powder coatings:

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

+ + Fast DryingFast Drying++Deep shineDeep shine

EnamelsEnamels

- Long drying timesLong drying times- OxidationOxidation

+ + Good flexibility and Good flexibility and durabilitydurability+ + Cross-linkingCross-linking

UrethanesUrethanes

+ Dry fast+ Dry fast+ Very durable and + Very durable and

flexibleflexible

- Isocyanate - Isocyanate component is highly component is highly toxictoxic

HistoryHistory Late 1940’s- Flame spraying of thermoplastic powder developedLate 1940’s- Flame spraying of thermoplastic powder developed 1955- Dr. Erwin Gemmer patents fluidized bed application1955- Dr. Erwin Gemmer patents fluidized bed application 1962- Electrostatic spray method introduced1962- Electrostatic spray method introduced Late 1970’s- rapid growth in powder use in EuropeLate 1970’s- rapid growth in powder use in Europe Early 1980’s- rapid growth in North America and JapanEarly 1980’s- rapid growth in North America and Japan Today- Today-

• Fastest growing finishing technology in North AmericaFastest growing finishing technology in North America• Powder coatings account for >10% of all industrial finishing Powder coatings account for >10% of all industrial finishing

applicationsapplications• Powder coating engine blocks for automobiles is the largest volume job Powder coating engine blocks for automobiles is the largest volume job

in the history of the powder industryin 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 TypesPowder Coating Types

In general powder coatings offer excellent: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

OOH2C C

H

H2C

OHO O

H2C

O

H2C

O

Urethane Polyesters

+ Very good flexibility and weatherability

+ outstanding thin film appearance

RN

CO

R'O

NCO

* O

n

Polyurethane

N

N

N

O

OO

NC

O

NC

ON

CO

tris(6-isocyanatohexyl) isocyanurate

O CO

R'R CO

On

Polyester

Acrylics

+ Excellent color, gloss, weatherability

+ Excellent thin film appearance

- Fair flexibility and corrosion resistance

C C

CH3

C

**

OOCH3

H

H n

Poly(methyl methacrylate)

TGIC Polyesters

+ Excellent exterior durability

- Exposure limits when spraying due to TGIC

N

N

N

O

O

O

O

O

O

TGIC

O CO

R'R CO

On

Polyester

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 ApplicationsAutomotive Applications

Engine BlocksEngine Blocks FramesFrames Suspension and WheelsSuspension and Wheels Trim and MoldingsTrim and Moldings

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

Other Common ApplicationsMetal 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

ReferencesReferences• Industrial Paint and Powder Magazine Industrial Paint and Powder Magazine

http://www.ippmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/http://www.ippmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/0,6897,119461,00.html0,6897,119461,00.html

• North Carolina DENR Division of Pollution Prevention and Environmental Assistance North Carolina DENR Division of Pollution Prevention and Environmental Assistance http://www.p2pays.org/ref/01/00777/alternat.htm#General%20Description%203

• The powder coating institute- The powder coating institute- http://www.powdercoating.org/media/pressreleases/