Beyond Powder Coating


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Presentation by Kevin Lane for the Coating 2012 conference.

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  • I’d like to welcome you this morning to this presentation My name is Kevin Lane, and I’m the Director of Resodyn Engineered Polymeric Systems The discussion title is “Beyond Powder Coating” We are not suggesting this is a replacement for high-production component Powder Coating However, this is the solution for taking powder coating to surfaces previously denied the benefits of a powder coated finish. Our discussion will focus on the equipment technology and engineered materials which have taken powder coating out of the oven and into the field, where they can be applied and now even repaired with the same powder coating materials.
  • We’ll begin with a discussion of Polymer Thermal Spray or PTS for those that may not be familiar with the process And follow with a review of what is involved in creating a PTS coating since it differs greatly from the required processes of traditional powder coating. And we will also cover the development of equipment specifically designed for PTS, the requirements for materials if they are to perform in a PTS application, and the novel ability to perform repairs to Powder Coatings on location.
  • This is not an official published definition of thermal spray, its my own. Although I think it may be Wikipedia worthy, because it does a good job of capturing the essence of PTS coating creation. The process begins with a feed stock material – Obviously for Powder Coating the feed stock would be fine powders, but it could be polymers in the form of rod, wire, or pellets. The powder particle’s size varies when specified for PTS application. But in general, they are less than 400 microns for thermoplastic materials, and less than 100 microns for the thermosets. Unless it has been selectively sieved, the powder size, as we all know, is not a single uniform size throughout, but is always some distribution of coarse to fine particles centered around some mean. Managing this distribution curve can be useful in achieving the desired final coating properties. The powder particles are injected into a hot gas stream which heats and softens them as they are accelerated toward a pre-heated substrate surface. The softened particles strike the surface as splats which quite literally build up the coating thickness a splat at a time. Residual heat in the substrate and continued process heat cause the individual splats to coalesce into a complete cohesive layer. Finally, if the coating is a thermosetting material, the correct process temperature is achieved and the cross-linked cure is completed by the time the coating is cool.
  • This simulation illustrates formation of a coating layer as individual splats strike, flow, and coalesce to create a coated surface.
  • The main distinction to be made between polymer thermal spray and traditional powder coating is through the process by which each of them create a coating on a surface. Traditional powder coating is a multistep process that is accomplished in stages and over time. PTS coatings are created with the same basic process steps, all of which are occurring simultaneously during the normal application process. The bonding mechanism for PTS coatings is primarily a physical bond to the substrate. As with all physical bonding mechanisms, proper surface preparation will provide the foundation for a well-adhered long lasting coating. That being said, the surface preparation for PTS is fairly straight forward. The surface needs to be mechanically roughened which increases the surface area and changes the separation force angle, and it needs to be clean and degreased to remove any surface contaminates. The final consideration in PTS bond strength is pre-heating of the substrate surface. The surface temperature must be at or slightly above the melt temperature of the material being applied to ensure the first splats contacting the surface immediately melt into the roughened texture creating a strong bond. The rate a PTS coating can be applied in a given application is dependent on the polymer coating properties, and the amount of heat in the equation. A substrate with high thermal absorption, such as thick metals or concrete will require more thermal energy to process the powder into a coating.
  • The application of a PTS coating is similar to spray painting a surface. It should be accomplished with a smooth even spray deposition, with all the stages of coating formation from pre-heat to achieving full cure occurring during the normal application process. This requires a PTS system with sufficient thermal energy capacity.
  • This thermographic image video displays the temperature zones of a concrete surface as it is impacted by a column of hot air generated by a high-output, flameless PTS system. We can see with this graphic illustration the leading edge, lateral, and trailing edge process heat zones, as well as the oblong shaped, retained residual heat zone forming on the substrate. All of these are required and combine to allow for a continuous coating application process. The visual temperature scale shown on the right is in Kelvin.
  • Since the oven cure requirement has now been removed from the coating process, the real benefits of PTS coatings come from the ability to apply the a polymer coating to virtually any size component or structure, either in the shop or at the installation site. And now for the first time you can easily apply thermosetting materials in the field, and repair those coatings with equivalent materials.
