Boron-containing Schiff base flame retardant ((E)-2-([2,4-dihydroxybenzylidene]amino) ethyl dihydrogen borate (B-HIBD) was prepared easily and successfully. Thermogravimetric analysis (TGA) showed that when the additive amount was only 3 wt%, the introduction of B-HIBD significantly improved the thermal stability of epoxy resin (EP) composites. The cone calorimeter test showed that compared with pure EP, the peak of heat release rate (PHRR), total heat release (THR), smoke production rate (SPR)，total smoke production (TSP) ，and the releasing of CO for 3 wt% B-HIBD/EP reduced by 58.2, 18.3, 65.9, 51.2, and 28.4%, respectively, showing that B-HIBD could significantly enhance the fire safety of EP composites. This promotion has been embodied not only in the catalysis function of the Schiff base group containing benzene ring but also in borate participating in the carbon-forming process, promoting the dehydration and carbonization of the EP surface and delaying the transfer of mass and heat in the combustion process, which enhance performance for flame retardant. So it is an efficient strategy to develop a novel type of high-efficiency boron-containing Schiff base flame retardant to improve the fire safety for EP. K E Y W O R D S borate, boron-containing Schiff base, EP composites, fire safety, flame retardant mechanism 1 | INTRODUCTION Epoxy resin(EP) has been utilized widely in the fields of adhesive, coating, laminate, automotive, and construction industries due to its superior adhesion，insulation，mechanical toughness, and chemical resistance. However, EP has poor fire performance, which produces serious security risks and limits its industrial application. 1-4 Over recent decades, polymer materials have been required to meet the characteristics of good flame retardancy, flexible structure, and easy chemical modification. The development of new flame retardants is of great significance for the realization of long-term high-efficiency flame retardancy for polymer materials. Schiff base is a class of organic compounds obtained by dehydration condensation reaction of amine and aldehyde compound, containing functional imine group R 1 R 2 C=NR 3 . 5-8 Recently, great interest has risen in Schiff base group containing aromatic ring for flame retar-dant，which improves the thermal stability of EP effectively, enhances hydrogen bonding ability in thermal degradation process, and has an obvious carbonization tendency, which plays an important role in promoting the formation of residue char. 9 Wu et al. 10 designed a novel aromatic Schiff base "5-(benzylidene-amino)-isophthalic acid dimethyl ester (BA) as a self-crosslinking monomer of PET. It is found that BA n PETs can effectively enhance the char formation and has excellent flame retardancy property and non-dripping behavior. Magdy et al. 11 used Vanillin-Schiff's bases (VSB) as thermal stabilizers and co-stabilizers in air at 180 C for PVC (Polyvinyl chloride). It is found that VSB can impart high-efficiency thermal stability to PVC. In addition, Salen-based Schiff base...
