Flame brominated fire retardants

To improve the fire retardancy of polypropylene, beyond the UL 94 V-2 level, it is necessary to use blends of aromatic bromine fire retardants with antimony trioxide as a synergist. The usual loading is between 35% and 40% fire retardant however, the additional cost may prohibit commercialization. Moreover, the presence of aromatic bromine increases the photooxidation of polypropylene67 69 inactivating hindered amines. To reduce the cost without losing in efficacy the combination of brominated flame-retardant/antimony trioxide system with magnesium hydroxide... 

It is intended to use these properties for the assessment of alternative flame retardants (FRs) (including nanoparticles, phosphates, and inorganic metal oxides) in comparison with brominated fire retardants by quantitatively assessing ... 

During the last decade, environmentalists have fought strongly to ban the use of brominated fire retardants, and already a number of plastics processors have voluntarily switched to non-halogenated ones (such as phosphate esters, aluminium trihydride and magnesium hydroxide fire retardants). Still, there are two contradictory forces in the fire retardant industry, one is the constant push for stronger fire-safety standards, and the other is the move to eliminate flame-retardants seen as persistent, bioaccumulative or toxic [19]. 

Figure 1.1 compares the flame retardant efficiency of aliphatic brominated flame retardant and aromatic brominated flame retardant. Because the thermal decomposition of the aliphatic flame retardant starts at temperatures below the thermal decomposition of pol5T)ropylene, it shows very good performance in polypropylene. In contrast, because the aromatic brominated fire retardant is significantly more stable, optimum debromination is not achieved at the temperature of decomposition of polypropylene, and this flame retardant shows inferior performance. 

Bromine compounds are often used as flame retardant additives but 15-20ptsphr may be required. This is not only expensive but such large levels lead to a serious loss of toughness. Of the bromine compounds, octabromo-diphenyl ether has been particularly widely used. However, recent concern about the possibility of toxic decomposition products and the difficulty of finding alternative flame retarders for ABS has led to the loss of ABS in some markets where fire retardance is important. Some of this market has been taken up by ABS/PVC and ASA/PVC blends and some by systems based on ABS or ASA (see Section 16.9) with polycarbonates. Better levels of toughness may be achieved by the use of ABS/PVC blends but the presence of the PVC lowers the processing stability. 

However this solution is not always convenient and may prevent high productivity and/or the production of intricate forms which require high temperature processing. Fortunately, some fire retardants dramatically increase the flowability of fire retardant plastics melts. For example ABS, flame retarded with F-2016 or F-2016M (brominated epoxy) has much higher flowability, melt flow index (MFI), and spiral flow index, than virgin ABS (Fig. 1). 

T. Handa, T. Nagashima and N. Ebihara, Synergistic Action of Sb2(>3 with Bromine-Containing Flame Retardants in Polyolefins. II. Structure-Effect Relationships in Flame Retardant Systems," J. of Fire Retardant Chemistry,, 37 (1981). ... 

Flame retardants, 11 447-454, 459-479. See also Fire retardant entries Halogenated flame retardants Phosphorus flame retardants antimony compounds in, 3 54 brominated and chlorinated additive, 11 461-470... 

Fire Retardants for Ceftnlosics. Phosphorus-containing materials are by far the most important class of compounds used to imparl durable flame resistance lo cellulose. Flume-retardant finishes containing phosphorus compounds usually also contain nitrogen or bromine or sometimes huth. 

The combination of melamine with hydrated mineral fillers can improve the fire retardancy behavior of PP, eliminating at the same time the afterglow phenomenon associated with these fillers used in isolation.70 Similarly in EVA copolymer, antimony trioxide used in combination with metal hydroxides has been reported to reduce incandescence.56 Chlorinated and brominated flame retardants are sometimes used in combination with metal hydroxides to provide a balance of enhanced fire-retardant efficiency, lower smoke evolution, and lower overall filler levels. For example, in polyolefin wire and cable formulations, magnesium hydroxide in combination with chlorinated additives was reported to show synergism and reduced smoke emission.71... 

However, the optimum degree of flame resistance can only be achieved by making the resin itself nonflammable. A halogenated form of bisphenol A, such as tetrabromobisphe-nol A, has accomplished this. This resin is formed from the reaction product of epichlorohydrin and brominated bisphenol A. These resins acquire their fire-retardant characteristics through bromine substitution on the phenyl rings of the bisphenol A. 

Other fire retardants used include aluminum hydrate, antimony oxide, and molybdenum compound. Halogenated phosphate esters used in polyurethane foams and bromine compounds used in polyolefin foams are not used in phenolic foams. Flame retardants are used mostly in powder form, and accordingly, their distribution conditions are dependent on their particle size and shape. 

Antimony oxide by itself is essentially useless as a fire-retardant additive. However, in combination with other materials, it is by far the most widely used antimony-containing flame retardant additive. It is generally used with bromine- or chlorine-containing compounds (32). 

