Thermoplastic polyurethane (TPU)-clay nanocomposites were studied with respect to thermal properties and morphology. Different types of clay, e.g. modified laponite (ionic followed by covalent modification using different silanes) and montmorillonites (e.g. Cloisite 30B and Nanomer I.30E) were used. Activation energies (E) for thermal decomposition of nanocomposites were determined by Flynn and Wall technique. The changes in 'E' value with the level of conversion suggest a complicated degradation rate. Lifetime of composites was estimated by Toop's equation revealing higher lifetime for montmorillonite based composites. It was found that dual modification of laponite was sometimes more effective/equivalent to commercial montmorillonites regarding viscoelastic properties and thermo-dimensional stabilities of nanocomposites. Phase morphology, filler dispersion, RMS roughness obtained from SEM (including X-ray dot mapping), AFM analyses revealed the role of aggregates in degradation of properties of composites. Moreover, thermo-physical properties were dependent on the aspect ratio, polarity, and aggregation characteristics of clay into TPU. (C) 2010 Elsevier B.V. All rights reserved.