Thermal decomposition analysis and combustion mechanism investigation of biomass-based polyurethane

Starch phosphate carbamate was synthesized via a one-pot method using phosphoric acid, urea and starch, and it was added into polyurethane (PU) to replace some polyol. The fire retardancy and thermal stability of the resulting PU system were evaluated by the results of vertical burning test (UL-94), limiting oxygen index (LOI), cone calorimeter (CONE) test and thermogravimetric analysis. Raman spectroscopy and X-ray photoelectron spectroscopy were used to analyze the char layer after the CONE test, and the thermogravimetric–infrared test was used to analyze the gas products at the maximum rate of thermal decomposition. The introduction of 13.7 wt% starch phosphate carbamate (PU-15) in PU enables the system to pass the V-0 rating, with LOI reaching 22.8%. The peak heat release rate of PU-15 decreased by 36.54% compared to PU, and the total heat release of PU-15 was only 27.87 MJ m⁻². Starch phosphate carbamate reduces the generation of combustible small molecules during the combustion of the system, producing a more protective char layer. Raman results indicate that starch phosphate carbamate can increase the stability of the char layer. Integrating the results from various tests, the combustion mechanism of PU with starch phosphate carbamate was explored. Starch phosphate carbamate provides a new approach for preparing high-performance PU. © 2024 Society of Chemical Industry.