Acrylic binders for paints and coatings are supplied both in solvent and water. Waterborne acrylic polymers are the binders (or resins) used in the manufacture of waterborne acrylic coatings, also known as acrylic latex coatings. They are solid, plastic-like synthetic materials that are dispersed as microscopic particles in water. The dispersion is a milky-white liquid called a “latex” because it is reminiscent of natural latex from the rubber tree. The polymer particles can be various shapes, but are usually spherical, as shown in the picture below of a freeze-dried sample. The particles are extremely small, with diameters typically in the range of 50 to 500 nanometers.

The process by which a waterborne acrylic coating forms a film is quite different than that of a solventborne coating. When the liquid (mostly water) in the acrylic paint evaporates, the microscopic particles of latex binder and pigment that remain on the painted surface come closer together. As the last vestiges of liquid evaporate, capillary action draws the binder particles together, causing them to fuse and bind the pigment into a continuous, flexible film that will be water resistant when dry. This process of film formation is called coalescence.

Image of a freeze-dried acrylic latex polymer, taken with a scanning electron microscope. These particles are approximately 250 nanometers in diameter.

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