Intrinsically anti-flammable and highly heat-resistant deoxybenzoin-derived bismaleimide resins containing no conventional flame-retardant elements

The flammability of bismaleimide (BMI) resins limits the application in cutting-edge fields. However, the addition of phosphorus-containing flame retardants results in deteriorated thermal stability of BMI resins. A phosphorus-free flame retardant strategy has been adopted to modify BMI resins while preserving high heat resistance. 3, 3’-Bisallyl-4,4’-bishydroxydeoxybenzoin (BA-BHDB) was synthesized from desoxyanisoin and used as a modifier for BMI resins by replacing conventional 2, 2’-diallylbisphenol A (DBA). The thermal, mechanical and flammability properties of BA-BHDB-cured BMI resins were investigated and compared with those of DBA-cured BMI resins. The cured BA-BHDB-BMI resins exhibit an LOI value for combustion of 35.0% and a UL-94 V-0 rating, whereas the cured DBA-BMI resins display a lower LOI value of 30.0% and a UL-94 V-1 rating. In the cone calorimeter measurements, the PHRR and THR values for combustion of BA-BHDB-BMI were 381.1 kW/m 2 and 92.5 MJ/m 2 , which were 53.2% and 25.2% lower than those of DBA-BMI, respectively. Additionally, the heat resistance of the cured BA-BHDB-BMI resins was greater than that of the DBA-BMI resins, with an initial thermal decomposition temperature of 428 °C and a glass transition temperature of 285 °C. The excellent anti-flammability of BA-BHDB-BMI may be attributed to the superior charring capacity of BA-BHDB, which contributes to the formation of a dense and protective char layer during thermal decomposition.