Mechanism of thermal degradation of polyurethane based on MDI and propoxylated trimethylol propane

The various pathways of degradation of polyurethane based on MDI and propoxylated trimethylol propane were studied from the analysis of degradation gases sampled at various temperatures during the heating rise. From the beginning of degradation (250°C) to 400°C, we suggest that the main mechanism is the fracture of the polyurethane molecule into primary amine, carbon dioxide, and propenyl ether, the last leading to propene. Beyond this temperature, the mechanism may be reduced to a depolymerization process followed by radical breakdown of the polyol chain and by stripping and rearrangement of simple radicals, all of these giving the gaseous species obtained.