A Series of Novel Flame Retardants Produced with Nanosilica, Melamine, and Aluminum Diethylphosphinate to Improve the Flame Retardancy of Phenolic Resin

To facilitate the flame retardancy of phenolic resin (PF), a series of novel flame retardants with nano-SiO₂, melamine, and aluminum diethylphosphinate (ADP) were freshly prepared and tested. A thermogravimetric analysis, cone calorimeter, and scanning electron microscopy were employed to determine the thermal decomposition, flame retardancy, combustion properties, and structure of the carbon residue layer of PF. The pyrolysis kinetic parameters of modified PF were then computed, and the pyrolysis process was appraised. The results indicated that when 1.5 wt % of nano-SiO₂, 3 wt % of melamine, and 15 wt % of ADP were added to PF, the limiting oxygen index value reached 39.6%, and UL-94 passed the V-0 level. A substantial synergistic effect was also observed. The thermogravimetric analysis revealed that the char residue at 800 °C reached 59.93 wt %. Furthermore, in the cone calorimeter test, the total thermal release and thermal release rate decreased to 30.7 MJ/m² and 105.7 kW/m², respectively.