Conventional and chain extended-modified solid-state polymerization (SSP) of postconsumer poly(ethylene terephthalate) (PET) from beverage bottles was investigated. SSP was carried out at several temperatures, reaction times, and 2,2'-bis-2-oxazoline (OXZ) or pyromellitic anhydride (ANP) concentrations. The OXZ was added by impregnation with chloroform or acetone solution. Higher molecular weights were reached when the reaction was carried out with OXZ, resulting in bimodal distribution. The molecular weights of the flakes reacted at 230 degrees C for 4 h were 85,000, 95,000, and 100,000 for samples impregnated with 0, 0.5, and 1.25 wt% OXZ solution, respectively. In the case of reactions with ANP, branched chains were obtained. The thermal and thermal-mechanical-dynamic properties of these high-molecular-weight recycled PET were determined. For OXZ-reacted samples, the reduction of crystallinity was observed as the reaction time was increased, becoming evident the destruction of the crystalline phase. The chain extended samples did not show changes in thermal relaxations or thermal degradation behavior. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 3177-3188, 2010