The thermal properties of silver powder-filled polypropylene composites were studied as a function of filler concentration. Thermal conductivities of the composites increased with filler content. Comparison of the data with theoretical predictive models for two-phase systems showed that the Nielsen equation agreed reasonably well with the measured values. A TGA study showed that presence of silver powder increased the thermal stability of polypropylene through an increase in activation energy. The thermal expansion coefficient of the composites exhibited a decrease in the presence of Ag powder. Surface treatment of Ag powder with a titanate coupling agent marginally increased thermal conductivity and decreased thermal expansion coefficient values, implying a degree of enhance adhesion of the filler with the polymer. 1994 John Wiley & Sons, Inc.