New techniques for determining the extent of crosslinking in coatings

Crosslinking reactions in latex and alkyd systems offer an attractive way to achieve film formation at low temperatures while also achieving a final hard coating. There is a strong need for techniques to characterise the extent of crosslinking as a function of time and depth in this type of coating. Here magnetic resonance imaging (MRI) (using a magnet specifically designed for coatings) and a quartz crystal microbalance with energy dissipation are both used as non-invasive techniques for this purpose. The crosslinking in alkyd films containing a cobalt drier is found to be non-uniform with depth. In a latex, crosslinking depth profiles are likewise non-uniform, most likely as a result of oxygen inhibition of the initiator. (C) 2001 Published by Elsevier Science B.V.