A study on flame retardancy and smoke suppression of diatomite/hexaphenoxycyclotriphosphazene in silicone rubber foam

Silicone rubber foam (SRF) is a kind of polymer material with excellent performance but flammable. The flame-retardant SRF was prepared with diatomite (Dia) and hexaphenoxycyclotriphosphazene (HPCTP) as flame retardants. Cone calorimetry tests (CCT), scanning electron microscopes (SEM) and mechanical tests were used to investigate the effects of Dia and HPCTP on the flame retardancy, smoke suppression and mechanical properties of SRF. The results showed that Dia and HPCTP had a synergistic effect on flame retardancy and smoke suppression. With the addition of 5 wt% Dia and 5 wt% HPCTP, the peak heat release rate (PHRR), the total heat release rate (THR), the peak smoke release rate (PSPR) and the total smoke production (TSP) of SRF decreased by 54.43, 37.64, 62.3 and 58%, respectively. With the addition of Dia and HPCTP, the thickness of the carbon layer became thicker, the cracks became smaller and the microstructure became denser. In addition, when the contents of 5 wt% Dia and 5 wt% HPCTP were added, the mechanical properties of SRF were the best; the tensile strength increased to 0.195 MPa, and the elongation at break increased by 109.85%. It provided a new flame-retardant method for SRF.