The aim of this study was to determine the influence of exfoliated silicate layers on the thermal conductivity of polypropylene nanocomposites. The correlation of thermal conductivity with the degree of exfoliation is examined and compared to common mineral fillers like talcum. The results clearly show that not only the filler content but also the size and number of the main particles (specific surface) influence thermal conductivity significantly. With respect to this, the smaller the particles and the more particles are in the matrix, the higher the increase in thermal conductivity. Compared to common fillers, the increase in thermal conductivity is considerably higher with exfoliated layered silicates and directly depends on the degree of exfoliation. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers