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Epoxy Powder Coating. EMAC 276 April 15, 2009 Alexander Frayna, Leben Tefera , Amol Shetti , Lyle Zyra Case Western Reserve University, Cleveland OH . Background. Coating Covering aimed to improve surface properties or appearance Applied as a liquid, gas, or solid Powder Coating

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epoxy powder coating

Epoxy Powder Coating

EMAC 276

April 15, 2009

Alexander Frayna, LebenTefera, AmolShetti, Lyle Zyra

Case Western Reserve University, Cleveland OH

background
Background

Coating

Covering aimed to improve surface properties or appearance

Applied as a liquid, gas, or solid

Powder Coating

Durable finishing method for metals

Uses dry, powdered plastic

Heat-fused onto surface

Epoxies

Thermosetting Polymer

Excellent adhesion, chemical and heat resistance, mechanical

properties

epoxy powder coating1
Epoxy Powder Coating

Introduction in early 1960’s

Applications and Properties

Excellent protection in several environments

Prevention of corrosion

Heat Resistance

Increased Mechanical Strength

Electrical Insulation

Increased adhesion

polymer structure
Polymer Structure

Diphenol + epoxide

Structure of a Bisphenol A-epichlorohydrin type epoxy prepolymer

Key features

Number of monomers range from 0 to 25

Glycidyl ether end groups

http://tinyurl.com/cfqjja

reaction
Reaction

Reaction step 1

Reaction step 2

http://pslc.ws/macrogcss/eposyn.html

synthesis
Synthesis

BPA and ECH added to reactor in 1:1 ratio (slight excess of ECH)

Aqueous caustic soda

Reaction lasts one hour Taffy-like mass

Inert solvent added to cause phase separation

Solvent removed by vacuum distillation

http://pslc.ws/macrog/epoxy.htm

synthesis1
Synthesis

Cross-linking between prepolymers using secondary polyamine as curing agent

http://pslc.ws/macrogcss/eposyn.html

synthesis2
Synthesis

Large cross-linked network

Properties of resin determined by R group of amine

http://pslc.ws/macrogcss/eposyn.html

processing
Processing

Coated objects are typically conductive metals

Cleaning and surface preparation is essential

Typical pre-treatment process includes:

Clean

Rinse

Etch

Rinse

Conversion coating

Demineralized rinse

slide10
Powders contain resin, curing agent, and pigments

Two application techniques

Electrostatic gun application

Fluidized bed dipping

Powder is electrostatically charged before application

Electrical potential difference attracts powder to metal

Coatings are cured in ovens (160-210°C)

cost and competition
Cost and Competition

Typical powder coating installation (~$120,000)

Includes two wash booths, one dry filter booth, four automatic guns, one manual gun, and two reciprocators

Conventional solvent paint system (~$150,000)

Material costs

Powder- $27,000 per 1,000,000 sq.ft.

Solvent- $35,000 per 1,000,000 sq.ft.

Applied coating cost

Powder- $3.80/100 sq.ft.

Solvent- $5.66/100 sq.ft.

advantages
Advantages

∙ Excellent adherence to surface

∙ High corrosion/chemical resistance

∙ Convenient Storage

∙ Environmentally Friendly: No volatile diluter or solvent

∙ Near zero waste during application: Overspray may be gathered and recycled

advantages1
Advantages

∙ Running/Sagging/Flow Eliminated

∙ Low gloss, matte finish

∙ F – 5H Pencil Hardness

disadvantages
Disadvantages

∙ Difficult to produce smooth, thin layer

-Orange peel texture due to particle size

∙ UV degradation

- chalking

-less color retention/fade resistance

-White coatings tend to ‘yellow’

-Mostly for indoor use/out of sun

∙ High energy consumption in processing

recent technologies
RecentTechnologies

∙ Supercritical carbon dioxide used as solvent, eliminating the melt-mixing step and significantly reducing processing temperature. (Ferro, 1995)

∙ Electromagnetic brush coating (DSM Resins, 2004)

∙ Increased running speed

∙ Reduce Cost

∙ Decrease environmental impact

∙ Meet demand of high-tech market

thanks
Thanks!

References

1. Attar, M., Naderi , R., Moayed, M., (2005). Investig. on effect of various surface prep. on corrosion perform. of powder coated steel by EIS., Materials and Corrosion, 56, No.5, 325-328.

2. Li, G., Yuan, C., Chen, B. (2007). Explosion risk eval. during production of coating powder, J. of Haz. Mat., 149, 515-517.

3. Lothongkum, A., Nonthapone, R. (2006). Powd. charac. and coating conditions of fresh and reused polyester resins for electrostatic powd. coating: powd recycling and loss prev., Adv. Powd. Technol., 18, No.2, 175-186.

4. Misev, T., van derLinde, R. (1997). Powd. coatings technol.: new dev. at the turn of the century.. Progress in Organic Coatings. 34, 160-168.

5. Parra, D., Mercuri, L., Matos, J. (2001). Therm. behav. of the epox. and polyester powd. coat. using thermogravimetry/differential therm. anal.. Thermochimicaacta. 368, 143-151.

6. Shah, U., Zhang, C., Zhu, J. (2005). Compar. of electrostatic fine powd. coat. and coarse powd. coat. by numerical sim., J. of Electrostatics. 64, 345-354.

7. Stevens, M. Polymer Chemistry: An introduction. Oxford, New York. (1999). pp. 326-327.