A novel cysteine-based flame retardant for biomass poplar wood density board

A novel reactive flame retardant based on L-cysteines containing P, N and S flame retardant elements was synthesized and used to improve the flame resistance of a density board made of poplar wood. The outcomes demonstrated the excellent flame retardancy and catalytic carbon formation of the poplar density board treated with the flame retardant. The thermogravimetric infrared coupler (TG-FTIR) test and thermal cracking gas mass spectrometer (Py-GC-MS) test both revealed that the flame retardant modified the thermal decomposition pathway of the wood, forming many residues and producing only a small amount of combustible gas. The ultimate oxygen index (LOI) of poplar density board treated with 20% cysteine-based flame retardant was as high as 60.9%. Scanning electron microscopy (SEM) images revealed that the surface of the treated wood powder was rough and that the wood powder particles were interconnected by the flame retardant. This suggests that the flame-retardant molecules have a bridging effect on the inner structure of the density board. Moreover, the cone calorimetry (CONE) experiments showed that with the flame retardant treatment, there was significant reduction of total heat release (THR) and heat release rate (HRR) of the density board. These findings demonstrate the effectiveness of the cysteine-based flame retardant.