Metal hydroxides synergists

It has been shown that the required loading levels of metal hydroxides to flame retard polyolefins can be reduced by the addition of transition metal oxides as synergistic agents. For example, a combination of 47.6% MH modified with nickel oxide in PP gave a UL94 V-0 flammability rating, which would require -55% of unmodified MH.4 These systems, however, can only be used where the color of the product is not important. 

The addition of metal nitrates to improve the flame retardancy of metal hydroxides and EVA has been reported.64 Synergistic behavior was observed by an addition of 2% of copper nitrate to EVA containing only 33% ATH, in which the oxygen index was raised from 19.9% to 30.0%. 

Halogenated compounds such as bis(alkyl ether)tetrabromobisphenol A or decabromodiphenyl oxide (DECA) may be used as flame-retardants for polyolefin foams, eventually using antimony oxide, metal oxides, boric acid salts, and metal hydroxides as synergist.92 For example Weil and Levchik93 reported that using suitable amounts of DECA and Sb203, polyethylene foams rated UL94 HF-1 are obtained. 

Isarov A, et al. Non-halogen flame retardant polyolefin compounds via synergistic blends of metal hydroxides and mineral fillers. International Polyolefins, conference proceedings. Society of Plastics Engineers 2007. 

Biron M. Halogen free retardant polypropylene HFFR PP synergistic effects between mineral additives and metal hydroxides, web article (www.special-chem4polymers.com). SpecialChem S.A. 24 November 2008 (downloaded 4 December 2008). 

There have been recent commercial developments at some major FR producers where nanoclays have been combined with metal hydroxide fire retardants acting synergistically. As nanodays are added at relatively small amounts, typically 1-5 wt%, and metal hydroxides traditionally at much higher loadings, these synergies may be exploited to allow lower overall loading levels of nanoday and metal hydroxide. 

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