Powder Coating Definition
Powder coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a “skin”. The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as household appliances, aluminium extrusions, and automobile and bicycle parts. Newer technologies allow other materials, such as MDF (medium-density fibreboard), to be powder coated using different methods.
PROPERTIES OF POLYESTER POWDER COATING
Polyester powder coatings exhibit excellent flexibility and durability with very good outdoor (UV) resistance. They represent approximately 50% of all powders used in North America today. Polyester provides smooth, thin coatings in a full range of glosses, from very high gloss (90%) to very low gloss (5%).
Polyester powder coating is designed to produce thin film coatings in the range of 1 to 4 mils and are applied by the electrostatic cold powder spray method.
Typical polyester applications include outdoor furniture, lawn and garden equipment, automobile aluminum wheels, appliance exteriors (ranges, refrigerators, etc.), outdoor transformers, architectural aluminum extrusions, fluorescent lighting fixtures, playground equipment, and air conditioners.
EPOXY POWDER COATING – PROPERTIES OF
Epoxy powder coating is a thermosetting material, applied by electrostatic spray, fluidized bed, and hot flocking. It offers the best chemical and corrosion resistance. It is used in the coating of gas and oil pipe, which are buried and cathodically protected against underground galvanic corrosion.
Epoxy provides excellent protection in these environments but have other limitations, primarily its poor resistance to ultraviolet (UV) radiation. When exposed to sunlight or other UV radiation, it “chalks”. This is a milky or chalky surface condition, which in many cases can be removed by washing or polishing. It reforms rapidly, however, and presents an aesthetic problem.
Epoxy powders are also designed to serve as decorative as well as functional coatings with a wide variety of colors.
Epoxy powder applied cold by electrostatic spray produce thin films of 1 to 4 mils. Thick films of 10 to 20 mils can be achieved by heating the part to be coated and fluid bed coat (dip), hot flock spray, or electrostatic spray.
Other typical applications include automotive accessories and underbody, metal cabinetry, power tools, sports equipment, electrical apparatus and framework, light fixtures, indoor furniture, metal shelving, and wire goods.
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