Issue link: https://ppgrefinish-na.uberflip.com/i/1031702
The Chemistry Refinish clearcoats are made up of urethane resin technology that's cross-linked with an isocyanate hardener. Several chemistries comprise a clearcoat: RESIN The resin is the foundation of any clearcoat and plays a significant role in how it sprays, how fast it cures, its hardness, its VOC content and its overall durability. Since the resin is designed to be cross-linked with an isocyanate hardener, correct mix ratio is critical to achieving the proper reaction. If not mixed properly it can create a host of problems. And of course, when spraying any paint product containing isocyanate, it's essential that the proper respirator and safety equipment be worn. ADDITIVES This type of chemistry adds to the performance of the clearcoat in several ways. It can improve the atomization of the liquid to make it easier to apply and achieve better overall appearance with less orange peel. Additives can also affect how the clearcoat lays down–its flow and leveling characteristics. CATALYSTS Added in very small amounts, catalysts can speed up the reaction between the resin and the isocyanate hardener. The faster reaction however can shorten the clearcoat's pot life and limits the window of time allowed to spray it. If the reaction is too fast, it may cause "solvent pop" or dieback by not allowing solvents to escape from the film before the curing takes effect. SOLVENTS When added to the clearcoat, solvents help dissolve the resin, additives and catalysts to control the application and flow. A blend of solvents with varying evaporation rates is used. "Fast solvents" reduce the clearcoat's viscosity and evaporate during atomization out of the spray gun. "Slow" or "tail" solvents stay in the film longer during the wetting of the substrate and allow the clearcoat to flow and level out properly. The Clearcoat's Important Role The adoption of basecoat-clearcoat finishes by OEMs in the early '80s represented a marked advance over single-stage color systems. By providing a coating over the base color, the clearcoat not only provides superior gloss, it protects the color from fading due to the sun's damaging ultraviolet rays—as well as enhances appearance, scratch resistance and overall durability.