Thermo-oxidative degradation kinetics of renewable hybrid polyurethane–urea obtained from air-oxidized soybean oil

This study explores the synthesis and kinetics of non-isothermal thermo-oxidative degradation of renewable hybrid polyurethane (PU)–urea obtained from air-oxidized soybean oil. Fourier transformed infrared spectroscopy (FTIR) and thermogravimetry (TG) analyses were performed, aiming to verify chemical changes and the kinetics parameters using different approaches for the samples obtained. FTIR confirmed that a polymerization process occurred as well and modification in the relative hydrogen bonds is due to the formed urea groups that formed in the hybrid materials. TG analysis showed a dependence of the activation energy (using the FWO and KAS model-free methods) on the degree of conversion for all samples studied in three different degradation steps. The most probable degradation mechanism was tested by using a multivariate nonlinear regression by using the F statistical test. For all samples, the autocatalytic model successfully described the thermo-oxidative degradation, which is in accordance with the chemical degradation process for polyurethanes. Finally, thermal degradation in the time function was estimated and more satisfactory results were obtained by comparing the literature data for similar systems. So, it was possible to obtain reliable and consistent results of the kinetic parameters, which are essential for academic and industrial purposes.