It is a halogen-free flame retardant in an organophosphorus nitrogen system, and the product complies with ROHS requirements. When XF-8501B flame retardant is added to PA, PBT and PET materials, it will foam and expand on the surface of the resin during combustion to form a porous carbon layer. This carbon layer plays the role of heat insulation, oxygen isolation and prevention of the formation of molten droplets. This flame retardant also has a certain effect of suppressing the amount of smoke produced and does not generate toxic or corrosive gases. It contains no melamine residue and can pass the double 85 test. It features non-absorbency, no precipitation, excellent thermal stability and processability, making it an ideal, highly efficient and environmentally friendly flame retardant.