Isothermal and dynamic thermogravimetric analysis (TGA) were performed on a polycyanurate thermosetting material. The effects on thermal stability of the copper naphthenate catalyst were studied by comparing two systems with different amounts of catalyst. Tests were performed isothermally at temperatures ranging from 200 degrees C to 240 degrees C for times up to one week. Dynamic tests were also performed at rates from 0.1 degrees C/min to 40 degrees C/min at temperatures ranging from 180 degrees C to 600 degrees C. It is found that increasing the concentration of copper increased the weight loss in isothermal tests, but did not affect the overall activation energy. Conversely, in dynamic tests, copper concentration had no effect on weight loss. The results demonstrate the difficulties of extrapolating dynamic TGA data to use conditions in order to predict long-term thermal stability.