Clear and pigmented water epoxy systems: a study on the hardening kinetics on the basis of the variations of the viscoelastic moduli

The hardening reaction of a two-can water epoxy polyamide system was investigated on the basis of the variation of the viscoelastic moduli G′ and G′′. Unpigmented (clear varnish) and TiO₂ pigmented formulations, at two different TiO₂ concentrations, were taken into account. Time and frequency sweep procedures were carried out using the stress-controlled rheometer Haake RS 150. The behavior of G′ and G′′ vs time was fitted to a four-parameter asymptotic model through the whole course of the hardening process. Frequency sweep data, obtained at increasing times during the whole hardening process, were plotted to the generalized Cole and Cole behavior model and the corresponding mechanical spectra were drawn. An interpretation for some aspects of the cross-linking progress is discussed and possible future developments are briefly outlined. Received: 15 January 2000 Accepted: 13 November 2000