Flame retardancy effects between expandable graphite and halloysite nanotubes in silicone rubber foam

The effect of expandable graphite (EG) and modified halloysite nanotubes (HNTs) on the flame retardant properties of silicone rubber foam (SiF) was studied in this paper. Modified HNTs were obtained by surface modification of the silane-coupling agent A-171. The flame retardancy of SiF was studied by limiting oxygen index (LOI), vertical combustion and cone calorimeter tests. The mechanical properties of SiF were analyzed by a universal mechanical testing machine. The LOI results showed that EG/HNTS@A-171 could enhance the LOI of SiF. The cone calorimeter test results showed that EG/HNTS@A-171 effectively reduced the peak heat release rate, the total heat release rate, the smoke production rate, the total smoke production rate, the CO production rate and the CO₂ production rate and increased the carbon residue rate. TGA shows that main chain pyrolysis temperature of the SiF is delayed by 123 °C. The mechanical properties test results showed that EG/HNTS@A-171 improved the tensile strength of SiF. These results indicated that EG/HNTS@A-171 can significantly improve the flame retardant performance of SiF.