Assessing the progress of degradation in polyurethanes by chemiluminescence and thermal analysis. II. Flexible polyether- and polyester-type polyurethane foams

The thermooxidative and thermal stability of polyether- and polyester-type polyurethane foams were investigated by non-isothermal chemiluminescence (CL), differential scanning calorimetry (DSC) and thermogravimetry (TG). In the presence of air and humidity, the effect of various routes and conditions of polyurethane ageing (induced thermally or by light) on the chemiluminescence, DSC and thermogravimetry patterns was assessed. The rate constants determined from non-isothermal thermogravimetry and chemiluminescence measurements at 250 °C and their not very pronounced dependence on the atmosphere of degradation indicated that depolymerisation of the polyurethane containing the aliphatic polyester and aromatic polyisocyanate moieties preceded or occurred in parallel with thermal oxidation. Under conditions of 50% relative humidity, samples of the polyester-type polyurethane, aged either by light or thermally, as well as specimens of the polyether-type polyurethane, aged by light, gave increased amounts of carbonaceous residue when heated in nitrogen to 550 °C.