  • Creating a sprayed polymer coating with a heat source is most certainly not a new concept. For more than three decades, many different thermal spray processes have been attempted and some have even gained limited use. However, several underlying issues are common among all the processes that adapt existing application methods to polymers that were originally designed for metals and other high temperature materials. The primary issues are that these processes are too hot and all but one has direct polymer interaction with flame, they are generally limited to thermoplastic materials unless they are coupled with a secondary cure mechanism, and several require extensive equipment systems rendering them unsuitable for field use.
  • Subjecting polymeric materials to direct exposure with the extreme temperatures of combustion or plasma generated thermal energy yields undeniably altered properties from that of the desired coating. These changes can be as minor as cosmetic discoloring or as severe as embrittlement. If there is one axiom in polymer coating chemistry, it is that polymers are degraded through direct exposure to the high temperatures of an open flame. Propane and air combusts at 2000°C. Air forced through a plasma plume exits at a temperature greater than 4000°C. Polymers suitable for use in most coating formulations degrade at temperatures far below these direct flame interaction processes in the general range of 200°to 350°C. You will notice the distinctly yellow flame spray plume shown on the right. We all know that combusting propane and air produces a clear or slightly blue flame. The yellow color clearly indicates burning polymer is being applied to the substrate. This is clearly shown in the flame spray photomicrograph displaying a high percentage of burned particle inclusions.
  • Early in the PTS technology development process, analysis was conducted to fully understand and illustrate the phenomenon of polymer particle heat and flow transport principles.
  • As the objective was an application technology that would quickly heat polymer particles to the desired temperature without any degradation, it was also imperative to gain an understanding of polymer particle heat absorption and subsequent temperature rise when traveling in a hot gas path.
  • It was determined early in the development process that the real solution was a combination of equipment and materials designed and engineered specifically to be used together. The original design specification called for a flameless heat source with tightly controlled output that would not just deposit the polymer powders, but would process the materials into complete coating finishes.
  • The first approach to developing an application system specific to polymers was to utilize an all electric heat source. Introducing the polymers down stream from a truly flameless heat source maintained absolute polymer integrity.
  • As our project experience progressed, we recognized that achieving industry acceptable application rates would require a system with much greater thermal output capacity. Without deviating from the original technology design criteria, a propane and air combustion powered system was designed that accomplishes two critical requirements; those being no powder and flame interaction ,and control of the output temperature, both of which then eliminate the possibility of polymer degradation. The result was an applicator that locks the combustion flame down onto the burner face plate so that only a column of hot air is generated and propelled from the front of the applicator. And, through a unique combination of amplified air systems, the propane combustion temperature of 2000°C is tempered to material appropriate temperatures ranging up to 700°C. The polymer powder is injected axially through an air cooled, shielded feed tube into the core of the hot air column safely beyond any extreme temperature zones.
  • The development of this new technology made it possible to greatly expand the list of materials initially thought to be candidates for thermal spray. Until very recently, only thermoplastic materials, and thermoset materials with alternate curing methods such as U.V. were utilized for the process. The flameless application process changed that and now allows for thermoset materials utilizing chemical cure mechanisms to be engineered to complete their curing process during the normal PTS application process.
  • In addition to cure temperatures and shortened durations, PTS materials are engineered to optimize the application process to improve deposition and coverage rates. Additionally, the application equipment design makes it possible to create coatings with fillers, additives, and coating blends that simply would not be possible with conventional coating methods.
  • One of the greatest changes this technology brings to the powder coating industry is the ability to now perform touch-up and repairs to powder coated surfaces with equivalent materials, and to accomplish these repairs in the field without having to strip the component or even remove from service.
  • Our materials team is continuously developing general use and client or application specific coating materials for use with the PTS systems. The current list of active projects include a broad spectrum of applications for commercial clients in the entertainment industry, paper production, and waste water, and agency projects in highway safety, military asset protection and protection of domestic infrastructure.
