Synthesis of a Magnesium/Aluminum/Iron layered double hydroxide and its flammability characteristics in halogen-free, flame-retardant Ethylene/Vinyl acetate copolymer composites

Mg-Al-Fe ternary hydrotalcites were synthesized by a coprecipitation method and characterized with powder X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The flame-retardant effects of Mg/Al-CO3 layered double hydroxides (LDHs) and Mg/Al/Fe-CO3 LDHs in an ethylene/vinyl acetate copolymer (EVA) were studied with the limited oxygen index (LOI), the UL-94 test, and the cone calorimeter test (CCT), and the thermal degradation behavior of the composites was examined by thermogravimetric analysis. The results showed that the LOI values of the EVA/(Mg/Al/Fe-CO3 LDH) composites were basically higher than those of the EVA/(Mg/Al-CO3 LDH) composites at the same additive level. In the UL-94 test, there was no rating for the EVA/(Mg/Al-CO3 LDH) composite at the 50% additive level, and a dripping phenomenon occurred. However, the EVA/(Mg/Al/Fe-CO3 LDH) composites at the same loading level of LDHs containing a suitable amount of Fe3+ ion reached the V-0 rating, the dripping phenomenon disappearing. The CCTs indicated that the heat release rate (HRR) of the EVA composites with Mg/Al/Fe-CO3 LDHs containing a suitable amount of Fe3+ decreased greatly in comparison with that of the composites with Mg/Al-CO3 LDHs. The introduction of a given amount of Fe3+ ion into Mg/AlCO3 LDHs resulted in an increase in the LOI, a decrease in the HRR, and the achievement of the UL-94 V-0 rating. (c) 2007 Wiley Periodicals, Inc.