The curing oven is one of the indispensable equipments in the powder coating production line. The function of the curing furnace determines the quality of the produced workpiece.
The process of coating a substrate onto the surface of a substrate to convert from a liquid or loose solid powder state to a dense, intact solid film, known as drying or curing of the coating or coating.
A: Classification of coatings according to their curing mechanism:
1 non-transformation type (depending on physical action film formation):
1. Volatile paint: The table below is dry at normal temperature, and more natural drying or forced drying at low temperature is adopted.
2. Latex paint: Generally dry in 2 hours, dry for about 24 hours, dry for 2 weeks.
3. Hot melt coating: It needs to be heated above the melting temperature.
2: Transformation type (by chemical reaction, the small molecule is crosslinked into a polymer to form a film)
Generally, heating and drying are required.
Two: common curing methods for coatings
1: natural drying
Under natural conditions, the solvent is evaporated by air convection, oxidative polymerization or reaction with a curing agent to form a film. It is suitable for self-drying coatings such as volatile coatings, air-drying coatings and curing agent curing coatings. The drying quality is affected by environmental conditions. Big.
According to the drying temperature, it can be divided into low temperature drying (less than 100 ° C, mainly for drying the surface coating of self-drying paint or poor heat resistance material). Dry at medium temperature (100-150 ° C, mainly used for condensation polymerization to form a coating for film formation). High temperature drying (above 150 ° C, mainly used for powder coatings, electrophoretic coatings, etc.). According to the heat curing method, it can be divided into:
1. Hot air convection: and hot air convection plus radiation and other methods. The hot air convection heating is uniform and the temperature control is high. It is suitable for high-quality coatings, and is not affected by the shape and structure complexity of the workpiece, but the heating rate is slow, the thermal efficiency is low, the equipment is huge, and the coating is easy to foam and wrinkle. The heat sources used are steam, electricity, diesel, gas, liquefied gas and natural gas.
2. Thermal far-infrared radiation method: The heat radiation heating usually uses infrared rays to heat the substrate and the coating at the same time, the heating rate is fast, the heat efficiency is high, the floor space is small, but the temperature is not easy to be uniform.
3. Hot air convection plus radiation combination method: generally convection after radiation, using the advantages of fast radiation heating, heating the workpiece, and then using hot air convection insulation to ensure the drying quality.
3: Radiation curing
The use of electron beams, ultraviolet radiation electron beam curing coatings and UV coatings has the advantages of short time, solidification at room temperature, and relatively low price of the device. However, there are blind spots in the illumination, and only the workpiece with a simple shape is used, and the irradiation distance is strictly controlled.
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