Flame retardancy materials

Toxicology. Two factors should be considered when discussing the toxicity of flame-retardant materials the toxicity of the compounds themselves and the effect of the flame retardants on combustion product toxicity. 

Two elastomers have been commercialized with unique property profiles. One has fluoroalkoxy substituents that provide resistance to many fluids, especially to hydrocarbons. This material also has a broad use temperature range and useful dynamic properties. Aryloxy substituents provide flame retardant materials without halogens. 

Polyphosphonates are well-known flame-retardant materials [110] and are generally prepared by melt [111,112], interfacial [113-115] and solution polycondensation methods [116]. A typical example of synthesis is the polycondensation of bifunctional organophosphorus compounds, such as dichlorophenylphosphine oxide, with bisphenols [117,118]. 

Most circuit boards are FR-4 boards that meet standards for fire safety by the use of brominated epoxy resins in which the reactive flame-retardant tetrabromobisphenol A (TBBPA) forms part of the polymeric backbone of the resin. Alternative flame-retardant materials are used in only 3-5 per cent of the FR-4 boards, but additional alternative flame-retardant materials are also imder development. Little information exists concerning the potential environmental and human health impacts of the materials which are being developed as alternatives to those used today that are based on brominated epoxy resins. 

Principles and Characteristics Combustion analysis is used primarily to determine C, H, N, O, S, P, and halogens in a variety of organic and inorganic materials (gas, liquid or solid) at trace to per cent level, e.g. for the determination of organic-bound halogens in epoxy moulding resins, halogenated hydrocarbons, brominated resins, phosphorous in flame-retardant materials, etc. Sample quantities are dependent upon the concentration level of the analyte. A precise assay can usually be obtained with a few mg of material. Combustions are performed under controlled conditions, usually in the presence of catalysts. Oxidative combustions are most common. The element of interest is converted into a reaction product, which is then determined by techniques such as GC, IC, ion-selective electrode, titrime-try, or colorimetric measurement. Various combustion techniques are commonly used. 

Other substitutes were available, but a report by the New York State Environmental Protection Agency stated these were inferior to phosphate, posed an alkalinity hazard, and reduced the effectiveness of flame-retardant materials.10 Nevertheless, this did not stop the states of Indiana and New York from banning the sale of nearly all detergents containing phosphates in 1973. A number of other states, counties, and municipalities did not go this far, but limited the amount of STPP to... 

These can be inorganic materials such as calcium silicate, mineral wool, diatomaceous earth or perlite and mineral wool. If provided as an assembly they are fitted with steel panels or jackets. These are woven noncombustible or flame retardant materials the provide insulation properties to fire barrier for the blockage of heat transfer. 

Clay-polymer nanocomposites have proven to be interesting candidates as gas barrier materials preventing permeation of volatile gases by creating a long path for diffusion and as flame-retardant materials. Previous work mainly involves the utihzation of cationic clays, although LDH materials... 

Sakai S, Wantanabe J, Takatsuki H, et al. 2001. Presence of PBDDs/DFs in flame retardant materials and their behavior in high-temperature melting processes. BFR 59-63. 

Striebich RC, Rubey WA, Tirey DA, et al. 1991. High-temperature degradation of polybrominated flame retardant materials. Chemosphere 23(8-10) 1197-1204. 

This term is used for any additives that allow a polymer to retard a flame, or for any polymer that shows the ability to slow fire growth when ignited. It does not mean noncombustible or ignition resistant—these are very different terms and should not be used to describe a flame-retardant material. A material that is truly noncombustible or ignition resistant either cannot be combusted (no thermo-oxidative decomposition can occur) or cannot be ignited with a particular size... 

Humanity is, by nature, emotional, and emotions on both sides of this issue make progress difficult for new fire safe materials, whether in response to new fire risk scenarios or in response to non-fire-related issues. This last point should make it clear that flame retardancy of plastics is not a simple scientific issue, but one that must take into consideration societal, emotional, and non-fire-related issues to make an acceptable new flame-retardant material in the twenty-first century. 

