The effect of different thermal treatments on the mechanical and thermal properties of polycarbonate was investigated. The first quenching procedure which involves the quench of the samples from the melt state to different temperatures allowed improving impact strength and elongation at break for a quenching temperature of 0 degrees C. A second quenching procedure, corresponding to specimens heated again at 160 degrees C (T-g + 15 degrees C) and quenched a second time, showed a better enhancement of the impact strength and elongation at break to the detriment of other properties such as elastic modulus, density, yield stress, and heat distortion temperature, for a quenching temperature of 40 degrees C. This effect was associated to the existence of a relaxation mode around 35 degrees C. (C) 2008 Wiley Periodicals, Inc.