Minor amounts of a fully exfoliated PA6/commercial OMMT nanocomposite were used as a master-batch to produce exfoliated PA6,6 based nanocomposites. The major component PA6,6. which was fully mixed with PA6, did not largely affect the interactions between the OMMT and the surrounding polymer, as the exfoliation level of OMMT increased upon blending with PA6,6. Both the phase behaviour and the mechanical properties of the nanocomposites were compared with those of the PA6,6-rich matrix, to assess the separate effects of the PA6 and the OMMT. The large exfoliation level attained, led to increases in the modulus of elasticity that reached 46% with 5 wt% OMMT, and to the presence of highly ductile materials up to 3 wt% OMMT content. (c) 2005 Elsevier Ltd. All rights reserved.