Brominated phosphate ester flame retardants

Brominated Phosphate Ester Flame Retardants for Engineering Thermoplastics... 

Brominated phosphate heated in a glass tube in air at 300°C for 30 minutes remains a water-white liquid. This was compared with commercial bromine-containing flame retardants which melt they all turn color. The excellent color stability of this brominated phosphate ester makes it suitable for the high temperature processing of engineering plastics. 

Once ignited they produced considerable amounts of heat and smoke. Flame retarded flexible PU foams became available in 1954-55, i.e. within a few years of flexible PU foams becoming available in commercial quantities(22). These FR PU foams contained trichloroethyl phosphate or brominated phosphate esters and resisted ignition from small flame sources. Unfortunately they may burn when subjected to a larger ignition source or when covered by a flammable fabric and may then produce as much heat and more smoke than the standard grade of PU foam(3). This was identified by UK room tests in the early 1970 s and has been confirmed more recently by furniture calorimeter tests at the NBS(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... 

Commercially available flame retardants include chlorine- and bromine-containing compounds, phosphate esters, and chloroalkyl phosphates. Recent entry into the market place is a blend of an aromatic bromine compound and a phosphate ester (DE-60F Special) for use in flexible polyurethane foam (8). This paper describes the use of a brominated aromatic phosphate ester, where the bromine and phosphorus are in the same molecule, in high temperature thermoplastic applications. 

We previously reported that brominated aromatic phosphate esters are highly effective flame retardants for polymers containing oxygen such as polycarbonates and polyesters (9). Data were reported for use of this phosphate ester in polycarbonates, polyesters and blends. In some polymer systems, antimony oxide or sodium antimonate could be deleted. This paper is a continuation of that work and expands into polycarbonate alloys with polybutylene terephthalate (PBT), polyethylene terephthalate (PET) and acrylonitrile-butadiene-styrene (ABS). 

Three flame retardants were compared in this study, namely, a brominated polycarbonate oligomer (58% bromine), a brominated polystyrene (68% bromine), and a brominated triaryl phosphate ester (60% bromine plus 4% phosphorus). These are described in Table I. Figures 1 and 2 compare the thermal stability of the brominated phosphate with commercial bromine-containing flame retardants by thermogravimetric analysis (TGA) and by differential scanning calorimetry (DSC). The brominated phosphate melts at 110°C and shows a 1% weight loss at 300°C. Brominated polycarbonate and brominated polystyrene are polymeric and are not as volatile at elevated temperatures as the monomeric flame retardants. 

Figure 4. Flame Retarding Polycarbonate/PET Polyester Alloy 1. brominated polycarbonate oligomer 2. brominated polystyrene 3. brominated aromatic phosphate ester...

Halogenated phosphate esters (26) and many other types of flame retardants such as phosphorous-containing compounds including chlorine and/or bromine were extensively reviewed by Hilado (154). 

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. 

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]. 

Saturated halogenated phosphoric esters can be admixed to polyacrylates as additive flame-retardants in a proportion of 30 to 40 per cent, or 12 to 15 per cent when chlorinated (such as tris(chloroethyl) or bis(chloroethyl) phosphates) or brominated (as with tris(bromoethyl) phosphate) agents are used. These additives also act as plasticizers. 

There is an evolving concern about the use of some particular organophosphates such as tricresyl phosphate, tri-n-butyl phosphate, and triphenyl phosphate [94,108-110]. Animal studies have shown that these phosphate esters can cause allergies, learning problems, and deterioration in sperm production and can influence the white and red blood cell counts of humans [109]. In a recent publication [110], levels of flame retardants in indoor air at electronics scrap recycling plant and other work environments were considered 15 brominated FRs and 9 organophosphorus compounds were analyzed. Although the measured concentrations found in all... 

Phosphorus containing flame retardants are used as phosphates, phosphonates, phosphines and phosphinic oxides. Halogen-containing phosphate esters such as bromine and chlorine in the form of tris (halogen alkyl) phosphates are popular [33]. The effects of phosphorus and brominated additives on flexible PU foam were compared [179]. Melamine has broad utility as a flame retardant additive in flexible PU foams [180]. 

Flame Retardant n (1947) A material that reduces the tendency of plastics to burn. Flame retardants are usually incorporated as additives during compounding, but sometimes applied to surfaces of finished articles. Some plasticizers, particularly the phosphate esters and chlorinated paraffins, also serve as flame retardants. Inorganic flame retardants include antimony trioxide, hydrated alumina, monoammonium phosphate, dicyandiamide, zinc borate, boric acid, and ammonium sulfamate. Another group, called reactive-type flame retardants, includes bromine-containing polyols, Chlorendic acid and anhydride, tetrabromo- and tetrachlorophthalic anhydride, tetrabromo bisphenol A, diallyl chlorendate, and unsaturated phosphonated chlorophenols. A few neat resins, such as PVC and the fluoro- and chlorofluo-rocarbons, are flame-retardant (Elias, H (2003) An introduction to plastics. Wiley, New York Modem plastics encyclopedia. McGraw-Hill/Modem Plastics, New York, 1986 1990, 1992, 1993 editions). See Flammability. 

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