Highly efficient multielement flame retardant for multifunctional epoxy resin with satisfactory thermal, flame-retardant, and mechanical properties

Multifunctional epoxy resins with excellent, thermal, flame-retardant, and mechanical properties are extremely important for various applications. To solve this challenging problem, a novel highly efficient multielement flame retardant (PMSBA) is synthesized and the flame-retardant and mechanical properties of modified epoxy resins are greatly enhanced without significantly altering their and thermal properties by applying the as-synthesized PMSBA. The limiting oxygen index value reaches up to 29.6% and could pass the V-0 rating in the UL-94 test with even low P content (0.13%). Furthermore, cone calorimetry results demonstrate that 30.3% reduction in the peak heat release rate for the sample with 10.0 wt% PMSBA is achieved. X-ray photoelectron spectroscopy and scanning electron microscopy indicate that Si-C, Si-N, and phosphoric acid derivative can be transformed into a multihole and intumescent char layer as an effective barrier, preserving the epoxy resin structure from fire. More importantly, mechanical properties such as impact strength, tensile strength, and flexural strength are also increased by 63.86%, 33.54%, and 15.65%, respectively, which show the incorporation of PMSBA do not deteriorate the mechanical properties of modified epoxy resins. All the results show that PMSBA is a promising strategy for epoxy resin with satisfactory, thermal, flame-retardant, and mechanical properties.