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Epoxy Powder Coatings

Epoxy Powder Coatings. April 18, 2012 - Group 9 Anise Grant Christopher Kumpf Tricia McCutchan Ricky Patel. Powder Coatings. Dry paint without a solvent No volatile organic compounds (VOCs). Polymers for Powder Coatings. Thermoplastics Vinyls PVC Thermosets Polyurethane

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Epoxy Powder Coatings

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  1. Epoxy Powder Coatings April 18, 2012 - Group 9 Anise Grant Christopher Kumpf Tricia McCutchan Ricky Patel

  2. Powder Coatings • Dry paint without a solvent • No volatile organic compounds (VOCs)

  3. Polymers for Powder Coatings Thermoplastics • Vinyls • PVC Thermosets • Polyurethane • Triglycidylisocyanurate • Epoxy/polyester hybrid • Epoxy

  4. Role of Epoxy in Coating Industry • Coating industry is largest consumer of epoxy resins

  5. General Applications • Interior/exterior coatings of pipelines in oil and gas industry • Electrical equipment insulation • Protection of reinforcing steel (rebar) • Decorative thin film coatings: indoor

  6. Componentsof Epoxy Powder Coatings • Simplest epoxy resin from reaction of Bisphenol A (BPA) and epichlorohydrin (ECH) • Commonly used curing agents: aliphatic amines, aromatic amines, ketamines • Common additives • Fillers: silica, clay, calcium carbonate • Pigments: chromic oxide, carbon black M. S. Bhatnagar (1996). Epoxy resins (overview). Polymeric Materials Encyclopedia [Online]. 1-11.

  7. Polymerization of Epoxy Resin Wicks, Z. W., Jones, F. N., Pappas, P. S., & Wicks, D. A. (2006). Epoxy and Phenolic Resins[Online]. 271-294. John Wiley & Sons, Inc. Retrieved from http://dx.doi.org/10.1002/9780470079072.ch13

  8. Physical Structure of Resin • Most epoxy powder coatings have a similar structure to epoxy made from BPA and ECH • Notable Physical Elements: • Aromatic rings that are prone to degrade with UV exposure • Epoxy groups (epoxides or oxiranes) are highly reactive sites where curing agents tend to bind Wicks, Z. W., Jones, F. N., Pappas, P. S., & Wicks, D. A. (2006). Epoxy and Phenolic Resins[Online]. 271-294. John Wiley & Sons, Inc. Retrieved from http://dx.doi.org/10.1002/9780470079072.ch13

  9. Processing of EpoxyCoatings Three step process: 1. Premixing - mixing an epoxy resin, curing agents, fillers in a hopper 2. Melt Extrusion - forms semi-liquid at high temperaturebut below curing temperature 3. Pulverization - Cooled then ground into a powder • H. J. Yu, L. Wang, Q. Shi, G. H. Jiang. Z. R. Zhao, and X. C. Dong (2006 Feb.). Study on nano-CaCo3 modified epoxy powder coatings. Progress in Organic Coatings [Online]. 55(3), 296-300. DOI: 10.1016/j.porgcoat.2006.01.007

  10. Cost • Varies with: • Supplier • Type of epoxy • Additives • Specific gravity (density) • Transfer efficiency • Film thickness • Examples: • Waste Powder Coating $0.62/lb • Chinapont $2.00/lb • FULL $1.19/lb

  11. Applying Coatingto Surfaces • Electrostatic spraying: most commonly used • Fluidizedbed coating Goal: fast curing with no shrinkage while maintaining good mechanical properties

  12. Electrostatic Spraying • Most common method of epoxy coatings • Powder particles are charged in coating gun • Surface to be coated is grounded --> attracts powder • Charged powder builds on surface until fully coated • Charged surface repels additional powder --> even coating layer • Powder coating is fused by curing with heat • High degree of powder re-usability • Easier to control thickness • Ron Joseph & Associates. (1991). A review of powder coating technologiesandapplication methods. Accessed on April 6, 2012. Available at:http://infohouse.p2ric.org/ref/23/22218.pdf

  13. FluidizedBed Coating • Procedure • Air blown through a container of epoxy powder • Powder acts like a liquid: promotes adhesion • Material heated to melting temp of the powder • Material dipped into powder container • Powder melts and adheres to material • No need for curing afterwards • Requires more skilled operator • Better with sharp edges and corners • Ron Joseph & Associates. (1991). A review of powder coating technologies andapplication methods.Accessed on April 6, 2012. Available at:http://infohouse.p2ric.org/ref/23/22218.pdf

  14. Overall Properties of Epoxy Powder • Excellent adhesiveproperties • Corrosion resistance • Chemical and solvent resistance • Electrical insulation properties • Mechanical strength, toughness, flexibility • Environmentally friendly from low volatile emissions

  15. Comparison to Other Powders • Epoxy falls behind powder coatings in: • Exterior durability • Heat and flame resistance • Excellent chemical resistancefor use in aggressive chemical environments • Hydrogen sulphide, carbon dioxide, methane • Poorresponse to prolonged UV exposure • Not to be used outside under intense sunlight

  16. Excellent Adhesive Properties • Can be applied to variety of substrates: • Metal • Wood (furniture) • Paper • Plastics • Adhesion to metal due to secondary hydroxyl groups along the polymer chains – hydrogen bond to metal oxide surface

  17. Corrosion Resistance • Aromatic groups in resin providegood barrier to: • Water • Oxygen • Ions known to cause corrosion • Prevents migration of ions through the coating and between the anodic and cathodic sites on the metal • Inhibits corrosion initiation • BUT: coating is somewhat permeable to some agents

  18. Requirements for Applications • Industrial coatings: thermal and mechanical properties determine the quality of the final product • Decorative coatings: chemical and abrasion resistance determine quality of the final product Main goal: develop coatings that cure at low temp and for shorter time while maintaining adhesion

  19. Applications of Epoxy Coatings • Corrosion-resistant thick filmsfor interior/exterior coatings of pipelines in oil and gas distributionindustry • Other piping: water and wastewater applications, valves, fittings, joints • Seawater resistance on ship hull • Insulation of electrical equipment • Automotive alternators, motors, switch gears • Protection of steel reinforcement http://www.portlandbridges.com/steel-bridge.html; http://www.123rf.com/photo_4396258_oil-and-gas-industry--pipelines.html; www.public.navy.mil/surfor/lcs1/Pages/OurShip.aspx; http://www.explainthatstuff.com/carengines.html

  20. Applications ofPowder Coatings • Toys • Shelving • Power tools • Furniture • Appliances • Hospital equipment • Floor coatings http://www.beyondthecarseat.com/?tag=toys&paged=2; http://power-tools.hardwarestore.com/65-384-cordless-drills.aspx; http://www.kitchenaiddishwasherpart.com/uncategorized/maytag-dryer-troubleshooting

  21. Current Problems • Volume shrinkage during curing process • Poor adhesion, warping, delamination, microcracks • Can become brittle after cross-linking • Weakened tensile and impact resistance • Nano-composites as possible solution • Poor UV resistance – can cause chalking • Aromatic phenol epoxies have weak weatherability • Poor thermal properties • Heat resistance • Flame resistance andretardance

  22. Future Development • Develop coating to achieve cathodic protection without the use of an additional system • Can only achieve separation of cathode and anode in a metal substrate if coating can wet surface completely on micro level • Coating must have low viscosity (depends on resin and application temperature) • Addition of organophosphates • To improve thermal properties

  23. Questions?

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