Abstract
Epoxy resins are widely used as adhesives or as the matrix of high-performance composites and the monitoring for quality of their cure process is of great interest. In this paper, the cure kinetics of an epoxy/polyamide system was successfully studied using the dynamic torsional vibration method (DTVM) by measuring the change in mechanical properties (torque) during the cure. The experimental data were analyzed by the non-equilibrium thermodynamic fluctuation theory and the Avrami method. The results from dynamic mechanical thermal analysis (DMTA) reveal that the fully cured specimens of epoxy resin/polyamide exist in the rubbery plateau state at the applied cure temperature. With increasing cure temperature, the equilibrium torque drops, the gel time decreases and the cure reaction takes less time to complete. After the gel point, the same curing mechanism occurs at various cure temperatures. The effect of increasing hardener concentration on the rate of cross-linking at a given cure temperature was also examined. Excess polyamide increases the number of cross-linking points, and hence enlarges the Avrami exponent n.
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