The Ultra high molecular weight polyethylene (UHMWPE) samples are prepared at sixteen different compression temperature-pressure combinations. Thermal decomposition behaviour of these samples is studied through Thermogravimetric (TG) analysis in the temperature region 50–600 °C at 5 °C/min heating rate, in a nitrogen environment. Through this, the compression parameters are identified where the sample shows maximum thermal stability. Further, these compression parameters are ascertained through activation energies, which are determined by adopting model fitting kinetic method (Coats and Redfern). In addition, activation energy of maximum thermally stable UHMWPE sample is determined at four different heating rates (5, 10, 15, 20 °C) by adopting five model free (Flynn-Wall-Ozawa, Kissinger- Akahira- Sunose, Starink, Friedman and Kissinger) kinetic methods. Finally, reaction mechanism, pre-exponential factor and thermodynamic parameters (change in entropy (ΔS), change in enthalpy (ΔH) and change in Gibbs free energy (ΔG)) are determined.