The effects of physical aging of a 75 : 25 PC/ABS blend have been Studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). From DSC, two distinct peak endotherms at about 90 degrees C and 110 degrees C, which are associated with the glass transition of ABS (T-g,T-ABS) and PC (T-g,T-PC) components, respectively, were observed. When progressive aging,vas monitored at 80 degrees C for over 1000 h, the changes in enthalpic relaxation, glass and fictive temperatures for the blend followed similar trends to those already seen in the literature for PC aged between 125 and 130 degrees C. The rate of enthalpy relaxation was also comparable. The plot of peak endotherm against logarithmic aging time for the PC blend constituent, however, behaved quite differently from the linear relationship known for highly aged PC. The ABS peak component also appeared to be insensitive to aging. Both observations were confirmed to be statistically significant using analysis of variance methods. Using temperature modulated-DSC, there is evidence that aging increases the blend miscibility as the T-g,T-PC shifts toward the stationary T-g,T-ABS during aging. Parallel FTIR investigations found oxidation of butadiene during aging to be even at this relatively low temperature, forming hydroxyl and carbonyl degradation products. The presence of ABS in the blend also appeared to have prevented the shifting from the trans-cis to trans-trans arrangement of the carbonate linkage, which is a well-known phenomenon during elevated temperature aging of PC alone. Moreover, the carbonate linkage appears to have been at the lower energy, transtrans, arrangement prior to the aging process. (C) 2008 Wiley Periodicals, Inc.