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Switching from thermoset to thermoplastic? Top 5 things to consider...
Thinking about switching to or adding thermoplastic powder to your coating operation? Make it as smooth as possible and check out our top 5 things to consider:
5. Dip vs. Spray
Thermoplastic powders work well in both fluid bed coating (FBC) and electrostatic spray operations, so there is a choice to be made. This topic could be an article in itself (and maybe it will in the future!) but let’s touch on some of the main points.
First off, what are you coating? The entire part must be dipped into the fluidized powder all at once, so the size of the part drives the size of the fluid bed, and how much powder is required to charge the bed before a single part can be coated, for each color.
In fact, the shape of the part is generally the most important aspect of this decision. The powder is a fluid in this process and has to replace any air pockets to actually coat the part. There are some parts with interior surfaces that are almost impossible to fluid bed coat with good results. The converse to this is a part like a wire good is much better suited to fluid bed coating.
Without going into too much detail, if the part shape works, you intend to use the line for dedicated parts, you can withstand the limited flexibility of the line, and have limited color changes, fluid bed coating may be the right decision. If you need an all purpose line that that is flexible, coating a variety of shaped pieces with a variety of colors at any given time. electrostatic spray is probably the way to go.
4. Get your space back!
Space is a premium – we all know that! Thermoset powder coatings, with their heat-initiated thermo setting reaction, generally need to be stored in climate control environment. As you transition from thermoset to thermoplastic, the need for climate controlled storage may be greatly reduced, or in a 100% conversion, completely eliminated. With thermoplastic powder, you now have the freedom to disperse your powder coating inventory wherever you’d like to store it. The possibilities of what to do with the newly freed up space can be exhilarating: an additional coating booth, improve material flow through the plant or repurpose the space completely!
3. Lay it on Thick: Preheating options for high film builds
Many thermoplastic applications benefit from using higher film thicknesses and sometimes, the film thickness and the coating performance increase together. For example, 25 mils of Puroplaz PE15 on a freshly clean part will give you gravelometer results that are OFF THE CHART!
However, there are some challenges achieving high coating thicknesses in an electrostatic application on a continuous line. Preheating the part prior to coating is one of the best tricks of the trade to overcome these issues. Once the particle melts on the hot surface, it gives up its electrostatic charge allowing more charged coating to be applied. There are many options to achieve the part temperature. (gas ovens, electric ovens, Infra-Red, etc.) and if preheating is going to be part of your process, it best to put in the research and find out which heating method is best for your application. The earlier in the transition you address this, the easier the installation of the new heating capability.
2. Racking the Brain – Easy does it
We have two transition racking points to make.
First, unracking the part. Thermoplastic powders need to cool down below the softening point before handling. So if you have a thick part that cools slowly, your will need to either plan for the longer cool down time, or add cooling to your process with fans, water quench/misting, etc.
Second, the thicker film thickness associated thermoplastics generally results in having to burn off the racking more often to achieve good grounding. You will need to plan for this!
1. Setup for Success – Spray Equipment
Let’s keep this simple…..If you are using a quality thermoplastic powder and have properly functioning electrostatic equipment with the proper settings, the resulting powder cloud, attraction to the part, and wrap, etc. are exactly like conventional thermosetting powder coatings. If not, something is off. So, how to address this? Making sure it says Puroplaz on the box is always a good start J. Your Puroplaz Technical Service Rep is a great resource in making sure your equipment is setup correctly, and bring in your equipment supplier if needed. From there, the proper settings can be dialed in: look at KV and amperage settings, airflow, fluidization levels, etc. Since this is a transition from thermoset to thermoplastic, investing in your electrostatic equipment (service, replacement parts, etc.) will be money well spent. Almost any equipment set up will work for thermoplastic powder. But if you are buying or upgrading your equipment for this transition, talk to your Puroplaz Technical Service Representative, who will help you with information for your personal application, space and line requirements.