Determination of activation energy for glass transition of an epoxy adhesive using dynamic mechanical analysis

The activation energy associated with the glass transition relaxation of an epoxy system has been determined by using the three-point bending clamp pr ovided in the recently introduced TA Instruments DMA 2980 dynamic mechanica l analyzer. A mathematical expression showing the dependency of modulus mea surements on the sample properties and test conditions has also been derive d. The experimental results showed that the evaluation of activation energy is affected by the heating rate and test frequency, as well as the criteri on by which the glass transition temperature (T-g) is established. It has b een found that the activation energy based on the loss tangent (tan delta) peak is more reliable than on the loss modulus (E-2) peak, as long as the d ynamic test conditions do not cause excessive thermal lags.