  • This short video demonstrates the PTS application of a thermoplastic coating for metals, followed by a thermoset coating being applied and cured in place also on sheet metal. As we watch the material being deposited, think back to the thermographic imaging analysis video we viewed earlier illustrating the effective heat zones created by the PTS thermal output. Especially with the dark blue color, you can easily see the material transition through the stages of splat strike, flow, and coalescence into a smooth coating layer. This is only possible in a continuous process application because of the effective heat zones working the surface concurrently during the spray application. The surface ahead of the spray is being preheated to ensure first splat adhesion. The zone directly under the applicator is softening and partially melting the particles in flight. The lateral and trailing heat zones are adding heat to the equation to flow and coalesce the already deposited material, and are assisted by the residual heat working from the back side of the applied coating to complete the finish. These last zones are ultimately important for thermosetting formulations, as they are what ensures coating cross-link is initiated and provides the time-at-temperature duration necessary to complete the cure.
  • So, now that powder coating is out of the oven, we now have the ability to apply fully-cured coatings in the virtually anywhere and onto any surface. And, since this is the first commercial field repair powder coating process, the total system is in reality a game changing technology that is going to forever change the way people think about powder coating.
  • Thank you very much for attending this presentation.
  • Beyond Powder Coating

    1. 1. + Beyond Powder Coating! Field Applied, Fully-Cured Powder Coating Technology
    2. 2. + Overview  What is Polymer Thermal Spray (PTS)?  PTS Fundamentals  Benefits of a PTS Coating  Background  Flameless Technology Development  PTS Specific Materials  Field Repairable Coatings  Current PTS Coating R&D Contracts  Flameless PTS Application Video  Summary October 9-11, 2012
    3. 3. + What is Polymer Thermal Spray? The deposition of semi-molten polymer particles onto a pre- heated surface whereby process heat causes the particles to flow and coalesce into a complete cohesive polymer coating. Splats – unit building blocks of thermally sprayed coatings  Polymer rheology Define Coating  Degree of melting Formation Process  Impact velocity October 9-11, 2012
    4. 4. + PTS Fundamentals Splat Formation Simulation Watch this video on YouTube October 9-11, 2012
    5. 5. + PTS Fundamentals  Traditional Powder Coating process enjoys the luxury of time - PTS must accomplish all coating steps in a single application process at industry acceptable coating deposition rates  Primarily physical bonding to substrate  Surface preparation – clean, roughen surface, degrease  Pre-heat substrate for first-strike splat adhesion  PTS coating deposition rate dependent on  Coating properties – chemical and physical  Substrate thermal absorption properties  Process thermal energy capacity October 9-11, 2012
    6. 6. + PTS Fundamentals  Sufficient process thermal energy required for continuous application process  Pre-heating ahead of deposition  In-flight softening of particles to semi-molten state  Immediate flow-out of first-strike splats to provide adhesion  Accelerated temperature rise of material to begin coalescence  Post-heating to flow material into uniform cohesive layer  Post-heating to achieve complete cross-link cure  All simultaneously occurring during normal spray application October 9-11, 2012
    7. 7. + PTS Process Thermal Energy Process Heat Thermographic Analysis Watch this video on YouTube October 9-11, 2012
    8. 8. + Benefits of PTS Applied Coatings  No oven cure required  No longer limited to oven size  Flexible – Field portable or fixed manufacturing operation  No Volatile Organic Compounds (VOC) or Hazardous Air Pollutants (HAP)  Field repairable  No overspray containment issues  Standard surface preparation – No pre-treatments or primers  Coated surface is immediately ready for service when cool  Broad range of Thermoplastic and Thermoset materials  Easy clean-up and color/material change October 9-11, 2012
    9. 9. + Background – Historical Methods  Historical adaptation of legacy processes  Flame Spray  Plasma Arc Spray  HVOF  Cold Spray  Issues  Designed for high-temperature, dense materials  Not generally practical for field use  Limited to a few select polymers  Limited acceptance and use October 9-11, 2012
