Poly(ethylene terephthalate) (PET) resins were air stripped at temperatures from 160 to 190 degrees C to monitor changes that occur during reduction of residual acetaldehyde (AA) concentrations. During this process diffusion and generation of AA, 2-methyl-1,3-dioxolane (2MD), ethylene glycol (EG), and water occurred as the molecular weight and crystallinity increased through complex chemical reactions involving polymerization, formation of by-products, and some degradation at higher temperatures. This process was characterized in terms of time and temperature of stripping, with determination of residual concentrations of AA and other less volatile compounds such as 2MD and EG. Residual AA concentrations continually decreased from their initial values, while concentrations of 2MD decreased initially, then increased, and later decreased with time. Empirical rate constants for resin solid-state polymerization were determined at the air-stripping temperatures, and free EG concentrations as well as intrinsic viscosity, density, crystallinity, and color were monitored to aid in studying the kinetics of AA removal. POLYM. ENG. SCI., 2012. (C) 2012 Society of Plastics Engineers