The concern regarding the effect of chemicals on the environment has increased considerably in recent years.
Nowadays, technological developments in the coating industry are largely influenced by environmental issues
and subsequent legislation. One of these issues is the tendency to replace cobalt as a catalyst with more
environmentally friendly alternatives, because studies have indicated possible carcinogenicity. Not much
knowledge is available on the effects of catalysts (driers) on the in-depth drying of alkyd coatings. Therefore
we have studied the effect of cobalt as a primary drier combined with Ca and Zr as secondary driers on the
in-depth curing of high solid solvent-borne alkyds. The profiling of the curing of alkyd coatings is performed
with a new high-spatial-resolution NMR setup. In this study, two effects observed in the solvent-borne alkyd
coatings are investigated. One is that when Ca and Zr are added as secondary driers the speed of the observed
cross-linking front increases. Second, in the deeper un-cross-linked region below the front, the signal of the
NMR profiles was found to decrease proportional to xt. This could be explained by the presence of slowly
reacting species that diffuse into the deeper uncured region of the coating, after which they cross-link. The
model describing the effect of these reactive species also indicates that the signal decrease is inversely
proportional to coating thickness L, which was confirmed by additional measurements.