Powder Coatings:

1
Powder Coatings

• History, Types, and Applications

James Baker
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Outline

• Conventional Coatings
• Powder Coating History
• Types of Powder Coatings
• Advantages/ Disadvantages
• Applications

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Lacquers

• -Lack of durability
• -High maintenance
• -High VOC content

• Fast Drying
• Deep shine

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Enamels

• Good flexibility and durability
• Cross-linking

• Long drying times
• Oxidation

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Urethanes

• Dry fast
• Very durable and flexible

• - Isocyanate component is highly toxic

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History

• Late 1940s- Flame spraying of thermoplastic
  powder developed
• 1955- Dr. Erwin Gemmer patents fluidized bed
  application
• 1962- Electrostatic spray method introduced
• Late 1970s- rapid growth in powder use in Europe
• Early 1980s- rapid growth in North America and
  Japan
• Today-
• Fastest growing finishing technology in North
  America
• Powder coatings account for gt10 of all
  industrial finishing applications
• Powder coating engine blocks for automobiles
  is the largest volume job in the history of the
  powder industry

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Application Methods

• Electrostatic spray-
• Most common method
• High voltage, low amperage field generated by
  spray gun imparts electrostatic charge on powder
• Charged powder sticks to grounded substrate
• Object is heated in oven to cure, powder flows to
  form a continuous film

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Application Methods (cont)

• Fluidized Bed
• Heated object is dipped into an air fluidized bed
  of powder
• Electrostatic Fluidized Bed
• Similar to above, but powder particles are
  charged
• Flame Spray
• Powder is air fed through a propane flame
• Molten polymer is deposited on substrate
• Suitable for non-conductive substrates or very
  large objects
• Tribocharge
• Similar to electrostatic spray, but no
  high-voltage system
• Friction between powder and barrel induces weak
  static charge

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Powder Coating Types

• In general powder coatings offer excellent
• Hardness
• Corrosion protection
• Chemical resistance

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Epoxy

• Excellent flexibility
• Fair resistance to over-baking
• Poor exterior durability (low UV resistance)
• Epoxy-urethane hybrids
• Similar to epoxy
• Improved flow properties
• - Lower hardness

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Urethane Polyesters

• Very good flexibility and weatherability
• outstanding thin film appearance

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Acrylics

• Excellent color, gloss, weatherability
• Excellent thin film appearance
• Fair flexibility and corrosion resistance

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TGIC Polyesters

• Excellent exterior durability
• - Exposure limits when spraying due to TGIC

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Advantages of Powder Coating

• No VOC emissions
• Improved durability
• Over-spray may be reused
• Lower operating and maintenance costs for
  finishing lines

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Disadvantages

• Material must be able to withstand curing
  temperatures, gt260º F (125ºC)
• Forming films thinner than 1.5mil is difficult
• Electrostatic spraying may only be used for
  electrically conductive materials
• Powder is highly flammable
• Conversion from conventional to powder coating
  line requires large capital investment

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Automotive Applications

• Engine Blocks
• Frames
• Suspension and Wheels
• Trim and Moldings

• BMW and Volvo have developed powder clearcoats
• Chrysler, Ford, and GM have powder clearcoats in
  development

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Other Common Applications

• Metal Objects
• Appliances
• Highway signs
• Tools
• Lawn and garden equipment
• Office furniture
• A/V furniture and equipment
• Sports equipment

• Non-metal Objects
• Home-office furniture
• Kitchen cabinets
• Sinks/shower stalls
• Ceramics

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References

• Industrial Paint and Powder Magazine
  http//www.ippmagazine.com/CDA/ArticleInformation/
  features/BNP__Features__Item/0,6897,119461,00.html
  
• North Carolina DENR Division of Pollution
  Prevention and Environmental Assistance
  http//www.p2pays.org/ref/01/00777/alternat.htmGe
  neral20Description203
• The powder coating institute- http//www.powderco
  ating.org/media/pressreleases/