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
April 15, 2009
Alexander Frayna, LebenTefera, AmolShetti, Lyle Zyra
Case Western Reserve University, Cleveland OH
Covering aimed to improve surface properties or appearance
Applied as a liquid, gas, or solid
Durable finishing method for metals
Uses dry, powdered plastic
Heat-fused onto surface
Excellent adhesion, chemical and heat resistance, mechanical
Introduction in early 1960’s
Applications and Properties
Excellent protection in several environments
Prevention of corrosion
Increased Mechanical Strength
Diphenol + epoxide
Structure of a Bisphenol A-epichlorohydrin type epoxy prepolymer
Number of monomers range from 0 to 25
Glycidyl ether end groups
Reaction step 1
Reaction step 2
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
Cross-linking between prepolymers using secondary polyamine as curing agent
Large cross-linked network
Properties of resin determined by R group of amine
Coated objects are typically conductive metals
Cleaning and surface preparation is essential
Typical pre-treatment process includes:
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)
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)
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.
∙ 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
∙ Running/Sagging/Flow Eliminated
∙ Low gloss, matte finish
∙ F – 5H Pencil Hardness
∙ Difficult to produce smooth, thin layer
-Orange peel texture due to particle size
∙ UV degradation
-less color retention/fade resistance
-White coatings tend to ‘yellow’
-Mostly for indoor use/out of sun
∙ High energy consumption in processing
∙ 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
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