February 20, 2014
Not Necessarily the Best of Both Worlds
Let’s take a common powder coating hybrid: an epoxy-polyester blend. It could seem like an epoxy-polyester hybrid powder coating would allow you to combine the weather resistance and smoothness of polyester with the chemical resistance of epoxy. Not so. As our COO, Dave Arney, notes, “You always have to go to the weakest link when it comes to properties of hybrid coatings.” So, for example, when evaluating the chemical resistance of an epoxy-polyester blend, you measure not how resistant the epoxy is but rather how much the resistance of epoxy is degraded by the less chemically resistant polyester. Inversely, in order to evaluate the weather resistance of this blend, look not to the normal weather resistance of polyester but to how much that resistance is degraded by the addition of epoxy.
But Still, There Are Advantages
Cost. Taking the above example, an epoxy-polyester hybrid, you’ll find that the hybrid coatings are much more competitively priced than the pure epoxy coatings. This holds true for a number of hybrid coatings.
Performance. Although we described the performance tradeoffs above, there are reasons besides cost that companies use hybrid coatings. Sometimes the performance compromises are worth the additional qualities that you’ll get out of a hybrid coating (like a smoother epoxy) – it all depends on the environment and use of the part.
Xylan coatings are perhaps the best-known and most trusted coatings for industrial use. Most Xylans blend a polyamide and PTFE to create high-end hybrids that deliver excellent performance with very little compromise. For example, Xylan 1331 is a dry-film lubricant that contains both PTFE and PPS (also known as Ryton). The PTFE delivers the low coefficient of friction and the chemical resistance, while the PPS adds hardness and creates a non-porous surface. The result is an excellent lubricant with increased abrasion resistance.
While many companies, such as Whitford, create hybrids that don’t demand too much compromise, there are other options for getting the combination of qualities that you need. Dave Arney notes that one alternative approach is to layer coatings rather than blend them. Why layer? In the first place, the coatings that you want to blend may not be chemically compatible in a blend. PTFE, which is chemically inert, is easier to blend, but more chemically reactive coatings might not fare so well. Secondly, sometimes layering allows you to get the properties of the coatings you want with little to no degradation of the properties of each coating. But just as custom hybrids require an experienced coater to make sure that the application and curing go right based on the properties of both coatings, it also takes an expert applicator to layer coatings correctly for a durable, high-quality finish.