The stability of powder coating refers to whether the powder will agglomerate in storage or use, the leveling property will become worse, the electrification effect will become worse, the orange grain of the coating film is obvious, the luster will become weaker, the occurrence of pinhole bubbles and so on.

In the trial production of powder coating, we must pay attention to the stability of its storage, only with a certain stability of powder coating, which can let users use.

The stability of powder coating is determined by measuring the leveling property of powder coating at a certain temperature and after treatment for a certain period of time. Because the stability of powder coating indicates the degree of cross-linking reaction in powder coating under storage conditions. The more intense the crosslinking reaction occurs, the larger the molecular weight of the powder, which is reflected in the increase of the viscosity of the powder at the curing temperature and the deterioration of the leveling property.

For powder electrostatic spraying process, the key to consider is the powder coating particles accept charge, maintain charge and charge distribution, which directly affects the powder on the workpiece adsorption and deposition efficiency, in addition, it is important that the uncured powder coating must withstand the mechanical vibration of the transmission mechanism without powder. In fact, the influence of powder particle charge and keep the charge of the main factors of dielectric constant is powder coating, powder, the lower the dielectric constant of electrically charged particles more easily, but the loss of charge is easy, it reflects the adsorption force of powder on the parts not firm, off powder, slightly affected by vibration for electrostatic spraying of powder coatings, should as far as possible with high dielectric constant, it will make powder adsorption capacity is greatly increased. The coating is more uniform. However, it is difficult to charge powder coating with high dielectric constant, so it is necessary to improve the structure of electrostatic powder gun and adopt the structure of multi-electrode forced charge.

For powder coatings, it is composed of polymer compounds (such as epoxy powder, polyester powder, etc.), their adsorption on the workpiece mainly has two: coulomb force (electrostatic force) and molecular force. Polymer compounds have high resistivity, so the coulomb force (electrostatic force) is large and reliable. The electrical resistivity of the powder will determine the charged state of the powder under a certain electrostatic field strength. For example, when the resistivity of the powder is 1013 ohms, the electrostatic voltage is only 30-50kv, and the powder can be charged well. However, when the resistivity of the powder is 108-109 ohms, 100-120 kv electrostatic voltage should be applied to obtain the above electrification effect. The relationship between powder resistivity and electrostatic voltage. Whether the thickness of powder deposition can be automatically limited is closely related to the resistivity of the powder itself. The experiment proves that only the powder with high resistivity can get a suitable coating film.

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