This work investigates the characteristics of the thermal degradation of poly(ether urethane) (E-PU) and poly(siloxane urethane) (S-PU) copolymers by thermogravimetric analysis (TGA) and thermogravimetric analysis/Fourier transform infrared spectroscopy (TG-FTIR). The stage of initial degradation for E-PU was demonstrated as a urethane-B segment consisting of 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol. Moreover, the urethane-B segment in the copolymers had the lowest temperature of degradation (ca. 200 degrees C). The degradation of E-PU was determined by TGA and TG-FTIR analyses and had three stages including seven steps. Although the soft segment of S-PU possessed the thermal stability of polydimethylsiloxane (PDMS), the unstable urethane-B segment existed in S-PU. Therefore, the initial degradation of S-PU appeared around 210 degrees C. The four stages of degradation of S-PU involved eight steps, as revealed by TG-FTIR, which identified the main decomposition products: CO2, tetrahydrofuran, and siloxane decomposition products. The imide group with high thermal stability was to replace the urethane-B segment of S-PU, which had the lowest thermal stability herein. The poly(siloxane urethane imide) (I-PU) copolymer around 285 degrees C exhibited a high initial temperature of degradation, and the initial degradation occurred at the urethane-S segment consisting of MDI and PDMS. The degradation of I-PU was similar to that of S-PU and had four stages including six steps. Moreover, the degradation region of the imide group between 468 and 625 degrees C was merged into the degradation stage of the siloxane decomposed products. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 26162628,2010