Bromine compounds are also used as fire retardants. These compounds are about twice as effective as chlorine compounds on a weight basis, so that significantly lower concentrations are needed. However, bromine compounds are higher in cost than chlorinated compounds and are generally less stable under exposure to heat and light (29). Those compounds containing aromatic bromine are significantly more stable to heat and hydrolysis than the aliphatic type. Examples are decabromodiphenyl oxide (DBDPO), tetrabromobisphenol and tetrabromobisphenol A. A pentabromodiphenyl oxide blend is available for urethane foams and polyesters (34). Aliphatic bromine-type additives are used as flame retardants in plastic foams (polyurethane and polystyrene (33). 

As in polyester resins, reactive halogens containing fire-retardant chemicals are most often used in epoxy materials. Tetrabromobisphenol A is perhaps the most widely used component for flame-retarding epoxy resins. Nara and Matsuyama (24) and Nara et al. (25) described the thermal degradation and flame retardance of tetrabrominated bisphenol A diglycidyl ether compared to the nonbrorainated structure. Their results indicate that bromine acts by vapor-phase as well as condensed-phase mechanisms of flame inhibition. 

Metal hydrates such as aluminium trihydrate or magnesium hydroxide remove heat by using it to evaporate water in their structures, thus protecting polymers. Bromine or chlorine-containing fire retardants interfere with the reactions in flames and quench them. Mixtures of flame retardants antimony trioxide and organic bromine compounds are more effective at slowing the rate of burning than the individual flame retardants alone. 

Furthermore, the human health section of the EU Risk Assessment has concluded that the fire retardant additive TBPBA carries no risks, and the EU Scientific Committee on Health and Environmental Risks (SCHER) has confirmed the EU (Risk Assessment) conclusions that TBPBA presents no human health risk. TBPBA is a brominated flame retardant (used in electrical equipment including computers, televisions, and in printed wiring boards (PWB), and so on [21],... 

Tetrabromobisphenol A di-2-hydroxyethyl ether Tetradecabromodiphenoxybenzene Tetrakis (2-chloroethyl) ethylene diphosphate Tris (2,3-dichloropropyl) phosphate flame retardant, EPS Tribromophenyl allyl ether flame retardant, ethyl cellulose Diphenyl octyl phosphate flame retardant, ethylene copolymers Ethylenebis (tetrabromophthalimide) flame retardant, expandable PS Dibromoethyidibromocyclohexane Tetrabromobisphenol A bis (allyl ether) Tetrabromocyclooctane flame retardant, extruded PS Tetrabromocyclooctane flame retardant, fabrics Antimony pentoxide Methylphosphonic acid, (5-ethyl-2-methyl-2-oxido-1,3,2-dioxaphosphorinan-5-yl) methyl methyl ester flame retardant, fibers Antimony pentoxide Tetrabromoethane flame retardant, filament winding Epoxy resin, brominated flame retardant, film Tetrabromobis (2-ethylhexyl) phthalate flame retardant, fire-retardant material Chlorinated paraffins (C12, 60% chlorine) Chlorinated paraffins (C23, 43% chlorine) flame retardant, flexible PU foam bedding Tetrakis (2-chloroethyl) ethylene diphosphate flame retardant, flexible PU foam furniture Tetrakis (2-chloroethyl) ethylene diphosphate flame retardant, flexible PU foam transportation Tetrakis (2-chloroethyl) ethylene diphosphate flame retardant, flexible PU foams furniture, automobile seating... 

Bromination of vinyl-ester resin imparts fire retardancy as manifested by flame spread and lower RHR [50]. However, this fire-retardant system functions primarily in the gas phase causing incomplete combustion. As such, brominated resins produce dense smoke, and an increase in the yield of CO and HBr. Recent interest in the use of non-halogenated organic-matrix composite materials in US Navy submarines and ships has generated the requirement for significant improvement in the flammability performance of these materials including reduction in the amount of smoke, CO and corrosive combustion products. 

Squires [49] investigated the use of melt blendable phosphorus/bromine flame-retardants in PP woven and non-woven fabrics and carpets. Consistent high quality injection moulded parts met V2 ratings in the UL 94 test. Good results are easily achieved with minimal fire retardant loading or the use of a synergist. 

Fire retardants used in polystyrene (PS) include montmorillonite clay, polytetrafluoro-ethylene (PTFE) [8], bromine-based flame retardants such as brominated bisphenol A [9], brominated phenyl oxide or tetrabromophthalic anhydride, or magnesium hydroxide [10,11]. Sanchez-Olivares and co-workers [12], in their study of the effect of montmorillonite clay on the burning rate of PS and PS-polyethylene terephthalate blends, showed that increased combustion rate accompanied the incorporation of montmorillonite particles in high-impact polystyrene (FlIPS) formulations. 

Flame retardant unsaturated polyesters containing chlorine or bromine Chlorendic acid or dibromoneopentyl glycol (60-70%) with addition of antimony trioxide (8 03), ZnSnOj, or triethyl phosphate as flame retarders, increases the LOl by up to 40% Inherent fire retardancy measured [39]... 

The active species in fire retarding are the halogens, chlorine and bromine, phosphorus, and water. The performance of these primary flame retardants is enhanced by synergists antimony, zinc and other metal salts. Some help to develop a protective char (e.g., phosphorus-based systems), separating the unbumed polymer from the flame and heat source. 

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