Polycarbonate (PC) and PC modified by polyacrylate/TiO2 composite particles were exposed both in an outdoor environment with typical humid and hot climatic conditions in the Jiangjin area and in an indoor hygrothermal environment for accelerated aging. Then, the effects of the polyacrylate/TiO2 composite particles on the antiaging performance of PC were investigated by measurement of the mechanical properties of PC before and after aging. The results show that the mechanical properties of PC decreased a lot after aging by the outdoor environment of the Jiangjin area. After accelerated aging by the indoor hygrothermal environment, the tensile strength and the bending strength of PC increased a little, and the elongation at break of PC decreased. The polyacrylate/TiO2 composite particles effectively increased the elongation at break of PC aged by the hygrothermal environment and outdoor aging. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 3495-3500, 2009