drops again.

Further water can then be added to control the final solids content of the emulsion.

Once cooled to ambient temperature, the resulting emulsion can be easily dispersed in water, with small droplets remaining finely and evenly dispersed.