Synergistic flame-retardant effect of sepiolite and magnesium hydroxide/melamine/starch on the properties of silicone rubber composites

In this work, a novel silicone composite with low smoke, high flame retardancy, and good overall mechanical properties was prepared, and the flame-retardant mechanism of sepiolite was explored by studying the application of magnesium hydroxide/melamine/starch/sepiolite system in silicone rubber. The impact of the dosage of sepiolite on the mechanical performances of SR composites was studied. The results showed that when the dosage of sepiolite was 20 phr, the comprehensive mechanical performances of the SR composite were the best. The flame-retardant performances of the specimens were characterized by vertical combustion, the limiting oxygen index, and CCT. With the increase of sepiolite dosage, the limiting oxygen index and vertical combustion of the composites gradually enhanced, the highest peak values of HRR and SPR gradually decreased, and the values of THR and TSP gradually reduced. The SEM pictures of the char residue of CCT showed that the char layer formed by the composites with sepiolite had fewer cracks and a more robust structure. The results of the Shore OO hardness test showed that the addition of sepiolite significantly improved the strength of the char residue. TGA analysis indicated that the thermal stability of silicone rubber with sepiolite was enhanced.