    10. 10. + Background – Polymers vs. Flame Flameless PTS Flame Spray Technology Flameless Flame Spray PTS Coating Coating Polymers Polymers Mild Hot Flame Gas October 9-11, 2012
    11. 11. + Flameless Technology Development  Polymer particle heat and flow transport principles Temperature Degrees Celsius PTS Nozzle Particle Acceleration Particle Heating (Cp = f(T)) Drag Vp Vg A Conduction Convection October 9-11, 2012
    12. 12. + Flameless Technology Development  Particle heating during acceleration in hot air stream Polymer Particle Diameter: 300 μm PTS Gas Temperature Nozzle Typical Spray Distance (5 kW System) Particle Surface Particle Core October 9-11, 2012
    13. 13. + Flameless Technology Development  PTS required a total solution  Completely novel application technology designed specifically for polymers  No polymer degradation  Apply a full range of materials  Operational flexibility  Polymer powder coating formulations specifically designed with properties to perform with PTS application  Adhesion  Flow and coalescence  Application temperature / In-service temperature  Robust chemistry – resistant to defect causing contaminants  Cure rates – time and temperature October 9-11, 2012
    14. 14. + Flameless Technology Development  Electric heat source selected for initial development  Closed-loop temperature control  Polymer particles injected down-stream from heat source  Later designs increased system thermal output from 5 kW to 15 kW to increase deposition rates for coating large surfaces  2 kW system developed for small area touch-up coating repairs Electric Heat Source System Electric 5 kW PTS Applicator Three systems with output up to: 2 kW 5 kW 15 kW October 9-11, 2012
    15. 15. + Flameless Technology Development  Transitioned from electric to combustion heat source to improve coating deposition rates  Flameless design criteria maintained throughout substantial increases in thermal output capacity  Flame locked down onto burner plate  No polymer / flame interaction  Only a column of hot process air exits the front of the applicator “Flameless” PTS System Only hot air contacts polymers  Polymer powder is injected through shielded feed tube Propane/Air Combustion High Output System 7– 30 kW Watch this video on YouTube » October 9-11, 2012
    16. 16. + PTS Specific Materials Development  Thermoplastic  Wide range of base resin selections PE PP PA  Thermosetting EMAA PMMA  Polyesters, Urethanes, Epoxies EAA FLAMELESS EVA PTS  TGIC free formulation  Hybrid Formulations POLYESTERS  Thermoplastic / Thermoset POLYURETHANES EPOXIES October 9-11, 2012
    17. 17. + PTS Specific Materials Development  Engineered coating formulations  Specific to PTS process requirements  Coating properties enhanced for peak performance  Unique coating creations possible  Multi-component, in-flight materials blending (dry-blending)  Coating formulations with large disparity in component size  Spray method induced coating surface features October 9-11, 2012
    18. 18. + Field Repairable Powder Coatings  Repair and touch-up damaged powder coated surfaces with same powder coating material Damaged  Repair both thermoset and thermoplastic Coating coatings  Strip and recoat not required  Prepare damaged area similar to paint touch-up  Repair in-service components Repaired Coating  Powder coat fasteners, brackets, welds, etc. after installation October 9-11, 2012
    19. 19. + Current Coating Projects  Amusement Park and Resort facility: Corrosion, wear and artistic creation coatings  Pulp and Paper: Corrosion and specialized wear coatings  Waste Water Facility: Containment and concrete corrosion protection  U.S. DOT: Concrete highway barrier coating to mitigate tire climb induced vehicle rollover after impact  U.S. Air Force: Friction reducing wear coating for C-130 aircraft skids for Arctic region operation  U.S. Navy: Life extension of above waterline radar installations through PTS field applied coating repairs  U.S. Dept. of Homeland Security: Energy absorbing foam for blast protection of infrastructure  U.S. Army Research Laboratory: CARC compliant powder coating qualified to MIL-PRF-32348 October 9-11, 2012
    20. 20. + Flameless PTS Coating Application Watch this video on YouTube October 9-11, 2012
    21. 21. + Summary  PTS total solution - materials and equipment  Continuous application process  Powder coating is now out of the oven  First commercial field repair powder coating process Beyond Powder Coating! October 9-11, 2012
    22. 22. + Thank you for your attention For further information please visit Resodyn at: Contact information: Kevin M. Lane Director, Resodyn Engineered Polymeric Systems 406-497-5288 October 9-11, 2012