A PARADOXICAL FLAME-RETARDANT EFFECT OF NITRATES IN ATH-FILLED ETHYLENE-VINYL ACETATE COPOLYMER

摘要

In the course of a study of metal salts as flame retardants, it was surprisingly found that metal nitrates reduced the flammability of ATH-filled ethylene-vinyl acetate copolymer (EVA). The limiting oxygen index (LOI) of ATH-filled EVA was increased by the nitrates in the order of Cu(NO3)(2) . 3H(2)O > (NH4)(2)Ce(NO3)(6) > Zn(NO3)(2) . 6H(2)O > Fe(NO3)(3) . 9H(2)O > Al(NO3)(3) . 9H(2)O > NaNO3. The effects were not caused by the water of hydration. All metal nitrates except NaNO3 reached a UL 94 V-2 rating at 3 phr. Based on TGA, DSC, FTIR, and gas detection, the proposed mechanism of the flame-retardant effect of nitrates is the oxidative-degradation of the polymer to produce noncombustible products (CO2 and nitrogen oxides) at a rate sufficient to interfere with the normal combustion process despite the exothermicity of the oxidative degradation. It is possible that surface carboxylic acid structures also contribute to the flame-retardant effect. (C) 1995 John Wiley & Sons, Inc. [References: 14]