Polymer nanocomposites based on poly (ethylene 2,6-naphthalate) (PEN) and carbon nanotubes (CNTs) were prepared by direct melt blending with a twin-screw extruder. Dynamic thermogravimetric analysis was conducted on the PEN/CNT nanocomposites to clarify the effect of CNTs on the thermal decomposition behavior of the polymer nanocomposites. The thermal decomposition kinetics of the PEN/CNT nanocomposites was strongly dependent on the CNT content, the heating rate, and the gas atmosphere. On the basis of the thermal decomposition kinetic analysis, the variation of the activation energy for thermal decomposition revealed that a very small quantity of CNTs substantially improved the thermal stability and thermal decomposition of the PEN/CNT nanocomposites. Morphological observations demonstrated the formation of interconnected or network-like structures of CNTs in the PEN matrix. The unique character of the CNTs introduced into the PEN matrix, such as the physical barrier effect of CNTs during thermal decomposition and the formation of interconnected or network-like structures of CNTs, resulted in the enhancement of the thermal stability of the PEN/CNT nanocomposites. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2008-2017, 2009