Flame retardants halogen alternatives

Some of this effort has been directed to replacement of tetrabromobisphenol A, a major reactive component of circuit boards (wiring boards). Extensive development of flame-retarded halogen-free circuit boards has taken place especially in Europe and the Far East to find alternatives to tetrabromobisphenol A-based epoxy circuit boards. The use of phosphate ester additives usually depresses the thermomechanical properties excessively, and so the use of reactive phosphorus compounds has been the preferred approach. 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

C.G. Bergendahl, Alternatives to Halogenated Flame Retardants in Electronic and Electrical Products, IVE Research Publication 99824, Molndal, Sweden, 1999. 

Antimony pentoxide is an alternative to antimony trioxide. It finds applications in semi-transparent materials and dark colors because of its low tinting strength. As with antimony trioxide, antimony pentoxide must be used together with halogen-containing compounds to function as a flame retardant (sec discussion under antimony trioxide). The other advantages of antimony pentoxide include its refractive index which is closer to most materials, its very small particle size, its high specific surface area, and its substantially lower density. Because of its small particle size, its is frequently used in the textile industry since its addition has only a small effect on color or on mechanical properties. Production of fine-denier fibers requires a stable dispersion and a small particle size filler. The flame retardancy of laminates is also improved with antimony pentoxide because small particles are easier to incorporate in the interfiber spaces. 

Many large companies in the U.S. are also looking for non-halogenated flame retardant alternatives. 

To improve flame retardation in HIPS, agents formulated from halogenated compounds have been traditionally used [137, 138]. These compounds form, nevertheless, highly toxic vapors during the combustion process. Recently, alternative flame-retardant compounds have been developed, ensuring that no toxic vapors are expelled, presenting an augmented thermal stability. Furthermore,... 

Joseph Storey has introduced a zinc hydroxystannate flame retardant, which it found to be the closest non-toxic alternative to antimony trioxide in halogenated systems. The new material also has excellent smoke suppression properties. In halogen-free systems, tin char formation occurs, leading to reductions in filler loadings and improved physical properties. 

Nanoeomposites are an environmentally friendly alternative to some types of flame retardants, as they eontain no additional halogens, phosphates or aromaties above those eontained in the ehosen polymer resin. The silicate remains intact at very high temperatures. In addition, whereas many flame retardant compounds, particularly filler types, inerease the earbon monoxide and soot levels produeed during combustion, no similar increases have been observed with nanoeomposites flame retardants. 

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