Organosilicone-based clustered phosphinic acid endows outstanding synergistic flame retardancy of epoxy resins

In this study, an organosilicone-based clustered phosphinic acid (MVCP) was successfully synthesized by an addition reaction with 2,4,6,8-tetra-methyl-2,4,6,8-tetra-vinyl- cyclo -tetrasiloxane (MVC) and hypophosphorous acid (HPA). MVCP was applied to biscitraconimide-reinforced epoxy resin (BCIEP) systems separately or along with TAD, a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative flame retardant. MVCP/TAD modified BCIEP were investigated systematically concerning on the flame retardancy and mechanism. When the flame retardants containing reached 3 wt%, the limiting oxygen index (LOI) of 3(MVCP/TAD)/BCIEP was increased to 31.2%, while UL 94 reached V-0 level. The peak heat release rate (pk-HRR) of 3(MVCP/TAD)/BCIEP was reduced by 37.3% and the charring residual rate was increased by 7.3% in the cone calorimetry test results, compared to those of BCIEP. Upon combustion, the clustered MVCP formed an aerogel-like residual carbon structure on the surface of the blends through the characteristics of its own silica aggregation, indicating that MVCP was an excellent condensed phase flame retardant. Meanwhile, MVCP reduced the damage of TAD to the mechanical properties of the matrix, showing a broad application prospect.