The design of multi flame-retarding elements towards the enhance the flame retardancy and mechanical property of rigid polyurethane foam

Rigid polyurethane foam (RPUF), widely utilized as a thermal insulation material, presents considerable fire safety concerns. The combustion of RPUF generates significant heat, which poses serious risks to both human health and the environment. In an effort to improve the flame retardancy of RPUF while preserving its thermal insulation and compressive properties, this research introduced a novel flame retardant, DOPO-AZ, synthesized from 9,10-dihydro-9-oxa-10-phenanthrene-10-oxide (DOPO) and 2-aminothiazole (AZ). The incorporation of 17 wt% DOPO-AZ into RPUF resulted in the composite achieving a UL-94 V-0 classification, with the limiting oxygen index (LOI) increasing from 19.5 % to 24 %, and a reduction of 27.9 % in the peak heat release rate (PHRR) compared to pure RPUF. This study successfully enhanced flame retardancy while maintaining the thermal conductivity of RPUF at 0.034 W/(m·K), comparable to that of pure RPUF, and significantly improved its compressive strength by 25.8 %. The synergistic flame-retardant mechanisms of the RPUF/DOPO-AZ17 composite in both condensed and gas phases were elucidated through scanning electron microscopy (SEM), thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR), and Raman spectroscopy, thereby providing a theoretical basis for the future design of more effective flame-retardant systems. [Display omitted]