Plastic is one of the most commonly used materials today, used in many applications. Due to the widespread use of plastic, much of that same plastic ends up in municipal waste. Plastic waste can be successfully mechanically and chemically recycled. Problems of recycling occur with multilayer plastic packaging as it consists of multiple layers of different types of polymers, which cannot be separated. Due to the energy recovery of such laminate foils has been proven to be a justified way of recycling. In this paper, we used polymeric materials obtained from the Rotoplast company that are used for the production of packaging, these were foils based on poly(ethylene terephthalate) (PET); PET-PE (metallized), PET-boPP, APET-PE and PET-PE (laminated). Thermal stability was tested by thermogravimetric analysis (TGA) at four different heating rates; 5, 10, 15 and 20 ° C/min with and without the presence of the catalyst (NiCl2). The temperatures at the maximum decomposition rate (Tmax), the temperatures of the started decomposition (T90), the maximum decomposition rates (rmax) and the mass of the char residue (mr) were determined for the samples. Using the Kissinger-Akahira-Sunose (KAS) isoconversion model, the activation energies (Ea) of thermal decomposition were determined for all studied samples and for both system investigations, without and with a catalyst. From the obtained results it can be concluded that NiCl2 was a suitable catalyst in the processing of polymer laminate films with higher PET content as it contributed to decomposition at lower temperatures and lower activation energy thus making pyrolytic process more efficient.