Coating: Powder-based

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Description

Note: this record is in progress:

A thermosetting resin preparation used to evenly coat metallic pieces without the use of solvents. Powder coatings were invented and patented in 1945 by Daniel Gustin. However its use only became popular when solvents were tightly restricted at the end of the twentieth century. Electrodeposition is used to uniformly coat a metal object with the finely ground resin, then the metal is baked in an oven to fuse the particles into a hard, resistant film. The coatings are typically 1-3 mm thick. It has been widely used on household appliance, automobiles arts and bicycle frames.

The expanded interest as well as technological advancements in powder coatings has resulted in the use of many types of materials. The most popular are thermosetting resins which are low molecular weight starting resins that, when heated will flow and chemically react to form higher molecular weight final product. This final product is a highly durable resin that cannot be converted back to its initial form. The other advantages of thermosetting resins are that they easily form fine dispensable powders that form thin, paint-like coatings. Specifics for these polymers are given in the table found below.

A second type of powder coatings is composed of thermoplastic resins. This family consists of polymers that will melt with heat then cool back into a solid without any chemical change, i.e. the coating will have the same properties as the starting material. However these resins tend to be difficult to grind into particles that are small enough for spray applications and they have high melt viscosities. thus they are used when a thick film is needed and are often applied using fluidized bed technique. Some of these polymers are, polyethylene, polypropylene, nylon, and polyvinyl chloride. Most often these polymers are used as paints or heat-activated coatings rather than powder coatings.

A third type is the use of inorganic, vitreous coatings. These porcelain or enamel coatings are made by fusing powdered glass onto the metal. They are stable to over 450 C, colorfast and scratch resistant. Applications include coating bathtubs and washing machines.

Table of Properties for Thermosetting Powder Coatings

Polymer type Description Key Weaknesses Temp for cure/time Applications
Epoxy Most commonly used thermosetting powder; wide range of formulations; very high corrosion and chemical resistance; exceptional hardness and adhesion Poor UV resistance; yellows and chalks outdoors. 250 C for 3 min; 120 C for 30 min Indoor industrial parts, underground pipelines, under-the-hood automotive; furniture
Epoxy polyester hybrid Softer, less likely to chip; slightly better outdoor resilience than straight epoxies; have lower hardness and less resistant to solvent Not suitable for harsh chemical environments or prolonged sun exposure. 250 C for 3 min; 180 C for 10 min; 165 C for 25 min Office furniture, household appliances, cabinets; children's toys.
Polyester (Standard) Excellent UV stability, good weatherability, strong mechanical flexibility. Inferior chemical and solvent resistance compared to epoxies. 180 C for 10 min Outdoor furniture, fencing, architectural facades, bicycle frames
TGIC polyester Contain a polyester resin crossllinked with triglycidyl isocyanurate (TGIC); offer very good mechanical properties, impact strength and weather resistant. TGIC formulations can pose minor toxicity concerns during manufacturing. 205 C for 7 min; 155 C for 20 min Standard agricultural equipment, playground equipment, and outdoor cabinetry.
Polyurethane (ester type) Polyester hydroxyl resin cross-linked with blocked isocyanate hardener; outstanding film appearance and toughness as well as good weathering Can outgas if applied too thickly. 205 C for 7 min; 175 C for 17 min Automotive parts; electronic housings;sports equipment; decorative parts
Acrylic Outstanding UV stability, exceptional surface flow, optical clarity. Incompatible with certain chemical compounds and sensitive to substrate preparation Clear topcoats over base layers, high-end appliance parts, and automotive clears.
Acrylic urethane Acrylic resins cross-linked with blocked isocyantates; excellent color, gloss, hardness, weatherability, chemical resistant; less flexible than polyesters Less flexible than polyesters 205 C for 7 min; 182 C for 25 min
Fluoropolymer (FEVE) Premium weatherability, corrosion resistance and color retention High cost, requires specific curing temperature 250 C for 3 min; 120 C for 30 min Monumental architecture, high -rise curtain walls

Commercial Products

The following names for commercially available Powder Coatings were pulled from the AIC Materials Testing page (search for coating and powder)

  • Axalta Coating Systems: Plascoat PPA 571 ES Natural 001 (2020)
  • Prismatic Powders: Polyester Top Coat P-5000 Series (2020)
  • TIGER Drylac: Drylac 049/11350 White Matte MT/SM (2020)
  • Europolveri: Ral 9005/Powdercoat (textured) On Steel (2016)
  • Akzo Nobel: Interpol Powdercoat Paint 3002 (2010); Interpol Powdercoat Paint 9005 (2010); Interpon 200 Powder Coating (2020); Interpon D1036 Textura Powder Coating (ral 9004) (2020); Interpon D1036 Textura Powder Coating (ral 9005) (2020); Interpon D1036 Textura Powder Coating (ral 9011) (2020); Interpon D1036 Textura Powder Coating (ral 9017) (2020); Pow 85361-1 Cerchi Chiari (2019); Resicoat Powdercoat R4-es/hgf17r (2029)
  • Bso Metellverederlung: Qualicoat Paint Ral 7024 Matt (2013)

Resources and Citations

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