Polyetheretherketone (PEEK) is an aromatic polyketone and commonly used as an engineering thermoplastic materials composed of ketone and aromatic moieties with a high thermal stability, chemical and radiological resistance. It is used in many high performance applications due to its properties, such as in implant materials, aerospace, automotive industries, power and energy generation. In this application, we study the thermal decomposition of PEEK in inert and oxidized atmosphere by Thermo Mass Photo.