Other work in this area has been reported in recent years. Of particular note is that of Lyon, which has also been involved in synthesizing inherently flame-retardant materials to improve the fire resistance of aircraft interiors.11 12... 

Castrovinci, A. Lavaselli, M. Camino, G. Recycling and disposal of flame retarded materials. In Advances in Fire Retardant Materials. Horrocks, A. R. Price, D., Eds.., Boca Raton, FL CRC, 2008, pp. 213-232. 

Weil, E. D., Recent developments in phosphorus flame retardants, Proceedings of 3rd Beijing International Symposium on Flame Retardants and Flame Retardant Materials, 1999, Beijing, China, pp. 177-183. 

Wang, T. L., Cho, Y. L., and Kuo, P. L., Flame-retarding materials II. Synthesis and flame-retarding properties of phosphorus-on-pendent and phosphorus-on-skeleton polyols and the corresponding polyurethanes, J. Appl. Polym. Sci., 2001, 82, 343-357. 

In this chapter, we have discussed recent developments of intumescent flame-retarded materials in terms of reaction and resistance to fire. Research work in intumescence is very active. New molecules (commercial molecules and new concepts) have appeared. Nanocomposites are a relatively new technology in the held of flame retardancy. This technology gives the best results combined with conventional FRs and leads to synergistic effects with intumescent systems. Very promising developments in the synergy aspects are then expected and efforts should be continued in this way. 

Bolger, R., Flame retardant materials, Industrial Minerals, 29, January, 1996. 

Nachtigall, S. M. B., Miotto, M., Schneider, E. E., Mauler, R. S., and Forte, M. C. 2006. Macromolecular coupling agents for flame retardant materials. European Polymer Journal 42 990-99. 

Whereas UL 94 delivers only a classification based on a pass-and-fail system, LOI can be used to rank and compare the flammability behavior of different materials. In Figure 15.2 the increasing LOI values are presented for different polymers as an example POM = poly(oxymethylene), PEO = poly(ethyl oxide), PMMA = poly(methyl methacrylate), PE = polyethylene), PP, ABS, PS, PET = polyethylene terephthalate), PVA = poly(vinyl alcohol), PBT, PA = poly(amide), PC, PPO = poly(phenylene oxide), PSU, PEEK = poly(ether ether ketone), PAEK = poly(aryl ether ketone), PES, PBI = poly(benzimidazole), PEI = poly(ether imide), PVC = poly(vinyl chloride), PBO = poly(aryl ether benzoxazole), PTFE. The higher the LOI, the better is the intrinsic flame retardancy. Apart from rigid PVC, nearly all commodity and technical polymers are flammable. Only a few high-performance polymers are self-extinguishing. Table 15.1 shows an example of how the LOI is used in the development of flame-retarded materials. The flame retardant red phosphorus (Pred) increases... 

Figures 15.8 and 15.9 illustrate examples of how cone calorimeter data can be used in the development of flame-retarded materials. PA 66-GF without Pred showed typical fire behavior for noncharring polymers containing inorganic glass fiber as inert filler,69 when high external heat flux is applied. The shape of the HRR curve is divided in two different parts. In the beginning, the surface layer pyrolysis shows a sharp peak, followed by a reduced pyrolysis rate when the pyrolysis zone is covered by the glass fiber network residue layer. When Pred was added, the PA 66-GF samples were transformed into carbonaceous char-forming materials, which led to a...

Efficient fire protection is also based on the consideration of product or scenario-specific hazards, which may lead to very specific materials development goals. Examples are the combination of impacts, such as vandalism and ignition source for seats in railway vehicles, or a preceding shock wave before the fire impact in navy applications. Some more product-specific phenomena of such kind are related directly to material properties, such as building up an increased risk for pool fires through burning thermoplastic plastics or dripping foams, and thus have become topics in the development of some flame-retarded materials.103... 

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