Key Points of Automotive Plastic Paint Spraying Technology

For automotive plastic parts coating, interior part focuses on solvent resistance, exterior part focuses on water resistance, stone strike resistance, weather resistance and decoration. Manual air spraying and automatic spraying can be used for plastic parts.

air This method of plastic paint utilization rate is generally about 50% - 60%. The specific process of manual spraying automotive plastic paint is as follows:

1、 Primer spraying
The wind speed in the manual spraying area of the spray booth is generally set at 0.4 ~ 0.5m/s, and the process temperature is generally controlled at 18 ~ 350 ℃. In winter, the temperature of the spray booth is not lower than 180 ℃, but in summer, the highest temperature sometimes reaches about 400 ℃ because the air conditioning unit has no refrigeration system. After the modification of air conditioning system and the addition of humidification system, the temperature in summer can be controlled below 350 ℃ and the relative humidity is generally controlled at 60 ~ 70%.
2、 Primer drying
After the primer is sprayed, the wet plastic film contains a lot of organic solvents. If it is baked directly in the oven, the rapid volatilization of the solvent will lead to pinholes, bubbles and other defects on the surface of the film. In the drying process, with the evaporation of the solvent, the plastic paint can be fully leveled and spread. Drying time and wind speed have great influence on leveling effect. Improper control can easily lead to poor leveling, orange peel and other film defects. The drying time is generally controlled at 5 ~ 7 min.
3、 Primer drying
The primer coating for plastic parts is a two-component coating. At present, there are two kinds of plastic paint: quick drying type and ordinary type. The quick drying type can be dried naturally, but the common type can not be cured naturally and quickly after construction, so the heating curing method is needed. The purpose is to shorten the drying time and improve the performance of the coating. At the same time, considering the heat resistance and deformability of plastic parts, the drying temperature should not be too high, generally controlled at about 800 ℃, and the processing time is generally 20 ~ 30 minutes.
4、 Primer grinding
There are more or less paint defects on the primer surface. In order to provide a good plastic paint coating surface for the next process, it is necessary to polish the primer surface. The polishing material is usually 1000 water sandpaper. When grinding large defects, first rough grinding with 400 sandpaper, then fine grinding with 1000 sandpaper.
5、 Topcoat spraying
Wet spraying process is adopted for the top coat. The primer is sprayed first and then the varnish is sprayed. The primer adopts one component paint, and the spraying thickness of color paint is controlled according to different paint types. Metal paint is generally 12 ~ 18um, plain paint is generally 25 ~ 35um. Spraying process parameters are the same as primer. After spraying, the primer usually dries for 5 to 7 minutes before entering the varnish spraying room. Before spraying, the particles or tiny defects on the paint surface can be polished with No. 1200 polishing pad. After grinding and leveling, the repaired parts can be sprayed with color paint with air paint gun. After treatment, the varnish can be sprayed again.