Synthesis and Characterization of a New Thermoreversible Polyurethane Network

A new polyurethane network was synthesized by the Diels-Alder cross-linking reaction of a polyurethane to bisfuryl monomer. Attenuated total reflectance in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR) spectra of the network showed the disappearance of the absorption bands of maleimide and the appearance of new bands attributed to furan-maleimide cycloadduct. Chemical shifts characteristic to the cycloadduct appeared in the proton nuclear magnetic resonance spectra. ATR-FTIR and differential scanning calorimetry (DSC) demonstrated the thermal reversibility of the material by the reproduction of the retro-Diels-Alder and Diels-Alder processes upon heating and cooling. Global kinetic nonisothermal decomposition parameters in nitrogen were determined by the Flynn-Wall-Ozawa method. A three successive stage thermal decomposition mechanism depicted by n order reaction model for each stage was proposed. The validity of the chosen kinetic model and the values of the kinetic parameters of the individual decomposition stages were determined by the multivariate nonlinear regression method.