Effect of dimethylamine pyrophosphate on the mechanical, thermal decomposition and flame-retardant properties of rigid polyurethane foams

Abstract

To solve the problem of the insufficient flame retardancy of rigid polyurethane (RPUF), a new flame retardant, dimethylamine pyrophosphate (DMPY), was introduced into rigid polyurethane foam, and one-step foaming technology was used to prepare RPUF/DMPY composites. Furthermore, the thermal stability, flame retardancy, combustion characteristics, and gas-phase products were analyzed via thermogravimetric analysis (TGA), limiting oxygen index (LOI), cone calorimetry (CCT), and thermogravimetric infrared spectroscopy (TG-FTIR). The flame-retardant measurements revealed that when the DMPY amount exceeded 20 parts, the LOI of the RPUF/DMPY composites increased to above 23%, and all the samples reached the UL-94 V-0 level. In addition, the peak heat release rate and total heat release values of the RPUF-3 composites prepared with RPUF/DMPY were 192.6 kW/m² and 19.98 MJ/m², respectively, which were 35.0% and 29.1% lower than those of the pure RPUF, respectively, and significantly reduced the heat release of the RPUF composites. The analysis of char residue revealed that DMPY can effectively improve the density and graphitization degree of char residue during the combustion process of RPUF/DMPY composites, thereby endowing them with excellent flame-retardant properties. On this basis, the flame-retardant mechanism of the DMPY-based flame retardant RPUF composite material is proposed. This work provides new ideas for the development of new flame retardant PPUF composites.