Thermal decomposition of mixtures of vinyl polymers and lignocellulosic materials

The effect of wood, cellulose, lignin and activated charcoal on the thermal decomposition of polystyrene (PS) and polyethylene (PE) has been studied in order to investigate the thermal behavior of these materials occurring in municipal waste. Thermogravimetry/mass spectrometry and pyrolysis-gas chromatography/mass spectrometry revealed that these materials had a similar influence on PS and PE thermal decomposition under slow and fast heating conditions respectively. The effect is related to the char-forming capability of the wood-derived additives; thus cellulose had the least and pure charcoal had the greatest influence on the decomposition of the polymers studied. Polystyrene is more sensitive to the presence of additives than the two PE polymers investigated. The thermal decomposition of PS shifts to higher temperature and the product distribution changes significantly in the presence of wood-derived additives. The yield of monomer, dimer and trimer decreases and the formation of other products (e.g. toluene, ethyl benzene and cl-methyl styrene) increases. The effect of additives is interpreted in terms of the free radical mechanism of the thermal decomposition of PS. Wood, cellulose and lignin have a small effect on the thermogravimetric curves of PE. Charcoal promotes the hydrogenation of the unsaturated products and the hydrogenated products evolve at higher temperature. (C) 2001 Elsevier Science B.V. All rights reserved.