Synergistic effects of aluminum hydroxide, red phosphorus, and expandable graphite on the flame retardancy and thermal stability of polyethylene

Abstract The flame‐retardant low‐density polyethylene (LDPE) composites loading aluminum hydroxide (ATH), red phosphorus (RP), and expandable graphite (EG) were successfully prepared. The flame retardancy, the thermo‐oxidative stability, and the mechanical property of the composites were investigated. The synergistic effect of ATH, RP, and EG on the flame‐retardant property and thermal behavior of LDPE were observed. The limiting oxygen index value of LDPE significantly increased from 17.1% to 25.4% upon the incorporation of 15 wt.% of the mixture of three fillers with ATH:RP:EG mass ratio of 1:1:1; and this composite achieved the V‐0 classification of the UL94 vertical burning test. The thermogravimetric analysis of this composite under air atmosphere revealed that its residue weight remained 27.89% at 900°C. Furthermore, the results of tension tests indicated that the surface modification of ATH by magnesium stearate and RP by poly(methylhydrosiloxane) noticeably improved the tensile strength and the elongation of the composite.