In the paint, the resin is dispersed in water as suspended particles. After coating, the water gradually evaporates, the volume of the wet coating film decreases, and the resin particles gradually approach each other and contact each other. If the ambient temperature is higher than the minimum film-forming temperature of the coating , the resin particles have a large deformation ability, and the resin particles can fuse with each other to form a continuous coating film, which is transparent and tough, with high gloss.
The film-forming process of thermoplastic latex paint is shown in the figure below:
The deformability of resin particles is related to the T g temperature of the resin. The T g temperature is high, the deformability is poor, and it is difficult to fuse. In order to make the coating film have higher mechanical properties, the resin should have a higher T g . Adding film-forming aids to latex paint can reduce the T g of the resin during film-forming , so that the paint has a lower film-forming temperature. However, the minimum film-forming temperature of latex coatings is generally about 10°C. If the ambient temperature is lower than or close to minimum film-forming temperature, the resin particles have greater resistance to deformation and are difficult to fuse, resulting in discontinuous coating films that are loose and opaque. , dull.
Ambient humidity has a great influence on the drying property of latex paint. Excessive humidity can inhibit the evaporation of water in the wet coating film; lower humidity or speed up the circulation of air can facilitate the evaporation of water and accelerate the drying speed of the coating film.
Latex paints are fast on the surface (<2 hours), and it takes about 24 hours to dry, and the effective drying time is very long, about 2 weeks. However, due to the fast surface drying, the recoating interval is short.
