Flame retardants borate-based

DuPont have patented a flame retardant composition based on melamine pyrophosphate, with or without zinc borate, for use in a number of thermoplastic resins (US Patent 5859099). 

Boron compounds such as borax and boric acid are well-known fire retardants in cellulosic products and coatings.12 However, the use of boron compounds such as zinc borate, ammonium pent-aborate (APB), melamine borate, boric oxide, boron phosphate, and other metal borates in polymers has become prominent only since early 1980s.3 6 This chapter will review the chemical and physical properties, the end-use applications, as well as the mode of actions of major boron compounds as fire retardants in different applications. Since boron-based flame retardants are extensively used and quoted in literature, only those formulations of commercial importance and representative literature examples will be discussed and/or cited in this chapter. 

A mixture of ammonium chloride and borax was one of the treatments of cellulosic fabrics reported by Gay-Lussac in 1821. Due to its low dehydration temperature and water solubility, sodium borates are only used as flame retardants in cellulose insulation (ground-up newspaper— see Sections 9.2.1.2 and 9.2.2.1), wood timber, textiles, urethane foam, and coatings. For example, a mixture of urethane (100 parts), borax (100 phr), and perlite (30phr) was claimed to provide flame-retardant urethane foam.8 Borax in conjunction with boric oxide, silica, ammonium chloride, and APB as ceramizing additives and volume builders, are claimed in a fire-protection coating based on polybutadiene and silicone microemulsion.9 Using a modified DIN 4102 test, the chipboard with the coating showed a loss of mass less than 1% and there was no pyrolysis of the wood sample. 

Polyolefins When used in conjunction with a halogen-based flame retardant, this zinc borate can partially replace antimony oxide (30%-40%) and still maintain the same fire test performance. In addition, it can improve aged elongation properties, increase char formation, and decrease smoke generation. The B203 moiety in zinc borate can also provide afterglow suppression (Table 9.6). 

In EPR formulations, calcium borate was found to be a good replacement for the combination of antimony trioxide with an organic flame retardant Calcium borate, in addition to affecting flame retardation, also reinforces the polymer. Another alternative is based on huntite/hydromagnesite filler. Here, some antimony trioxide and organic flame retardant combination must be added. The huntite/magnesite filler combination cannot, by itself, halt flame spread. ... 

Manufacturers of various fillers continue studies on altemative systems. Most antimony oxide used as a fire retardant can be replaced by a combination of zinc borate without the loss of other properties (in some cases improvements are reported). Another option is to use the same filler systems which are used in polyethylene insulated cables and wires. These are based on magnesium hydroxide and aluminum hydroxide. These systems pcrfoim as flame retardants but require a high filler concentration which affects jacket resistance and mechanical performance. Recently, new coated grades have been developed which can be used at up to 65 wt% without the loss of properties or productivity (extrusion rates 2,500 m/min of cable are possible). ... 

Some of the inorganic compounds, snch as antimony trioxide (Sb203), or boron-based componnds, snch as zinc borate, fnnction as synergists rather than directly as flame retardants bnt enhance the effectiveness of the latter. Antimony trioxide is used mainly with halogenated flame retardants. 

In the present chapter, we report some of om study on both raw and surface-modified Grewia optiva fiber-reinforced UPE matrix-based composites, which possess enhanced mechanical and physico-chemical properties when compared with UPE matrix. In addition to the effect of flame retardants, i.e., magnesium hydroxide and zinc borate, on flame resistance, the behavior of resulted Grewia optiva fiber-reinforced composites have also been evaluated and was foimd to be improved. A significant discussion on the work of other researcher s work has also been added in the chapter. 

Joseph Storey (part of the Banner Chemicals Group) sells Storflam flame retardants based on borates and starmates. They are claimed to benefit from their small particle size, in contrast to coarser grained competitors. Some of these additives can replace antimony trioxide, giving improved char yields, and good smoke suppression can be achieved in nonhalogen polymer systems. 

Bayer markets a dimethylpropane phosphonate-based FR called Levagard VP SP 51009 to enable rigid PU foam to meet fire regulations. Clariant offers liquid phosphorus polyols for the protection of polyether flexible and slabstock moulded automotive foams. Flexible PU is also commonly flame retarded in Europe with chlorinated phosphate esters. Borates have not shown... 

Although certain cellulose esters, such as the ammonium salt of phospho-rylated cotton and cellulose phosphate [9015-14-9], are flame-resistant, the attachment of most currently used durable polymeric flame retardants for cotton is through ether linkage to the cellulose at a relatively low degree of substitution (DS). Nondurable flame retardants based on liquid-or vapor-phase applications of boric acid [10043-35-3] or methyl borate [121-43-7] are used in treatment of cotton batting for upholstery, bedding, and automotive cushions (112-114). Cotton carpet materials will pass the U.S. Consumer Product Safety Commission (CPSC) federal flammability test for carpets (16 CFR1630) when cross-hnked with polycarboxylic acids such as 1,2,3,4-butanetetracarboxylic acid or citric acid with sodium phosphate, sodium hypophosphite, sodium bicarbonate, or sodium carbonate catalysis (115). 

For instance, the effect of smoke reduction and flammability performance of zinc-based compounds (i.e. zinc borate and zinc hydroxystannate) in epoxy resin composites used in the aerospace and aeronautical industries have been analyzed (Formicola et al., 2011). The flammability performance of neat and loaded systems was analyzed by using micro-combustion calorimetry, while smoke generation, in terms of CO and CO2 production, was analyzed under dynamic conditions by using cone calorimetry. The experimental results have shown that the dispersion of zinc borate and zinc hydroxystannate within epoxy matrices leads to a significant variation in flame retardant properties in particular the total heat release is reduced by about 25% and 30%, respectively, and the heat release capacity by about 30% and 50%, respectively. The system containing zinc hydroxystannate shows an enhancement in all smoke reduction properties, and both compounds lead to a reduction of the CO2/CO ratio. 

Fillers may promote char magnesium hydroxide, zinc borate, antimony oxides require high loadings and can degrade mechanical and other properties. Toxicity of antimony-based retardants is a concern. Can be used with other flame retardants synergistically. 

Since NBR/PVC has basic good flame resistance it may be used in hose and belt applications where this is a requirement. A 70/30 or 50/50 NBR/PVC base elastomer should be selected and use non-black fillers, including alumina trihydrate (e.g.. Hydrated Alumina 983), magnesium hydroxide, and zinc borate (e.g., Firebrake ZB) as flame retardant fillers. Calcium carbonate will assist in reducing smoke emission. In addition a phosphate plasticizer such as Kronitex 100 or chlorinated paraffin like Chlorowax 40 should be used as the only plasticizer types. 

Most of the chemicals used in fire-retardant formulations have a long history of use for this purpose, and most formulations are based on empirical investigations for best overall performance. These chemicals include the phosphates, some nitrogen compounds, some borates, silicates, and more recently, amino-resins. These compounds reduce the flame spread of wood but have diverse effects on strength, hygroscopicity, durability, machinability, toxicity, gluability, and paintability (J, 12, 13). 

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