High-pressure guns don’t have static mixing tubes. Rather, the chemicals are mixed together right at the tip of the gun. The product is so hot and under so much pressure, that it sets — meaning it goes from a liquid to a solid — very quickly, in about three to five seconds. Because the 1:1 ratio of chemicals in the high-pressure yield a product that’s very rigid, you’re limited on the texture — which resembles the surface of 80-grit sandpaper.
With low-pressure guns, the substance flows before it sets, leaving a flat glossy surface. Then, if your client desires, you can add a specific texture. Depending on which low-pressure gun you choose, liner texture can vary between raindrops and cottage cheese. However, the textures are more easily created with the guns that have the trigger switch, since you must periodically turn the system on and off to create the effect. Also, the guns without the trigger switch require you to check the chemical ratio each time you turn the gun on and off. The ratio is very important in all polyurethanes. If you’re not within a couple of percentage points of being right on the money, you’ll end up with goo.
Creating the texture:
If the customer asks for the cottage cheese or raindrop effect the best way to produce this is to apply the product, shut off the gun and a minute later applies a flash coat — which yields a flat and smooth non-textured surface. Then wait five minutes, change the atomization air, and literally throw the droplets on the truck bed, resulting in the desired texture.
Chemicals and Colors to Consider
Most polyurethane distribution companies you do business with will have you enter into a contractual arrangement. In other words, you promise to buy their proprietary chemicals and, in return, they give you a particular territory in which to conduct your bedliner business.
There are a couple of things you may want to think about when it comes to chemicals. For instance, even though their bases are similar, particular additives make them different.
First, look at isocyanate. With all polyurethanes, the isocyanate is one of the two main ingredients. There are many grades of isocyanate, and the higher grades are emanated from what’s called pure, modified di-isocyanate. If you were to compare this to grades of gasoline, the pure, modified di-isocyanate would be like the more expensive 93-octane fuel. The higher grades are clearer and more costly, while the lower grade isocyanates have a yellowish cast to them, making spraying colors more complicated.
The other component of polyurethanes is resin. The base of the resin is a polyol. However, multiple additives go into polyol, and each company has its own blend of additives, which offer different benefits and characteristics to the bedliner. In some cases, there can be as many as a dozen additives, and each combination can yield a different outcome. Make sure you know what you’re getting from your distribution company.
You also may want to consider a UV stabilizer as an additive. All polyurethanes have a tendency to be degraded by ultraviolet rays from the sun — or if people insist on parking their trucks in a tanning bed. The stabilizer acts like sunscreen. However, it can be expensive. For example, adding a quart of UV stabilizer sunscreen to a 55-gallon drum of chemicals adds 10 percent to the total cost of the drum. Is this too expensive? That’s for you to decide.