Silica nanoparticle-filled poly(ethylene 2,6-naphthalate) (PEN) composites were melt-blended to improve the mechanical and theological properties of PEN. The melt viscosity and total torque values of the composites were reduced by the silica content. The crystallization exothermic peak shifted to a higher temperature, and the overall crystallization time was reduced by increasing the silica content. Non-isothermal crystallization kinetics was analyzed using the Ozawa and Avrami theories, and a combined method. The combined method was successful in describing the non-isothermal crystallization of these composites. The crystallization activation energy calculated using Kissinger's method was reduced, and the spherulite growth rate increased, with increasing silica content.A study of the nucleation activity, which indicated the influence of the filler on the polymer matrix, revealed that the fumed silica nanoparticles had a good nucleation effect on PEN. (C) 2003 Elsevier Ltd. All rights reserved.