In this study, a series of segmented polyurethanes based on 4,4'-diphenylmethane diisocyanate (MDI), polyoxypropylenediol (POPD) and low-molecular chain extenders: 1,2-propanediol (PD) or 3-chloro-1,2-propanediol (CPD) has been obtained by one-step polyaddition. The thermal properties were investigated by thermogravimetric method in both isothermal and dynamic mode. The relation between the amount of 3-chloro-1,2-propanediol in the polyurethane's structure and the maximum temperature of first derivative of thermogravimetric analysis (TG) profile (DTG) has been described. For further characterisation of the thermal behaviour of modified polyurethanes under investigations thermogravimetric analysis coupled with Fourier-transform infra-red (FTIR) spectroscopy or mass spectrometry (MS) were used. The main decomposition products, including CO2, amines and aliphatic ethers, were identified on-line. Comparison of the intensity of evolution of [CH2 = NH2](+) ion (m/z = 30), which can be associated with primary amines, has shown that there is a correlation between the amount of chlorine in PU structure and the intensity of amines' formation during the main decomposition step around 300degreesC. (C) 2003 Elsevier B.V. All rights reserved.