Energetic Characterization of Decomposing Sample Using Simultaneous Thermal Analysis

A simultaneous thermogravimetric analyzer was used to investigate the gravimetric and energetic behavior of a decomposing sample under inert atmosphere. Materials tested in the study included liquid chemicals, polymers and composite samples. Mathematical models were developed from the first law of thermodynamics to quantify the energetic characteristics of a decomposing sample. Along with the effect of evolved gas products, the temperature dependent thermal and physical properties were included in the development of the mathematical models. Models were used to obtain the heat of melting, standard heat of decomposition, heat of decomposition, and heat of gasification of the solid materials. It was determined that the heat of decomposition of a sample is different than the area difference of the apparent and sensible heat flow curves, an approach that is currently used in the literature. The standard heat of decomposition was measured and validated against the standard heat of evaporation of known chemicals. The standard heat of decomposition of a sample was found to be a constant quantity, irrespective of the sample heating rate, initial mass of the sample and the inert content (ash) in the initial mass of the sample. Thus, the standard heat of decomposition is proposed as a unique energetic property of a sample.