<p>This study investigates the effect of nanoclay (NC) and alumina on improving the thermo-mechanical properties of high-density polyethylene (HDPE) and polypropylene (PP) blends, compatibilized with polyethylene-grafted maleic anhydride (pEMAH).&#xa0;The modulus of the sample containing 1.5% and 3% NC are 893 MPa and 786 MPa, respectively. The ratio of the modulus of composites to that of the matrix increase proportionally with an increase in the composition of NC for various micromechanical models studied. The fracture energy release rate for Run 1 and Run 2 start at 2.08 and 2.35 kJ m^–2 before aging, and once aged, they increase to 6.17 and 5.82 kJ m^–2. High heat on tensile samples leads to bonding in the polymer. The bonding makes a polymer firm, prevents bending and increases the tensile strength. The COMSOL models predict the tensile strength of simulated values at 27 MPa for the 1.5% NC-reinforced matrix, which is the same as the experimental tensile value. Maximum mass loss rates show an increasing trend, with heating rates for the samples containing NC. For instance, the polymer blend containing 1.5% NC has peak mass loss rates of 15% at 5°C, 26% at 10°C and 43% at 15°C as the temperature increases. Adding NC particles to the blend improves its temperature resistance.&#xa0;The activation energy found using Horowitz and Metzger plots for HDPE/PP is 113 kJ mol^–1, which increases to 141 kJ mol^–1 for the 1.5% NC blend.</p>