The complexity of the task may be one reason why the number of gel coat manufacturers has shrunk from 20 at one time to four or five today.
“You look at the technology, at the economies of scale, you look at what it takes to be consistent and you can see it has gone from mom-and-pop operations to a more industrial design product in a plant,” says Crump. “When I first started, the company I was working for had literally started in a garage. They would not be able to do that today for a variety of reasons.”
Gel coat manufacturers have to design their products for both the immediate customer – the fabricator – as well as the end user. For fabricators, a gel coat has to produce consistent results. “It’s like paint, but it has to be able to be sprayed and it can’t run or drip,” Pauer says. That’s challenging with a material that is usually applied at 15 to 35 mils in thickness… . In addition, gel coats must perform well over a range of temperatures, since some fabricators may not have good environmental controls in their shop.”
Porosity is also an issue, Pauer adds. “We generally spray or brush on this material, but you can’t have any type of air voids because you could affect its continuous film characteristics. If there’s a hole in that film, if there’s porosity or a fish eye, that allows water to ingress and it looks like a defect on the surface. It also affects corrosion resistance, water resistance, the UV resistance – all of those things that you are using the gel coat for come into play.”
Gel coat formulations also vary by application method. Crump says the vast majority of composite fabricators in the U.S. today spray gel coats into an open mold as the first layer of a composite part. “The gel coat forms a strong chemical bond to the resin,” he says. “The individual layers become monolithic, because they are essentially bonded together. That’s one of the reasons that we use gel coats instead of just painting the outside of the surface with some other type of coating. It’s really durable because it’s not a physical bond to the surface, it’s a chemical bond.”
Composite product manufacturers apply the remainder of gel coats to existing structures as a post-finish layer. These surface coats add a thick, durable layer to a product’s surface.