Question
We make a few exterior items. I'm looking for anyone who has used ML Campbell Euro X. I have the info from Campbell, but how does it really work? I've heard that the fumes made the fellow spraying it sick, physically. We currently use Sikkens and are pleased, but if there is something easier, cheaper, and better, I'd like to know.
Forum Responses
(Finishing Forum)
From contributor B:
I have been using this product for about 7 months on some projects that need polyurethane. The Euro-x is a very user-friendly product. I've used it on everything from Spanish cedar garage doors to a MDF kitchen.
The product likes to be retarded at 10%, no matter what the humidity level is. One needs to be extra careful when mixing the different coatings, as the catalyst for all the coatings is a different blend. They do make it user friendly by applying a color code that's visible on the cans, and the mixing ratios are also on the can. One doesn't need a spec sheet in order to mix any of the sealers or topcoats. The mixing ratios are all different, and I suppose that's the reason for labeling the can. Sealer is purple, clear satin is yellow, high gloss clear is blue, and pigmented satin is green. They all go over a clear sealer and can be tinted to any color with 844's.
The only problem is spraying the product with small component pumps. The down stroke is not equivalent to the up stroke, which results in air trapment due to the shearing action. I tried it on a 10 to 1 Kremlin and had a problem in the topcoat, even retarded at 10%. I used a Devilbiss kb2 pressure pot with #764 tip and the results were good. As is the case with all polyurethanes, they don't like to be pressurized. I will be doing some testing with a larger component pump on the next job, and I think that the more even up stroke and down stroke will eliminate the problems with the air trapment in the topcoat.
"I questioned if you were applying too great of a film thickness, however 2 mils is not excessive. In most spray systems, there is a correlation between nozzle size, fluid pressure and the resulting flow rate. The viscosity of the material you are spraying may be high, so in order to get the required flow rate through a given nozzle size, you must increase the fluid pressure. Conversely, you can get the same flow rate using a larger nozzle size and a lower fluid pressure. Micro-bubble can be caused by sheer forces when a fluid exits an orifice at too high of a velocity. So a larger nozzle and lower pressure should reduce the bubble."
I know this can also be a problem when spraying solid colors. Somehow the pressure kicks the tinter out. So far as bubbles caused by shaking - I always thought that was one of those sprayer's myths. Does anybody have any real info on whether bubbles can survive being atomized?
P.S. The defoamer is to prevent foam. I don't know that foam carries through the gun.
The reason chemical manufacturers use anti-foaming agents is shipping and transit of materials. Most coatings are delivered via common carrier trucks. The product gets shaken up in transit and foam accumulates within the space at the top of the can. If it weren't for the anti-foaming agents, the foam would remain constant instead of settling back into its original state. I don't think anyone has to worry about foam going through their guns.
1. Shaken and not stirred. Most spray equipment atomizes finishes by injecting vast quantities of air into them, so what do some bubbles in the can matter? Brushed on varnish is usually recommended to be stirred and not shaken because its high viscosity would not let the bubbles rise to the surface and pop. I may be wrong, but anti-foaming agents are generally used only in waterbourne finishes. There is a difference between foam and bubbles.
2. Micro bubbles. If the pick-up tube of the pump is submerged in liquid, where does the air come from to make the micro bubble? If you picked up air from the tube, you would lose the prime on the pump.
Most AAA guns optimally atomize material by producing 400 to 600 psi of fluid pressure at the tip. The sheering action takes place as the liquid exits the nozzle of the gun at too high of a fluid pressure. In effect, it is over-atomized. The droplets of finish it is producing are too small. As those tiny droplets land on the wood's surface, they have tiny air spaces around them. As the droplets flow together, some of the air in these tiny spaces gets trapped, producing teeny tiny bubbles. These tiny bubbles are not very buoyant compared to the viscous liquid they are suspended in, so they can not float to the surface fast enough to break, and thus they get trapped in the layer of dried film. A larger droplet will have larger spaces around it, and thus produce bigger bubbles, which are able to float to the surface faster, break and re-heal.
A 10:1 pump mechanically works the exact same way as a 30:1 pump. The two differences are that the 30:1 produces 3 times the amount of fluid pressure at the tip for every pound of input air compared to the 10:1 pump. Also, the 30:1 can produce a higher sustained fluid delivery rate, in ounces per minute, as the 10:1. Why is this important? It's all about the flow. You want a certain flow rate in order to lay down a nice wet coat in a reasonable amount of time. As the viscosity goes up, so does the required flow rate. 2k poly has a higher percentage solids by volume ratio than, say, a pre-cat, so it will also have a higher viscosity.
You can increase the flow rate two ways... Increase the fluid pressure or increase the nozzle size. If you increase the fluid pressure too much, you run the risk of micro-bubble (as per above), so the alternative is to use a larger nozzle with a lower fluid pressure behind it. You could use a 10:1 pump, but a 10:1 pump with a lower fluid delivery rate (ounces per minute) will be working like a dog to keep up with the demand of the nozzle, whereas the 30:1 will barely be breaking a sweat. Finally, you could reduce the viscosity of the material and go back to a smaller nozzle.
When you went to the larger size pump, did you check out the size (flow rate) of the nozzle in it compared to the 10:1 pump?
You indicated that you couldn't understand how air bubbles could form out of a nozzle. The pick up tube running out of fluid is one of the options, but is not what's taking place here. The shearing action or pockets of air are created at the top of the stroke or the bottom of the stroke, when the movement is uneven at this point . The larger pumps are designed to have equal motion on both strokes and that's the reason they work. As I indicated earlier, my viscosity is not the problem and it really has nothing to do with my air pressure and fluid tip sizes. If I use more air pressure, more pump pressure, and a larger tip, then I can see my transfer efficiency going right out the window. The object is to paint the product, not the ceiling, walls, and floor around the product. I use the same tip for all my finishes on both pumps, 10 to 1 as well as 30 to 1. How does one reach the recommended viscosity on all finishes without using thinner? Do you use catalyzed products? What do you do with your leftover catalyzed product at the end of the day? Do you throw it out ? Do you seal all exposed wood on what you spray, seen or unseen?
Viscosity is a function of percent solids by volume and temperature. So if you need to lower your viscosity, you either add a reducer or raise the material temperature. Most manufacturers state the viscosity of their material in the can at a certain temperature - Campbell uses 77 degrees. The viscosity required is by a particular piece of equipment, with a specific nozzle/needle/air cap, usually different than what is stated on the can. You need to adjust the viscosity to fit the piece of equipment you are spraying it with. Most people do this with solvents, since heat systems can be complex and will shorten the pot life of catalyzed products.
I shot 2k polys almost exclusively for over 12 years. Many brands through most types of equipment. I let the leftovers harden and then had it hauled away with our liquid waste. Our standard procedure was to seal all surfaces.
Many customers' needs are better served with a lower-rated coating that can be maintained. Maintain the coating before it degrades, and you are good to go until the next maintenance call. It's good all around - happy customers who pay for maintenance contracts, and finished items which can be revived without having to strip off the five year old "sherman tank" coating.
As for interior use, I bet the MLC 2k PU is swell. But did I hear a quote of up to $80 a gallon including the sealer? Ilva weighs in at about $26 a gallon. Um...
Comment from contributor P:
I think the problem is related to the isocyinate hardener and high humidity. As water laden air travels over a wet film during film formation, water reacts to the isocyinates in the hardener causing a CO2 explosion which results in tiny blisters or bubbles in the film. I studied in Germany with a German automotive paint company and all of your modern automotive topcoats are basically the same technology.
