THE CHARACTERIZATION OF AMINE-ACTIVATED EPOXIES AS A FUNCTION OF CURE BY USING TGA FT-IR

The physical and chemical properties of cured diglycidyl ether of Bisphenol A (DGEBA) are greatly affected by the initial and final cure temperatures and cure schedule. These properties are also affected by the deviation from the stoichiometric ratio of curing agent used. Analysis of a previously cured epoxy for these parameters has usually involved large samples and an inordinate amount of time. In this work, a cured epoxy is studied as it decomposes using a combination of two analytical techniques: thermogravimetric analysis and simultaneous analysis of the evolved gases by Fourier transform infrared spectroscopy, a combination known as TGA/FT-IR. During the TGA/FT-IR experiment, evolution profiles for specific gases are obtained, as well as the normal TGA weight loss profiles. Using this information, both the cure schedule and epoxy/activator cure ratios could be established from the analysis of the cured polymer. The particular material studied, a DGEBA polymer cured using a primary cycloaliphatic diamine, showed a curing mechanism similar to that obtained using an aromatic diamine. However, the decomposition behavior of the studied sample was more reminiscent of an epoxy cured by using an aliphatic diamine system. This work demonstrates that a cured polymer can therefore be characterized in terms of both thermal history and activator-resin ratio in a single TGA/FT-IR experiment.