Fire resistant elastomers

Fire Resistant Elastomers. The poly(aryloxyphosphazene) elastomers offer excellent fire resistance without incorporating halogen in the polymer or as an additive. These polymers are self-extinguishing in air and generate only moderate non-corrosive smoke and a minimum of toxic combustion products upon combustion (50-53). The poly(aryloxyphosphazene) elastomers (APN ) have excellent potential for applications such as... 

Lyon, R.E., Speitel, L., Walters N., and Crowley, S. 2003. Fire-resistant elastomers. Fire Mater. 27 195-208. 

R. E. Lyon, U. S. Department of Transportation, Federal Aviation Administration, Cabin and Fire Safety Reports, Fire-Resistant Elastomers, DOT/FAA/AR-TNOl/ 104. 

Polv(Arvloxyphosphazene) Elastomers. Poly(aryloxyphosphazene) elastomers, III, prepared by the reaction of chloropolymer with mixed phenoxides, offer excellent fire resistance without the incorporation of halogens in the polymer or as an additive. In addition, in a fire situation smoke evolution from these polymers... 

Poly(aryloxyphosphazene) elastomers can be cured with peroxides, sulfur and radiation. The resulting vulcanizates are resistant to attack by moisture and oils and have been found to have desirable characteristics for electrical insulation applications where fire safety is a concern (Table II) (12). Fire resistant, low smoke, closed cell foams with excellent properties (Table III) have also been developed from poly(aryloxyphosphazene) elastomers (13). Applications for these foams, which can be produced as either slabstock or tube stock, are being developed for military, aerospace and commercial uses. (See Table II and III.)... 

Poly(aryloxyphosphazene) elastomers offer outstanding fire resistance without the presence of halogen. In a fire these elastomers produce low levels of smoke as well as low toxicity and non-corrosive off-gases. 

Other Applications. Thus far the phosphazene fluoroelastomers (PNF) and aryloxyphosphazene elastomers (APN) have moved to the commercial stage. In addition to elastomers, phosphazenes are being investigated as fluids, resins and plastics. Other areas which hold promise include fire resistant paints (55), fiber blends and additives, agrichemicals and herbicides, drug release agents and electrically conducting polymers (6). 

Flexible PVC is appreciated for the versatility of its characteristics according to the formulation. Significant quantities of fillers and plasticizers are used to optimize some of the characteristics such as behaviour at low temperatures, fire resistance, flexibility and hardness in the elastomer range, low price, electric insulation, easy welding and joining, possibility of transparency, food contact, fireproofing. 

By varying the nature of the side chain, R, various elastomers, plastics, films, and fibers have been obtained. These materials tend to be flexible at low temperatures, and water and fire resistant. Some fluoroalkoxy-substituted polymers (R = CHXFJ are so water repellent that they do not interact with living tissues and promise to be useful in fabrication of artificial blood vessels and prosthetic devices. 

Elastomers of this type are usually cross-linked during fabrication, and often contain fillers such as carbon black or iron oxide to reduce the compliance of the elastomer (i.e. to provide a greater resistance to deformation). Such materials are depicted in Figure 3.1. They are used in technology because of their flexibility and elasticity at low temperatures (-60 °C), their resistance to hydrocarbon solvents, oils, and hydraulic fluids, and their fire resistance.145 For these reasons, they are utilized in aerospace and advanced automotive applications. Some interest exists in their development as inert biomaterials, mainly because of their surface hydrophobicity and consequent biocompatibility. 

In general, boric acid esters (also called borester) derived from alcohols and boric acid are hydrolytically unstable for general use in plastics/elastomers, wood, paper, or cotton. However, the pressure treating of wood with trimethylborate [B(OCH3)3] is reported to be effective in rendering it fire resistant.88 In this case, once trimethylborate penetrates the wood, it will revert back to boric acid. 

The range of silicones for these form-in-place applications continues to grow (5). A variety of silicone foams is particularly useful in fire-resistant penetration seals. A promising new silicone is a latex that deposits a coherent and fully cured elastomer on loss of water. These new forms offer the convenience of silicones from water-based systems and are appearing as easy-to-use, water-based silicone caulks and as high-performance exterior-coating systems. 

Eypel A Acoustic Barrier Sheet. [Ethyl] Poly(aryloxyphosphazene) elastomer fire-resistant acoustic mass sheeting. 

BS7917 Elastomer insulated fire resistant (limited circuit integrity) cables for fixed wiring in ships and on mobile and fixed off-shore units. Requirements and test methods. 

Although they are not elastomers, other phosphazenes also offer potential In areas requiring heat and fire resistance. Mixed fluoroalkoxy - aryloxy substituted cyclic phosphazenes are currently attracting Interest for fire resistant fluid applications (46). In other studies, cyclophosphazene matrix resins have been prepared which have potential for high temperature adhesive applications (47) and as composite matrix materials (48). These studies serve to further demonstrate the enhanced thermal stability and fire resistance which can be achieved with these phosphorus - nitrogen systems. 

Uses Aq. fire-resist, hydraulic fluids rubber processing lubricant high-temp. lubricants for furnaces antifoam agents PU chain extender intermediates for urethane foams, adhesives, coatings, elastomers. 

R = OCH2CF3 or other fluorine-substituted alkoxy group is hydrophobic, chemically stable, has easily formed elastomers, and is very fire-resistant. 

Furan prepreg n. Latent catalysts announced in 1972 made it possible to produce fiiran-resin prepregs of acceptable shelf life, which avoided the difficulties experienced with the wet-layup process. These composites possess good heat and chemical resistance, excellent surface hardness and fire resistance. Harper CA (ed) (2002) Handbook of plastics, elastomers and composites, 4th edn. McGraw-Hill, New York. 

The paper considers the possibility of using microdispersed silicon carbide along with slurries as a functional filler in fire and heat resistant elastomer compositions. It has been shown that slurries formed after grinding and applied together with microdispersed silicon carbide can be used to effectively enhance the fire resistance of elastomer materials and make them cheaper. 

Phosphate esters are produced from phosphorus oxychloride with various alcohols or phenols, or combinations of these hydroxyl compounds. These fluids generally have good thermal and oxidative stabilities and fire-resistancy. However, because of their high polarity, poor Vl-pour point balance, facile hydrolysis and inferior elastomer and paint compatibility, their use in general lubrication is limited. The major use for phosphate esters is in fire-resistant hydraulic oils. 

Silicones are generally very fire resistant, depending on their formulation. Certain silicone elastomers used as encapsulants and cable insulation have excellent values of limiting oxygen index (LOI) or UL rating. A specially processed dimethyl silicone fluid, Dow Corning 561, used as a transformer coolant is far more fire resistant than mineral oil. 

Silicone elastomer insulated cables and wiring provide connections which retain their integrity and flexibility over a wide temperature range, e.g. from -55 C or even lower to +250 C. They are fire resistant, but if damaged or destroyed by fire leave an insulating residue of silica and do not evolve highly toxic fumes. ... 

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