Effect of expandable Graphite/Hexaphenoxycyclotriphosphazene beads on the flame retardancy of silicone rubber foam

Silicone rubber foam (SiF) with EG/HPCTP was prepared by high-temperature vulcanization. The flame retardancy of SiF was evaluated using the LOI (limiting oxygen index), UL-94, cone calorimetry test (CCT), thermogravimetric analysis (TGA), and mechanical properties. The results showed that EG/HPCTP could improve the LOI of SiF, and the SiF could pass the UL-94 V-0 rating. Compared with pristine SiF, EG/HPCTP could reduce the total heat release rate (THR), heat release rate (PHRR). Digital images of the char residues showed that the HPCTP was beneficial to promote the strength of SiF with EG. TGA showed that the branched decomposition temperature and main chain pyrolysis temperature of SiF were delayed. Mechanical properties analysis showed that EG and HPCTP could improve the mechanical properties of SiF. These indicated that the addition of EG/HPCTP was a good approach to prepare high effective flame-retarding SiF.