Starting with a short summary about chemical and physical fundamentals of different interlayer materials, this article gives an overview about the thermal stability of these analyzed materials. Interlayer of polyvinyl butyral (PVB) as well as ionomers like SentryGlas (SG) are subjects of this investigation. Due to the chemical structure, the materials show differences in their thermal stability and their degradation processes. The decomposition behaviour will be characterized by thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) to analyze and identify the envolved gases from constituents volatilized during thermal stress. Such analyses give information about changes in the optical and mechanical properties of the polymeric interlayer, which can occur in cases of a permanently raised temperature and cause discoloration, delamination or blistering of the interlayer.