Stable electrically conductive, highly flame-retardant foam composites generated from reduced graphene oxide and silicone resin coatings

To acheive flexible polyurethane (PU) foam composites with stable electrical conductivity and high flame retardancy involved first coating of graphene oxide (GO) onto PU foam surfaces and then chemically reducing the GO with hydrazine to form reduced GO (RGO). The RGO-coated PU foam is then dipped into a solution containing silicone resin (SiR) and silica nano-particles and cured. The resulting composites (PU-RGO-SiR) show superior flame retardancy, thermal stability and mechanical stability relative to the PU starting materials or PU coated with either RGO or SiR alone. The electrical conductivity of the PU-RGO-SiR composites (as high as 118 S m^-1 at room temperature) could almost be retained but with small loss of 9.5% of the original value after 150 cyclic compression. When the samples were subjected to a temperature range from -50 to 400 °C, the electrical conductivity could remain constant at -50 °C, 25 °C, 100 °C, 200 °C, and even at 300 °C and 400 °C; the electrical-conductivity exhibited mild vibration but the vibration range was not beyond 5.6%. Flame retardancy tests show that the limiting oxygen index (LOI) increases from 14.7% for the pure foam to 31.5% for PU-RGO-SiR, and the PU-RGO-SiR composites exhibit a 65% reduction in the peak heat release rate (pHRR) and a 30% reduction in total smoke release (TSR). Thus, stable electrically conductive and highly flame-retardant foam composites have potential applications even in a variety of harsh conditions like high temperature, flame, organic solvents, and external compression.