With the change of the weather, and the early summer season is coming, the problem of whitening of the paint film began to show up again! So, what are the reasons for the whitening of the paint film? There are four main aspects: the moisture content of the substrate, the construction environment, and the construction. Process and coatings.

First, the substrate moisture content

1. Changes in moisture content of the substrate during transportation

The drying time of the paint film is short, the evaporation of water takes a long time, the moisture in the veneer can not overflow the paint film due to the blockage of the paint film, and the water will accumulate to a certain amount, and the difference in the refractive index of the water and the refractive index of the paint film is caused. The paint film is white.

2. Changes in moisture content of the substrate during storage

After the paint is formed to form a paint film, the moisture in the substrate is gradually precipitated, and a micro sac is formed in the paint film or between the paint film and the substrate to make the paint film white.

Second, the construction environment

1. Climate environment

In high temperature environment, the heat absorption caused by the rapid evaporation of the diluent during the coating process may cause the water vapor in the air to condense into the paint and make the paint film white; in the high humidity environment, the water molecules will adhere to the surface of the paint. After the spraying, the water volatilizes, causing the film to fog and whitish.

2. Location of the factory

Different plants are in different zones. If they are close to the water source, the water will evaporate into the air to make the water vapor content in the atmosphere large, which will cause the paint film to be white.

Third, the construction process

1, fingerprints and perspiration

In actual production, in order to improve production efficiency, workers do not wait for the paint to dry after spraying the primer or topcoat. If the worker does not wear gloves, the contact with the paint board will leave a mark, which will result in whitening of the paint.

2. The air compressor is not drained regularly

The air compressor is not drained regularly, or the oil-water separator malfunctions, and moisture is introduced into the paint, causing whitening. According to repeated observations, this blush is produced immediately, and the whitish condition disappears after the paint film is dried.

3, the spray is too thick

The thickness of each primer and top coat is counted in “ten”. One-time painting is too thick, and not more than two or more “ten” characters are applied in strict accordance with the regulations, resulting in inconsistent solvent evaporation rate of the inner and outer layers of the paint film, resulting in uneven film formation of the paint film, and the transparency of the paint film is poor and white. An excessively thick wet film also prolongs the drying time, thereby absorbing the moisture in the air to cause the coating film to blister.

4, improper adjustment of paint viscosity

When the viscosity is too low, the paint layer is thin, the hiding power is poor, the protection is weak, and the surface is easily damaged by corrosion. If the viscosity is too high, the leveling property may be poor and the film thickness may not be easily controlled.

5, the water coloring agent causes the paint film to whitish

The commonly used coloring agent is water-based, and the drying time is not up to 4 hours after finishing, that is, other spraying is performed. After drying, the residual moisture will form a tiny sac between the paint film and the paint film with the extension of time, and the paint film will gradually appear white and even white.

6, to be dry environment control

The space to be dried is large, the sealing is not good, and the temperature of the air conditioner inside is difficult to maintain at 25 °C, which may lead to whitish product. In some areas of the dry house, there is direct sunlight, which promotes the absorption of ultraviolet light by the wood, thereby accelerating the photodegradation of the wood surface, which easily leads to whitish product.

Fourth, the problem of the paint itself

1, thinner

Some diluents have a relatively low boiling point, and the volatilization is too fast. The instantaneous temperature drop is too fast, and the water vapor condenses into the surface of the paint film and is incompatible and white.

When the diluent is not used, there is a substance such as acid or alkali remaining, which will corrode the paint film and become white over time. The diluent has insufficient dissolving power to cause the paint resin to precipitate and become white.

2, wetting agent

The difference between the refractive index of the air and the refractive index of the powder in the paint is much larger than the difference between the refractive index of the resin and the refractive index of the powder, causing the paint film to be white. Insufficient amount of wetting agent will cause uneven accumulation of powder in the paint and whitening of the paint film.

3. Resin

The resin contains a low-melting component, and these low-melting components are precipitated in the form of amorphous microcrystals or microscopic sacs at a low temperature.

Solution summary:

1, the substrate moisture content note

Furniture companies should use a special drying equipment and drying process to strictly control the equilibrium moisture content of the substrate.

2, the construction environment pay attention to

Effectively control the temperature and humidity, improve the construction environment, stop the spraying operation when the wet temperature is too high, avoid the humidity of the product in the spraying area is too high, the dry area is illuminated by sunlight, and the whitish phenomenon is found to be corrected in time after construction.

3. Points to pay attention to during construction

The operator should wear a book cover, can not cut corners, can not carry the film when the film is not dry, the paint should be strictly in accordance with the ratio of ingredients, the time between two recoating can not be shorter than the specified time, follow the “thin and many times” the rules.

When working with an air compressor, if the paint film is found to be whitish, take immediate measures to stop the spray operation and check the air compressor.

4, the use of paint points of attention

The diluent should be used together to adjust the amount of diluent added and the amount of wetting and dispersing agent.