Synergistic Flame Retardant Effect of Organic Phosphorus–Nitrogen and Inorganic Boron Flame Retardant on Polyethylene

In this study, to develop an organic/inorganic synergistic flame retardant, organic phosphorus–nitrogen flame retardant 6,6‐(((sulfonylbis(4,1‐phenylene)) bis(azanediyl))bis(thiophen‐2‐ylmethylene))bis(6H‐dibenzo[c,e][1,2]oxaphosphinine 6‐oxide (DOPO‐N) and inorganic boron flame retardant zinc borate (ZB) were selected. The flame retardant properties of polyethylene (PE) containing ZB/DOPO‐N were investigated. PE/20%ZB/10%DOPO‐N had better thermal stability and flame retardant properties. The limiting oxygen index of PE/20%ZB/10%DOPO‐N reached 24.6%, and UL 94 V‐0 rating was attained. The peak heat release rate, total heat release, average effective heat combustion, and fire growth index of PE/20%ZB/10%DOPO‐N were lower than when ZB and DOPO‐N were added separately. In addition, the flame retardant mechanism was investigated using scanning electron microscopy, X‐ray diffraction, energy dispersive X‐ray, and Fourier transform infrared spectroscopy. ZB/DOPO‐N simultaneously exerted condensed phase and gas phase flame retardant effect. POLYM. ENG. SCI., 60: 414–422, 2019. © 2019 Society of Plastics Engineers