In this study, a detailed gas chromatographic study of pyrolysis products of polyethylene terephthalate (PET) has been carried out over a wide range of temperature (200-600 degrees C). At low pyrolysis temperatures (200-300 degrees C), yield of lighter hydrocarbons (C5-C10) is low; this gradually increases until maximum decomposition temperature (435 degrees C) and decreases thereafter. At low temperature, PET essentially decomposes by ionic mechanism. However, at higher temperature, it may also proceed by radical mechanism. The following reaction types were considered to explain the decomposition mechanism of PET: (a) heterolytic (ionic) main-chain cleavage to form an olefin-end and an acid-end structure; (b) intra- or intermolecular ester-interchange reactions to yield cyclic oligomers; (c) intramolecular hydrogen transfer to form volatile products and regeneration of the acid-ends or, olefin-ends; (d) decarboxylation and intramolecular elimination of acetaldehyde, and acetylene; and (e) hydrogen abstraction and acetylene addition mechanism for the formation of polycyclic aromatic hydrocarbons. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3993-4000, 2013