Ultrasonic motors (USMs) are driven by friction forces between a stator and rotor. So the output properties and life of USMs are strongly related to the properties, such as the mechanical and tribological properties, of the frictional materials. In this study, the effects of the content of potassium titanate whiskers (PTWs) on the mechanical and tribological properties of polytetrafluoroethylene (PTFE)-based friction materials and the performances of the corresponding USMs were studied. The morphology of worn surfaces of PTFE composites were observed with a scanning electron microscope. The experimental results show that the PTWs not only increased the hardness and elastic modulus of the PTFE composites but also increased the friction coefficient and wear resistance of the PTFE composites. On the whole, the PTFE-based friction materials filled with 5 wt % PTWs were the preferable friction materials for USMs. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012