The composition of the pyrolysis products of plastics depends on disintegration of the macromolecule into variety of hydrocarbon fractions. In this work, a detailed gas chromatographic study of pyrolysis products of polypropylene (PP) between 200 and 600 degrees C was carried out. The pyrograms have been analyzed in terms of amount of different products evolved at various pyrolysis temperatures. At low pyrolysis temperatures (200-300 degrees C), the yield of lighter hydrocarbons (C5-C10) is low; it gradually increases until maximum decomposition temperature (446 degrees C) and decreases thereafter. The following reaction types were considered to explain the decomposition mechanism of PP: (a) main chain cleavage to form chain-terminus radicals; (b) intramolecular hydrogen transfer to generate internal radicals; (c) intermolecular hydrogen transfer to form both volatile products and radicals; and (d) beta-scission to form both volatiles and terminally unsaturated polymer chains. VC 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119:2318-2325, 2011