IKP and E (2) function methods were used to study thermal stability of HDPE-HA nanocomposites synthesized by in situ ethylene polymerization at different volumes of solvent and temperatures. Thermal analysis was carried out at five different heating rates, beta = 3, 5, 7, 10, and 13 A degrees C/min, under N-2 atmosphere. Kinetics parameters calculated by IKP method presented a slight increase on activation energy when HA was incorporated in HDPE. A similar tendency was observed in the results obtained from the E (2) function method, where the activation energy of the nanocomposites increased 100 kJ/mol with respect to unfilled polymer (420-460 kJ/mol). These results implied higher stability of HDPE due to HA incorporation. HDPE and HDPE-HA degradation mechanisms are represented by a set of functions, those with the highest probability were: nucleation and nucleus growth (S3) 23 %, reaction order (S5) 16 %, reaction in the interface (S6. S7, S8) 11-14 %, and potential law (S14, S17) 3 %.