Quantitative characterization of alkyd cure kinetics with the quartz crystal microbalance

The quartz crystal microbalance (QCM) was used to measure the time-dependent mechanical properties of an alkyd resin throughout the transition from its application as a liquid to the formation of a solid film. Three different regions of curing were observed, corresponding to solvent evaporation; early stage curing, where the mass increases as oxygen is incorporated into the film; and long-term curing, where the mass decreases as volatile compounds are released. Mechanical property changes obtained at 15 MHz with the QCM were correlated with measurements at much lower frequencies utilizing traditional dynamic mechanical analysis. These mechanical property changes were in turn correlated to chemical changes tracked with Raman spectroscopy. From the temperature dependence of the curing process we obtain an effective activation energy of 4.1 kcal/mol.