| Abstract: | The thermal dissociation of urethane groups has been studied by FTIR spectroscopy depending on the type of diisocyanate, the structure of the hard segment and the composition of polyurethane. Independent of the composition and the structure, the dissociation started between 150 and 160°C. Consequently, the dissociation sets in at temperatures below the melting temperature of the model hard segments, i.e. already in the solid state. The NCO absorption band reaches its maximum intensity between 180 and 190°C. This result opposes the references in literature suggesting a four-centre reaction for transurethanization. |
