Temperature programmed co-pyrolysis of low-density polyethylene (LDPE) with polypropylene (PP) was investigated. The aim of this research was to determine the volatile product distribution and product evolution rate of co-processing of LDPE with PP. A series copyrolysis operation was performed with LDPE and PP using a 1 3, 1:1, 3:1 total carbon ratio of LDPE to PP. A fixed bed reactor was used to pyrolyse small sample of LDPE and PP mixture under an inert gas flow (argon). A special sampling technique was used for collecting organic products eluted from the reactor at different temperature and time intervals. The co-pyrolysis products were analyzed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. n-paraffins and 1-olefins in aliphatic fraction of co-pyrolysis products were classified as a carbon number. In addition, the recovery of total organic carbon as an organic volatile product was determined. The assessments were based on incorporating the results on temperature-programmed pyrolysis of LDPE and PP. The effect of co-processing of LDPE with PP was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. Conversion into volatile hydrocarbons was found to be higher, with the increasing PP ratio in the co-pyrolysis operation. (C) 2001 Elsevier Science Ltd. All rights reserved.