The role of diluents in epoxy coatings

- Jan 26, 2020-

Diluent is a kind of liquid substance which has good miscibility with resin in order to reduce the viscosity of resin and improve its process performance.

There are active diluents and inactive diluents.

The non-active diluents often added in epoxy resin coating are acetone, methyl-ethanone, cyclohexanone, benzene, toluene, xylene, n-butanol, styrene, etc.


Epoxy coating composition is different, the diluent used is also different, even if the same coating, because of the different seasonal climate, the composition of its diluent is also different, such as in summer, paint with diluent is adjusted to dry more slowly, and winter, paint with diluent will adjust slightly for quick drying.

Therefore, the summer diluent products should not be used in winter, otherwise, because of the slow dry and bring the bottom bite and other paint film defects.


However, the diluent with poor quality not only seriously affects the health of construction personnel, but also easily causes the following paint film morbidity:


1. Poor covering power: the film is too thick and the color of the lower surface can be seen through the paint film.


2, loss of light: the paint film before drying luster fullness, dry lack of luster or after the paint film gradually disappeared.


3. Orange peel: the surface of the paint film is uneven, similar to the appearance of orange peel and grapefruit peel.


4. Cloud/spot (small spot of silver powder paint) : the color of silver powder paint changes to form patches or dark or light spots, often forming different color stripes along the direction of the paint.


5, pinhole (hole) : coating in the coating due to diluent rapid volatilization, make paint fluid too late to replenish, and produce pinhole holes or like the phenomenon of leather pores.


6. Prickly heat (solvent bubble) : because diluent volatilizes too fast, water vapor penetrates into the paint film, causing the top paint to present vesicles and bubble marks.


7. Blurred/foggy: the paint film surface appears milky mist.


8, drip, sag, tears: in the process of coating drying, the excessive paint on the vertical surface from up to down or thickening of the film under the phenomenon.


Therefore, the correct choice of matching diluent, not only can make the paint film has a good appearance, and because of its volatilization rate and paint match, can ensure the paint film appearance effect after painting, and avoid some defects caused by the construction.