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Wax emulsions are stable mixtures of one or more waxes in water. Waxes and water are normally immiscible but can be brought together stably by the use of surfactants and a clever preparation process. Strictly speaking a wax emulsion should be called a wax dispersion since the wax is solid at room temperature. However, because the preparation takes place above the melting point of the wax, the actual process is called emulsification, hence the name wax emulsion. In praxis, wax dispersion is used for solvent based systems.
A wide range of emulsions based on different waxes and blends thereof are available, depending on the final application. Waxes that are found in wax emulsions can be of natural or synthetic origin. Common non-fossil natural waxes are carnaubawax, beeswax, candelilla wax or ricebran wax. Paraffin, microcrystalline and montanwax are the most used fossil natural waxes that are found in emulsions. Synthetic waxes that are used include (oxidised) LDPE and HDPE, maleic anhydride grafted polypropylene and Fischer-Tropsch waxes.
A range of different emulsifiers or surfactants are used to emulsify waxes. These can be anionic, cationic or non-ionic in nature. The most common however are fatty alcohol ethoxylates as non-ionic surfactants due to their superb stability against hard water, pH-shock and electrolytes. Some applications demand different emulsifier systems for example anionic surfactants for better hydrophobicity or cationic surfactants for better adhesion to certain materials like textile fibers.