Dynamic dielectric analysis - A means for process control

Abstract

The development of dynamic dielectric analysis techniques (as a 'smart' sensor for quantitative NDE) and of intelligent closed-loop cure systems is reported. The cure process of both BF3:R-catalyzed and uncatalyzed tetraglycidyl-4,4'-diaminodiphenyl methane (TGDDM)/diamine epoxy resins was studied. Measurements were made over a frequency range of six decades. The resin was monitored continuously throughout the cure process as it changed from a viscous liquid to a highly crosslinked solid. From the frequency dependence of the dielectric loss, the specific conductivity has been determined and shown to directly monitor the viscosity before the gel point is reached. Dielectric master plots of the cure process, analogous to time-temperature superposition plots for rheological data, have been developed.