IMPEDANCE SPECTROSCOPY OF REACTIVE POLYMERS .3. CORRELATIONS BETWEEN DIELECTRIC, SPECTROSCOPIC, AND RHEOLOGICAL PROPERTIES DURING CURE OF ATRIFUNCTIONAL EPOXY-RESIN

An investigation was carried out of correlations between dielectric, v ibrational spectroscopic, and theological properties during cure of a thermoset formulation composed of trifunctional epoxy resin and tetraf unctional amine. Experimental techniques utilized include impedance sp ectroscopy, near-infrared spectroscopy, steady shear, and dynamic mech anical measurements. Reaction kinetics obtained from dielectric and sp ectroscopic results were in excellent agreement. Gelation and vitrific ation times determined by dielectric and theological measurements were also found to agree very well, despite the empirical nature of such c orrelations. A characteristic pattern in plots of imaginary impedance as a function of reaction time was reported for the first time in the open literature, and it was suggested that it could be used to identif y gelation and vitrification during the network formation. A realizati on of the full potential of dielectric impedance spectroscopy in monit oring the progress of chemophysical changes in reactive polymers, howe ver, hinges upon a development of fundamental scientific correlations between dielectric and chemorheological phenomena during cure. (C) 199 6 John Wiley & Sons, Inc.