Remarkable effects of silicone rubber on flame retardant property of high-density polyethylene/magnesium hydroxide composites

•The interfacial compatibility between silicone rubber (SR) and high-density polyethylene (HDPE) was increased by electron beam irradiation.•The addition of SR will significantly reduce the heat release rate of HDPE/magnesium hydroxide (MH) composites.•The addition of SR will significantly increase the amount of carbon layer after the complete combustion of the HDPE/MH composite.•The maximum expansion height of carbon layer formed after complete combustion can reach 2.2 cm. In this study, silicone rubber (SR) was introduced into high-density polyethylene/magnesium hydroxide (HDPE/MH) composites by melt blending, and the electron beam irradiation was used to prepare the irradiation crosslinked flame retardant HDPE composites. The changes of properties of the samples were investigated by melt index test (MI), mechanical property test, thermal stability test (TG/DTG), oxygen index test (LOI) and cone calorimetry (CCT). MI test results indicated that SR can increase the internal lubricity of HDPE composites. The morphology results showed that the SR can promote the interfacial compatibility between MH and HDPE. The test results of mechanical properties further revealed that the addition of SR can effectively improve the continuity between MH and HDPE, which was evidenced by the 240 % increasing of the elongation at break. TGA test results showed that with the continuous increase of SR, the mass loss rate (LR) decreased rapidly, and the residue content increased. When the addition of SR reached 7.5 phr, the LOI was promoted by 27.4 %. CCT results indicated that the addition of SR can effectively inhibit the heat release rate (HRR) and total heat release (THR), but had little effect on the total smoke release (TSP). When 10 phr of SR were added, the content of residue can reach up to 37 %, and the expansion height can reach to 2.2 cm. Conclusively, the SR contributed to significantly synergistic flame retardant property to HDPE composites.