Experimental and numerical study on pyrolysis kinetics and thermodynamics of the polymer core in rigid polyurethane foam sandwich insulation materials

To quantitatively characterize the pyrolysis behavior of rigid polyurethane foam core (RPUc) in sandwich insulation panels, a systematic methodology is proposed that combines thermoanalytical experiments at the milligram scale with the COMSOL Multiphysics reaction engineering module to analyze pyrolysis kinetics and thermodynamics. Mass loss profiles obtained from thermogravimetric analysis (TGA) enable the development of multi-step pyrolysis reaction mechanisms and the determination of stoichiometric coefficients, preexponential factors, and activation energies for each pyrolysis reaction via inverse modeling. A hill-climbing optimization algorithm was employed to obtain the optimal kinetic parameter set. In addition, heat flow results from differential scanning calorimetry (DSC) allow the determination of condensed-phase heat capacities and pyrolysis reaction enthalpies through inverse modeling, facilitating the development of a comprehensive pyrolysis reaction model. The results demonstrate that a five-step consecutive first-order lumped reaction mechanism successfully captures the mass loss and heat flow evolution of RPUc during pyrolysis and accurately predicts its mass loss behavior under different heating rates. The integrated methodology proposed in this study demonstrates broad applicability and can also be applied to determine the pyrolysis characteristics of combustible solids in fire-retardant sandwich panels and multi-layer polymer materials.