Novel design and synthesis of bio-based polyelectrolyte complexes for enhancing the flame retardancy of epoxy resin

The flame-retardant efficiency of a single flame retardant is often not as expected, but the process of synthesizing new high-efficiency flame retardants is usually complicated and harsh. Here, a bio-based polyelectrolyte complexes (PA-Ni-PEI) was synthesized by reacting biomass phytic acid, nickel ion and polyethylenimine, and then incorporated into EP as a flame-retardant additive for improving the thermal stability and flame retardancy properties. When the adding of PA-Ni-PEI complexes is 2.0 wt%, the peak heat release rate (PHRR), the total heat release (THR), the total smoke release (TSR) and smoke factor (SF) with a reduction of 30.4%, 24.9%, 36.0% and 55.4%, respectively, and the char residue was improved by 53.9%, compared to EP. The improvement in fire safety was ascribed to the early degradation of EP catalyzed by the decomposition products of the composites, resulting in the formation of a dense, robust and stable cross-linked char layer to prevent heat and oxygen from contacting with epoxy resin . Simultaneously, water and nitrogen-containing incombustible gas are released to reduce the concentration of combustible gas. A new idea for the preparation of EP composites with excellent flame retardancy property was provided by this work.