The effects of silver (Ag) nanoparticles on the physical properties of syndiotactic PP (sPP) were investigated concentrating on the isothermal melt crystallization behavior under shear. sPP with 5 wt % Ag nanoparticles presented higher crystallization temperature (T,) and heat of crystallization (Delta H-c) than pure sPP. At 90 degrees C, the Ag nanoparticles had little effect on the induction time of crystallization but a little increased the half-time t(1/2)) for the crystallization. At 100 degrees C, however, the induction time was decreased with increasing the Ag content and the t1/2 was decreased up to the Ag content of 0.5 wt %. DSC melting endotherms exhibited double melting peaks when crystal-lized at 90 degrees C under shear but a single melting peak when crystallized at 100 degrees C. The WAXD patterns exhibited that the presence of Ag nanoparticles did not produce any change in the crystal structure of sPP. The tensile strength of sPP is little changed up to the Ag content of 0.1 wt % but it was decreased with further addition. In addition, the introduction of less than 0.1 wt % Ag increased the elongation at break, but further addition decreased it abruptly. (c) 2008 Wiley Periodicals, Inc.