Emulsion Paint

What Is Emulsion Paint?

Emulsion Paint is a paint in which the disadvantages of conventional oil-based and water-based paints are improved by the emulsion technique.

Emulsion paints are non-flammable, and viscosity can be easily adjusted and additives can be easily mixed.

Emulsification is the process of mixing liquids that do not mix with each other, oil-based and water-based components, by dispersing fine particles of one into the other.

Emulsion technology was first used in the U.S. in 1927, when synthetic rubber was successfully produced from butadiene emulsifier dispersion.

Uses of Emulsion Paint

Sixty percent of emulsion paints are used for architectural applications. This is because, compared to oil-based paints, emulsion paints contain less volatile organic compounds and help prevent sick building syndrome. In particular, water-based emulsion paint can be freely diluted with water, and its viscosity can be easily adjusted with a thickening agent, making it suitable for spraying. They are easy to apply even to highly hygroscopic surfaces such as mortar, and pigments and additives can be easily mixed.

Thermosetting acrylic emulsions are used for metal coating. Baking is performed after coating, causing a cross-linking reaction that improves hardness, adhesion, and resistance to water and solvents.

Under harsh conditions, thermosetting acrylic emulsions are sometimes used for metal coating, such as acrylics with excellent weather, water, and alkali resistance. Baking is performed after painting to induce a cross-linking reaction to improve hardness, adhesion, and resistance to water and solvents.

Principle of Emulsion Paint

First, emulsion particles dispersed in water are brought close to each other by the painting process and are packed tightly together. As the water evaporates, the protective layer on the surface of the particles is destroyed, and cross-linking progresses on the exposed polymer surface, gradually resulting in adhesion. The adhered particles form a uniform film, which becomes a pigment-filled coating film.

If the drying temperature is below the minimum film-forming temperature, the particles will not deform and adhere, resulting in a powder that is not strong enough. Therefore, auxiliary agents are added to facilitate the reaction.

Since most emulsions cannot be restored to their original state once frozen, ethylene glycol is added as a freezing stabilizer or copolymerization of hydrophilic monomers is used to stabilize the emulsion. Dispersants, thickeners, stabilizers, and anti-fungal agents are also added as needed to stabilize the quality of the paint during storage.

In addition, the mechanical strength of emulsion paints is often higher after a certain period of time than immediately after the formation of the film, due to the diffusion of the polymer after the film is formed.

Types of Emulsion Paint

Emulsion paints can be broadly classified into oil-based and water-based paints based on their solvents. There are oil-based paints that use organic solvents and water-based paints that use water as the solvent.

Emulsion paint can also be solvent-based or water-based. Paints with water particles floating in an oil-based solvent are called solvent-based paints, while those with oil-based particulate components mixed in a water solution are called water-based paints.

Organic solvents used in oil-based paints can be harmful to the environment and the human body, and manufacturers have focused on improving water-based paints by developing surfactants, substances that stabilize them in an emulsified state. As a result, emulsion paints with oil-based pigments dispersed in them were developed, and water-based emulsion paints are now the mainstream.

How to Select Emulsion Paint

The most important characteristic of emulsion paint is curing. Curing is the process by which the water in the paint evaporates over time to form a hard coating film.

Depending on the method of curing and the strength of the coating film, there are two types of curing: fusion-fusion curing and water-based reaction curing.

Fusion fusion curing is a phenomenon in which dispersed particles come together, fuse, and harden due to evaporation of water or oil. Since the particles themselves are purely fused together, the adhesion of the coating film is relatively weak.

On the other hand, in water-based reaction curing, particles and a reactant mixed with the particles in advance adhere to each other as the water or oil evaporates. This is called a cross-linking reaction. The hardening caused by the cross-linking reaction fuses the three-dimensional structure between the particles, resulting in a stronger paint film.

Water-based reaction-curing emulsion paint containing a reactant is recommended when durability of the paint is required.

Other Information on Emulsion Paint

1. Characteristics of Emulsion Paint

Emulsion Paint is less harmful to the human body. After oil-based paint is applied, the solvent component evaporates and the paint film hardens. If inhaled, the user may feel sick and even lose consciousness. The small amount of solvent residue that remains after drying can cause health problems such as sick building syndrome. Emulsion Paint, on the other hand, does not adversely affect health because of the moisture that evaporates.

However, compared to oil-based paints, the adhesion of the paint film is poor. Since the paint is suspended in water, it is more hydrophilic than oil-based paints, and there is a drawback that the paint tends to peel off in areas exposed to rainwater, such as exterior walls. To compensate for this disadvantage, it is necessary to apply several layers of paint.

2. Paint Grade

Paint grades vary according to durability. Acrylic, urethane, silicone, and fluorine paints are the most durable and expensive, in that order. Of these, silicon paint offers the best balance between durability and price.

Silicon paint is used in many painting projects and is currently the mainstream paint. Acrylic and urethane paints are used when the initial cost is more important than durability.

• • • • Acrylic paint
        The least expensive, extremely low durability, and rarely used for exterior walls.
      • Urethane paint
        Low cost and low durability. Lowest grade of paint used for exterior walls
        • Silicon paint:

        Most cost-effective in terms of price and service life, and currently the mainstream.

      • Flourine Paint
           Longer service life, but more expensive

3. Sick House Syndrome　

Sick house syndrome is a general term for health problems thought to be caused by indoor air pollution from volatile organic compounds contained in building materials and interior materials as houses become more airtight and insulated.