The pyrolysis of para-toluene isocyanate

Para-toluene isocyanate is a major intermediate in the pyrolysis of aromatic di-isocyanates which are widely used in polyurethane foam formulations. The pyrolysis of para-toluene isocyanate (p-TI) has been studied quantitatively in a flow system at temperatures of 823K to 873K. Qualitative data on aromatic diisocyanate pyrolysis is also interpreted in the context of polyurethane degradation to isocyanates and nitriles. The major products in the decomposition of p-TI were benzonitrile, methylbenzonitrile, phenylisocyanate, toluene and benzene. The orders of the reactions and the Arrhenius parameters for the rate constants have been determined for these major products. Reasonable mechanisms have been derived for the formation of the major gaseous products and for the deposited char, which appears to be a polymer derived from para-methylbenzonitrile. The rate constant for the initiation reaction [GRAPHICS] has been determined (in units s(-1)) as log(10)k(3) = 14.6(+/- 1.2) - 303(+/- 30) (kJ/mol)/2.303 RT. Copyright (C) 1996 by The Combustion Institute