A poly-epsilon-caprolactam (PA6) taken as a reference and its nanocomposite (PNC) containing 1.6 wt.% of montmorillonite were examined. The specimens as discs were prepared by compression moulding at 235degreesC and 70 MPa. Using the novel version of TMA, in the PA6 and PNC specimens, within the temperature range from -100 to 250degreesC, a semi-crystalline structure with anisotropy of distribution of the more ordered (crystalline?) portion was found in the surface layer up to 0.5 mm thick. The amorphous regions have differed in a state of order (different transition temperatures) and related compactness. The free volume fraction in amorphous regions determined in machine direction (normal to the surface) is increased when in transverse direction is reduced; Simultaneously Molecular weights of polymer chains between junctions were increased by incorporation of the nanofiller. (C) 2004 Elsevier B.V. All rights reserved.