Thermooxidative studies of poly(ether-esters) 1.: Copolymer of poly(butylene terephthalate) and poly(ethylene oxide)

To determine the thermooxidative degradation mechanism in a copolymer of poly(butylene terephthalate) and polyethylene oxide, this polymer and a model compound (diethyleneglycol dibenzoate) were subjected to degradation at 140 degrees C in an oxygen atmosphere. The degradation processes were characterised in terms of the oxygen uptake, CO/CO2 formation, the results of FTIR analysis (polymer and model compound) and the results of GC-MS, H-1 and C-13 NMR analysis (model compound only). The oxygen uptake showed that thermooxidation proceeded more rapidly in the unstabilised polymer film than in the model compound and led to relevant changes in the FTIR spectra and total embrittlement in less than 3 h. On the basis of the results an oxidation mechanism is proposed which involves the selective oxidation of the ether parts of the soft segment, leading to the formation of new ester groups and bond cleavage. (C) 1999 Elsevier Science Ltd. All rights reserved.