Investigation on the thermal decomposition of hydroxyl terminated polyether based polyurethanes with inert and energetic plasticizers by DSC-TG-MS-FTIR

Thermal decomposition behavior of hydroxyl terminated polyether (HTPE) based polyurethanes (PUs) containing glycerol triacetate (TA), bis(2,2-dinitropropyl)-acetal/formal (BDNPA/F, also known as A3) and N-butyl-N-(2-nitroxyethyl)nitramine (NENA) respectively as plasticizers were investigated by the combination of differential scanning calorimetry-thermogravimetry-mass spectrometry-Fourier transform infrared spectroscopy (DSC-TG-MS-FTIR) techniques. Instead of DSC, DTG curves were applied to evaluate the compatibility since no intense exothermic effect appears in decomposition of HTPE based PU. Three plasticizers, especially the inert TA, were absolutely compatible with HTPE in perspective of engineering application according to the evaluated standard of compatibility. Decomposition of HTPE based PU after endothermic melting is a two-step process including, exothermic depolymerization succeed by intense decomposition. Influence mechanisms of energetic and inert plasticizers on decomposition of HTPE based PU are different. NO· free radical generated by the pyrolysis of NENA and A3 is the major incentive of chain scission resulting in depolymerization of HTPE based PU, and chain scission temperature are shifted forward with the increasing concentration of NO· as the NENA-PU is more vulnerable. While carbanion and electrophile intermediate resembling CO₂ generated by decarboxylation reaction of carboxylic acid are the major reactive products in TA. Furthermore, micro defect caused by migration of TA in TA-PU accelerates the degradation of HTPE based PU under acidic condition.