Study on the Pyrolytic Behaviors and Kinetics of Rigid Polyurethane Foams

In order to investigate the pyrolytic behaviors and kinetics of rigid polyurethane foams (PUFs), three samples named PUF01, PUF02 and PUF03 were synthesized with different [NCO]: [OH] ratios of 1.05, 1.1 and 2, respectively. Many techniques including thermogravimetric analysis (TGA), Fourier-transform infrared spectrometry (FTIR) and synchrotron radiation vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) were used to analyze their pyrolytic behaviors. The results show that the process of PUFs pyrolysis can divide into two stages in nitrogen atmosphere: one is from room temperature to 400, and the other is above 400 .The pyrolysis of PUFs mainly occurred at temperature between 200 and 400 . The activation energies of the copolymers at lower percent conversion () grow with the increase of the isocyanate index. The higher activation energies were obtained at higher isocyanate index. Mass spectra of pyrolytic products evolved at low pressure indicate that the fission of main chain of polyurethane macromolecules leads to the formation of primary product of isocyanate. Along with the increase of temperature, the chief breakage of polyurethane occurs in the bonds of C-O and C-N. Kinds of pyrolysis products reduce with the increase of isocyanate index.