Through this work we explored the effect of melt compounding a commercial grade of HDPE with organoclays of different precedence using EMAA as compatibilizing agent on the thermal behavior, barrier properties and biaxial impact response of composites. Morphology was examined by XRD and TEM. Crystalline structure was examined by DSC. Thermal behavior was evaluated by TGA. Barrier properties to low-molecular-weight penetrants were experimentally determined employing a gravimetric technique. Mechanical properties under impact conditions were evaluated by instrumented puncture tests. Intercalated nanocomposites were obtained. Throughout the thermal degradation of the nanocomposites in oxidant atmosphere a charring process of the PE, which is normally a non-char-forming polymer, was observed. The addition of OMMT improves barrier properties due to its contribution to tortuosity path and to the reduction of molecular mobility. Impact properties were only slightly reduced by nanocomposite formation. Results demonstrate that EMAA did not improve exfoliation, but it enhanced polymer-organoclay interactions giving rise to better thermal and permeation properties, without detriment of impact response. (C) Koninklijke Brill NV, Leiden, 2009