Synergistic flame retardant effect of α-zirconium phosphate in low-density polyethylene/ethylene-vinyl acetate/aluminum hydroxide hybrids

Organophilic alpha-zirconium phosphate (alpha-ZrP, OZrP) with a lamellar structure is used as a synergistic agent with aluminum hydroxide (ATH) to improve the flame retardancy of low-density polyethylene and ethylene-vinyl acetate (LDPE/EVA) hybrid. The structures of LDPE/EVA/(ATH, OZrP) hybrids are characterized by X-ray diffraction, transmission electron microscopy, and high resolution transmission electronic microscopy. The results indicate that the intercalated and exfoliated nanocomposites are formed. The flammability characterization and synergistic effects of LDPE/EVA/(ATH, OZrP) hybrids have been investigated by cone calorimeter test, limiting oxygen index, and UL-94 tests. The analyses show that hybrids with a given amount of OZrP have apparently reduced the heat release rates and can pass the V-0 rating in the UL-94 test. Based on these findings, a possible and reasonable synergistic flame retardant mechanism of OZrP and ATH is given in the discussion.