GPC and structural analysis of polyurethane degradation

Linear polyurethane (PUR) prepolymers were synthesized starting from diphenylmethane-4,4′-diisocyanate (MDI) and polyester diol oligomers. Two different types of polyester diols were used: poly(ethylene adipate) (PEA) and poly(ethylene/butylene adipate) (PEBA). The effects of UV irradiation on the photooxidative degradation of prepared PUR prepolymer were studied.

The changes in the chain lengths and their distribution as well as the changes in chemical structure were followed. The GPC results show that the photooxidative decomposition is followed by a decrease in molecular mass together with an increase in polydispersity. This indicates a very inhomogeneous degradation, which is a consequence of the specific course and of the intensity of photooxidative degradation. This was confirmed by means of comparative IR and NMR measurements. Conclusions on the difference in behaviour of the two different types of polyester diols used in PUR synthesis were discussed.