THE EFFECT OF COMPOSITION ON SURFACE PROPERTIES OF POLYESTER–MELAMINE THERMOSET COATINGS

Surface properties of polyester-melamine thermoset coatings have been investigated using XPS, thermal analysis methods, surface energy measurement, and small particle adhesion using a dedicated force rig. Bulk glass transition temperatures and surface energies changed little over a wide composition range (5–50?wt% melamine). At low melamine content (<20?wt%), particle adhesion behaviour was similar to that of pressure-sensitive adhesives; however, at high melamine contents particle adhesion was uniformly negligible. XPS and thermal analysis showed that at high melamine concentrations the surface melamine content was higher than expected, suggesting the formation of a hard, highly crosslinked, self-condensed, melamine-rich surface layer. This was not observed at lower melamine concentrations. The presence of this glassy melamine-rich surface layer is believed to be responsible for the low particle adhesion at high melamine concentrations.