Thermal degradation of polyurethane based on MDI and propoxylated trimethylol propane

A polyurethane based on diphenyl methane diisocyanate (MDI) and propoxylated trimethylol propane was thermally degraded by using the techniques of pyrolysis and thermogravimetric analysis (TGA) in an inert atmosphere. Identification of pyrolysis gaseous products at 600°C showed that the first degradation step consists of a reversal of the polycondensation process, i.e., dissociation into starting polyol and diisocyanate, followed by the polyol degradation and a probable diisocyanate polymerization. Kinetic parameters were determined using dynamic and isothermal TGA curves. It is shown that the degradation can be closely compared with a random chain scission process.