Powder Coatings: History, Types, and Applications James Baker

Outline  Conventional Coatings  Powder Coating History  Types of Powder Coatings  Advantages/ Disadvantages  Applications

Lacquers -Lack of durability -High maintenance -High VOC content + Fast Drying + Deep shine

Enamels -Long drying times -Oxidation + Good flexibility and durability + Cross-linking

Urethanes + Dry fast + Very durable and flexible - Isocyanate component is highly toxic

History  Late 1940’s- Flame spraying of thermoplastic powder developed  Dr. Erwin Gemmer patents fluidized bed application  Electrostatic spray method introduced  Late 1970’s- rapid growth in powder use in Europe  Early 1980’s- rapid growth in North America and Japan  Today- Fastest growing finishing technology in North America Fastest growing finishing technology in North America Powder coatings account for >10% of all industrial finishing applicationsPowder coatings account for >10% of all industrial finishing applications Powder coating engine blocks for automobiles is the largest volume job in the history of the powder industry Powder coating engine blocks for automobiles is the largest volume job in the history of the powder industry

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

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

Powder Coating Types  In general powder coatings offer excellent: HardnessHardness Corrosion protectionCorrosion protection Chemical resistanceChemical resistance

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

Urethane Polyesters + Very good flexibility and weatherability + outstanding thin film appearance

Acrylics + Excellent color, gloss, weatherability + Excellent thin film appearance -Fair flexibility and corrosion resistance

TGIC Polyesters + Excellent exterior durability - Exposure limits when spraying due to TGIC

Advantages of Powder Coating  No VOC emissions  Improved durability  Over-spray may be reused  Lower operating and maintenance costs for finishing lines

Disadvantages  Material must be able to withstand curing temperatures, >260º 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

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

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

References Industrial Paint and Powder Magazine 0,6897,119461,00.htmlIndustrial Paint and Powder Magazine 0,6897,119461,00.html North Carolina DENR Division of Pollution Prevention and Environmental Assistance Carolina DENR Division of Pollution Prevention and Environmental Assistance The powder coating institute- powder coating institute-