Research Progress on Improving the Stability of Paraffin Emulsion: A Mini-Review

Paraffin emulsion is a highly dispersed thermodynamically unstable system. Emulsifiers play a key role in promoting emulsion formation and improving emulsion stability. However, a single emulsifier has limitations in maintaining emulsion stability, usually, it is necessary to compound more than two emulsifiers or add other additives to make the paraffin emulsion have better stability. Therefore, how to keep paraffin emulsion high dispersibility and stability for a long time are the problems that the majority of researchers have concerned about. This paper expounded the instability mechanism of paraffin wax emulsion, the process of paraffin emulsion destabilization is the process of gradually reducing the free energy of the system, the interaction force between emulsion droplets determines the speed of emulsion destabilization. Sedimentation and stratification, flocculation, coalescence, and Ostwald Ripening were the main factors leading to paraffin instability, the prevention and improvement methods are proposed for the above four mechanisms. And from the instability mechanism, the factors affecting the stability of paraffin emulsion mainly include the mechanical strength and film elasticity of the interface film, the interfacial charge or obstruction between the emulsion droplets, the appropriate system viscosity, and the uniform droplet size distribution will affect the stability of the paraffin emulsion. Through literature research, several methods to improve the stability of paraffin emulsion were summarized, polar paraffin has good emulsifying properties, compounding with paraffin can not only reduce the amount of emulsifier but also enhance the stability of paraffin emulsion, adding thickeners can reduce the Brownian motion of droplets and improve the chemical and mechanical stability of wax emulsions, the addition of ionic surfactants can reduce the diffusion rate of the dispersed phase, the addition of inorganic salts can make the emulsion droplets generate strong repulsion when they are close to each other, and improve the stability of the emulsion, the addition of small molecular alcohols can improve the flexibility of the oil-water interface film properties, reduce the surface tension coefficient of the emulsion, and increase the stability of the paraffin emulsion. This paper can provide a theoretical reference for the research on the stability of paraffin emulsion.