Characterization of a thermoset by thermal analysis techniques: Criterion to assign the value of the α‐transition temperature by dielectric analysis

Abstract

AbstractA cured thermoset composed of diglycidyl ether of bisphenol A and m‐xylylene diamine as the cure agent was studied with different thermal analysis techniques, including differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and dielectric analysis (DEA). DSC was used to measure the glass‐transition temperature and to check the absence of the heat of reaction. DMA and DEA were used to show the existence of two transitions in the temperature range of −100 to 240°C. The transition at a low temperature corresponded to the β transition. The second one, at a higher temperature, was associated with an α transition. The β transition followed Arrhenius behavior, whereas the α transition followed Vogel behavior. For an analysis of the α transition, different equations, such as the Havriliak–Negami, Vogel, and Williams–Landel–Ferry equations, were used. Important differences related to the fitting parameters were found that depended on the type of equation and the operation mode used. For this reason, a new method for calculating the α‐transition temperature was examined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2027–2037, 2005