Acrylic/Melamine Clearcoats solve the problems of mar and scratch demage

When environmental fallout became an issue, clear topcoat technologies were developed to successfully solve the problem. Currently, mar and scratch damage as observed in the field is a problem receiving considerable attention. Car washes can be very abrasive. This wet abrasion action results in an undesirable visual dulling and a striped effect on nearly all current clearcoat technologies.

PPG uses nanoscratch testing instrumentation as a means to determine the energetics required to cause the various types of damage to clearcoats. In the commercially available nanoscratch testers, a film surface is moved in contact with a stylus under varying load conditions to create a scratch. The applied load at which the first film fracture (brittle failure) occurs, termed the critical load, is one measure of the film’s resistance to scratching. The technique also shows the amount of plastic deformation that results, as well as the amount of re-flow that occurs immediately after testing. UV-cured coatings are known for their excellent scratch and abrasion resistance.

The nanoscratch results show that a high level of scratch resistance is obtained when the forces required to cause brittle failure in the coating are high. The UV-cured clearcoat illustrates this point. Brittle failure, rather than ductile failure, is known to be the principal mechanism of visible damage. Load and depth at fracture in nanoscratch testing of clearcoats based on few existing technologies.

As stated above, the technology generally used in OEM clearcoats has been based on acrylic polyols that are crosslinked with melamine formaldehyde amino resin. A new clearcoat formulation that offers much improved scratch resistance has been reported by PPG Industries Inc.15 and is called CERAMICLEAR.