Synergistic flame‐retardant effect of modified hydrotalcite and expandable graphite for silicone rubber foam

Abstract Silica gel‐coated hydrotalcite (LDHs) flame retardants (SiLDHs‐Ce) are prepared by the sol–gel method. The synergistic effect of SiLDHs‐Ce and expandable graphite (EG) on the silicone rubber foam (SRF) is studied through limiting oxygen index (LOI), Cone Calorimeter Test (CC), thermogravimetric infrared spectrometer (TG‐IR), and scanning electron microscopy. The results show that SiLDHs‐Ce and EG can improve the flame retardant properties of the SRF materials. The LOI value of the SRF material can reach 40.1% when the ratio of EG to SiLDHs‐Ce is 2:1, and the heat release rate (HRR) and total heat release (THR) are reduced by 66.60% and 52.76%, respectively, compared with the original. The minimum SPR of the SRF material is 0.010 m 2 s −1 when 1 wt% SiLDHs‐Ce has been added. TG‐IR results show that the addition of EG and SiLDHs‐Ce increased the carbon residue rate of SRF materials. Results show that the residual carbon‐containing EG and SiLDHs‐Ce is denser. It is inferred that the synergistic flame retardant mechanism of SiLDHs‐Ce and EG on the SRF is mainly condensed phase flame retardant, augmented by gas‐phase flame retardant. The results of this study can provide guidance for the development of environmentally friendly silicone rubber foam.