Ethylene–(vinyl alcohol) (EVOH)/organo-modified montmorillonite clay (OMMT) composites were prepared using commercial OMMTs with two different organo-modifiers. The first one has polar groups, which interact with EVOH chains, whereas the second one is non-polar. Composites with a high weight percentage of OMMT were prepared bymelt-extrusion in a twin-screw extruder. Films were prepared in a cast-film line in order to evaluate the tensile and fracture parameters. The morphology of the EVOH/OMMT composites was characterized using wide-angle X-ray scattering and transmission electron microscopy, complemented by image analysis. Themechanical propertieswere evaluated using uniaxial tensile tests; the fracture behaviour was analysed using the essential work of fracture (EWF) method. Results show differences in composite morphologies and crystalline fraction, depending on the content and the nature of the organo-modifier. The mechanical and fracture behaviours are strongly influenced by those parameters,which act in opposite senses. The EWFmethod is shown to be a useful tool for the analysis of the structure–properties relationships of these composites.

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