The efficiency of the assessment and of the development of energetic materials can be increased by modelling stability, compatibility, ageing and thermal decomposition of the used components and formulations. All four terms have in common that chemical reactions are the dominating processes, besides for example migration of mobile components. These chemical reactions are only in part controlled by thermodynamics, to a great extend they are controlled kinetically. Kinetic models are formulated and used for mass loss measurements with isothermally operated ovens and TGA (Thermogravimetric Analysis). The models include autocatalytic decomposition and evaporation or decomposition of a minor component beside a main component. A formulation of a general bimolecular reaction in terms of mass loss is useful in compatibility studies. Approximations and simplifications of the autocatalytic models are discussed. The shown applications include new data on hexanitrohexaazaisowurtzitane crystallized in epsilon-phase (E-HNIW, epsilon-CL20) and rocket propellant formulations of type HFK containing epsilon-CL20 as main component. The kinetic data for the decomposition of epsilon-CL20 are given and discussed with data from literature.