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
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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. +
PTS Fundamentals
Splat Formation Simulation
Watch this video on YouTube
October 9-11, 2012
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. +
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. +
PTS Process Thermal Energy
Process Heat Thermographic Analysis
Watch this video on YouTube
October 9-11, 2012
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. +
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. +
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
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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
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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
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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
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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. +
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. +
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. +
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
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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
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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. +
Flameless PTS Coating Application
Watch this video on YouTube
October 9-11, 2012
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. +
Thank you for your attention
For further information please visit Resodyn at:
www.resodyncoatings.com
Contact information:
Kevin M. Lane
Director, Resodyn Engineered Polymeric Systems
406-497-5288
kevin.lane@resodyncoatings.com
October 9-11, 2012
Hinweis der Redaktion
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.