The pyrolysis of the amorphous copolyester poly(ethylene glycol-co-cyclohexane 1,4-dimethanol terephthalate) (PETG) was investigated. The applied technique was thermogravimetry/differential scanning calorimetry/mass spectrometry analysis. The pyrolysis products of PETG were ascertained. The results showed that the PETG mass loss was 90.36% from room temperature to 650 degrees C, its thermal decomposition was mainly completed in one step at 425.2 degrees C, and the aliphatic backbone of PETG played a dominant role in controlling the behavior of the pyrolysis. The pyrolysis mechanism was also examined. (c) 2006 Wiley Periodicals, Inc.