Electrostatic (Thermoset) Powder Coating

PROCOAT Guide: Read about thermoset powder coatings solutions in detail

The principle behind thermoset powder coatings is that the powder coating is formulated by dispersing pigments in a matrix of crosslinkable materials, grinding the materials to a powder, applying the powder to a surface and heating or baking to cause the powder particles to coalesce to form a layer on the surface or allowing curing or crosslinking to take place to form a thermoset layer. Thermosetting powder coatings, having for instance outstanding properties in exterior end applications, are typically based on polyester resins.

Thermoset materials are used for the majority of powder coating processes because they can provide a surface layer that is both durable and decorative. Most thermoset powders have a molecular weight lower than that of thermoplastic materials and higher than that of liquid coatings. Thermosets are solid resins that, when heated, melt, flow, and unlike thermoplastics can crosslink with one another or other reactive substances to form compounds with higher molecular weights. After curing, a thermoset coating remains thermally stable, meaning it cannot be melted back into a liquid from further heating.

In a powder coating system, the more brittle thermoset resins can be broken up into a very fine powder that can then be fabricated into an exceptionally thin, paint-like film. This film exhibits chemical and physical properties comparable to those of liquid-based coatings. In addition, advancements in thermoset technology have continuously increased the versatility of this material group, allowing for more customization options. Many standard thermoset materials can now be chemically altered to provide the specific characteristics required for a given application.

Features & Benefits

The most commonly used thermoset powder coating resins derive from the epoxy, hydroxyl or carboxyl, acrylic, and silicone groups. They generally require lower curing temperatures than thermoplastics, and manufacturers often introduce additives to accelerate or delay the curing reaction. It is important to subject a powder-coated product to thorough heating and allow the thermoset to flow evenly over the targeted surface because once the thermoset powder has completed crosslinking, it cannot be reflowed to correct any flaws in the coating. To achieve successful coating results, it also necessary to match the thermoset formulation with the product’s intended corrosion resistance, curing cycle, texture, and aesthetic properties.

One of the most significant developments in thermoset powder coating involves the capacity to engineer resin types with variable properties designed to complement metal finishing treatments. This broader range of characteristics has led to an increase in specialized roles for thermoset powders, with polyesters and acrylics finding greater use in the automotive and appliance industries despite the traditional reliance on epoxy-based coatings. Most thermoset powders can provide a high level of corrosion, temperature, and impact resistance. They can also be designed with a wide range of colors, glosses, and surface finishes. Coating texture can be wrinkled, smooth, or matte, while film thickness is highly adjustable.

Thermosetting powder coatings based on epoxy and polyester resins designed for interior applications

Polyester Powder Coatings

Gives excellent outside durability and resistance to yellowing. Range of Polyester Powder Coatings is formulated on selected resins and light-fast pigments to give outstanding durability and is designed to customer requirements.

Features & benefits

Polyester Powder Coatings offer good mechanical resistance, including great flexibility and impact resistance, and good chemical resistance.

Application Areas

Agricultural Equipment
Automotive Components
Architectural Cladding
Cookers
Garden Furniture
Heaters
Lawn Mowers
Radiators
Wheels
Window Frames

Epoxy Polyester Powder Coatings

Based on specially selected resins to give the hard durable finish associated with epoxy coating but with superior heat stability and exterior durability.

Typical applications for epoxy polyester powder coatings are those where a tough decorative finish is desirable such as domestic appliances and office furniture. For use requiring ultimate heat stability and outside durability polyester powder should be used.

An epoxy resin crosslinked with a reactive acid polyester will form a blend, or hybrid, material that has flexibility and impact resistance qualities similar to those of other epoxies, but provides a higher level of ultraviolet light protection. These blends are effective when applied as an electrostatic spray and have a range of applications similar to those of thin film epoxies.

Epoxy-polyester powder coatings are supported a mixture of polyester and epoxy resins. The curing schedule is normally 12-15 minutes or 170-180 deg C metal temperature. An acrylic powder is fixed once ornamental needs square measure bigger and extended ultraviolet light resistance is crucial.

Much high-visibility automotive trim and exterior elements square measure coated with polyester and acrylic powder coatings. The analysis unconcealed a negative influence of coating surface texture on coating thickness and consequently a scarcity of barrier and adhesion properties. The epoxy-polyester powder coating showed a far better performance than the polyester coating.