The powder coating for electrostatic spraying needs to pay attention to the following several parameters in order to ensure the smooth implementation of the electrostatic spraying process and obtain a high-performance coating film.
The significant difference between powder coatings and solvent-based coatings is the dispersion medium. In solvent-based coatings, organic solvents are used as the dispersion medium; but in powder coatings, use the purified compressed air . The powder coating is in a dispersed state during spraying and cannot adjust the particle size of the coating.
1, powder coating particle fineness
For the powder electrostatic spraying process, the key point to consider is that the powder coating particles receive electric charge, maintain the charge and the charge distribution of charge, which directly affects the power of the powder on the workpiece adsorption and deposition efficiency, in addition, it is important that the uncured powder coating The layer must withstand the mechanical vibration of the conveying mechanism without falling powder.
In fact, the main factor affecting the charge and charge retention of the powder particles is the dielectric constant of the powder coating. The lower the dielectric constant of the powder, the easier it is to charge the particles, also easier to lose the charge. This reflects the absorption of the powder on the workpiece. The adhesive force is not strong, and the powder is powdered by vibration. For electrostatic spraying powder coatings, high dielectric constant should be used as much as possible, which will greatly increase the power of powder adsorption.
2.The resistivity and dielectric constant of powder coatings
The hygroscopicity (moisture content) of the powder coating itself directly affects the self-resistance dielectric constant of the powder. If the powder is heavily hygroscopic, it will be clumped. This cannot be electrostatically sprayed. The general moisture absorption, in addition to affecting its charging performance, will also reduce the powder's fluidity and film formation, so that the coating film is not smooth or even difficult to adsorb on the workpiece and the coating film will produce bubbles and pinholes.
The moisture absorption of powder coating is not related to the preservation and storage, but also related to the degree of compressed air purification during spraying.
3, The water content of powder coating
The stability of powder coating refers to whether the powder will agglomerate during storage or use, the leveling characteristics and the charging effect will be worse, the orange pattern of coating film will be obvious, the gloss will be weakened, and the pinhole bubbles will occur.