Enhanced Flame Retardancy and Smoke Suppression of the Silicone Rubber Foam With Low Loading of Modified Expandable Graphite

The flame-retardant silicone rubber foam (SRF) composites were prepared by adding a low loading of expandable graphite modified with gamma-(2,3-epoxypropoxy)propytrimethoxysilane (EG@KH560). The EG@KH560 was characterized by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Meanwhile, the effects of EG@KH560 on the micromorphology, flame retardancy, mechanical properties, thermal stability, and combustion behavior of SRF/EG@KH560 composites were investigated. The results show that the compatibility between EG@KH560 and the SRF substrate was significantly improved, thereby reducing the deterioration of tensile and compressive strength in the composites. The composite containing only 2 parts EG@KH560 per hundred parts of the base polymer (2 phr) exhibited excellent flame-retardant performance, which can pass the FV-0 rating during the vertical combustion test with a high limiting oxygen index (LOI) value of 31.2. The thermal stability of the composite was also enhanced, as evidenced by a notable increase in the maximum thermal decomposition temperature and the residues at 900 degrees C. Moreover, the total heat release and total smoke release of SRF containing 2 phr EG@KH560 were reduced by 13.1% and 61.0% compared with pure SRF in the cone calorimetry test, indicating a significant improvement in fire safety for the composite with the addition of EG@KH560.