Additives flame retardant replacements

BTBPE is used as an additive flame retardant, replacing octaPBDE, for polystyrene and acrylonitrile-butadiene-styrene products. BTBPE was found in the eggs of birds and especially in the dust and air in plants for the liquidation of electronic waste. Animal studies indicate minimum BTBPE absorption in the digestive tract. The major part of BTBPE is probably excreted, partly as metabolites, such as hydroxylated BTBPE and 2,4,6-tribromophenol. 

The highest atmospheric TBE concentrations were detected in samples from a site in southern Arkansas. It is interesting to note that the only producer of TBE in the United States, Great Lakes Chemical, produces this compound at a facility located in El Dorado, Arkansas, which is 150 km west of this Arkansas sampling site. It is likely that the production of TBE will increase at this site given that Great Lakes Chemical has announced that they will market TBE (trade named FF-680) as an additive flame retardant to replace the discontinued octa-BDE product [60]. 

Polybrominated biphenyls (PBBs) are inert, stable chemicals used primarily as additive flame retardants to suppress or delay combustion. In their use as flame retardants, PBBs were added to polymer materials, but were not chemically incorporated into the polymer matrix and therefore could migrate out of the polymer matrix with time. Hexabromobiphenyl was used as a Are retardant mainly in thermoplastics in electronic equipment housings. Smaller amounts were used as a Are retardant in coating and lacquers, and in polyurethane foam for auto upholstery. After the voluntary ban of hexabromobiphenyl in the late 1970s, polybrominated diphenyl ethers (PBDEs) and other flame retardants were used as replacements. 

Since flame retardants have been recognized as not desirable (although not properly quantified in economic valuation), there is now work on replacing flame retardants with other additives with the same functionality. 

Assuming that equal mass of additives is needed, the CBA shows that it is good for society to replace flame retardants in furniture if ... 

Hence, it is apparent that certain inorganic tin compounds are very effective flame retardants and smoke suppressants for halogenated polymer formulations. Since these additives are generally non-toxic, their potential use as partial or total replacements for existing commercial flame retardants, such as antimony trioxide, is thought to merit serious consideration. 

The replacement of established chemistries with newer ones is one of the classic drivers of change in the chemical industry. One of the current hotbeds of this kind of change is the replacement of brominated flame retardants in polymer formulations. The brominated flame retardants under the most scrutiny have been polybrominated diphenyl ethers, particularly penta- and octabromodiphenyl ether, which have been shown to be persistent in the environment and to bioaccumulate. Great Lakes Chemical is voluntarily phasing out penta- and octa-BDEs by the end of next year. The phaseout is made possible by the clean bill of health granted by EPA for Firemaster 550, a replacement for penta-BDE in flexible PU applications. BRG Townsend claims the phaseout of penta-BDE and octa-BDE is not as earth shattering as would be an exit from deca-BDE, a styrenics additive that is produced in the highest volume of the PBDEs. 

In view of the utility of the aromatic polyesters and the demonstrated effectiveness of the aromatic polyphosphonates as flame retardants, the combination of these two polymers was chosen for this study. In addition, this system provided a composition in which both copolymers and polymer blends could be prepared with identical chemical compositions. The polyesters were prepared from resorcinol with an 80/20 m/m ratio of iso-phthaloyl and terephaloyl chlorides while the polyphosphonates were resorcinol phenylphosphonate polymers. Copolymerized phosphorus was incorporated by replacement of a portion of the acid chloride mixture with phenylphosphonic dichloride. 

WEEE has had a direct affect on flame-retardant use, because flame retardants are used in almost all electrical and electronic equipment to prevent fires from short circuits. This directive lays down rules for disposal and recycling of all electrical and electronic equipment that goes back to the previous incinerator discussion. For flame retardants, this directive affects how the plastic parts, cable jackets, and enclosures are flame retarded. If the plastic cannot be reground and recycled, it must go to the incinerator, in which case it cannot form toxic by-products during incineration. This has led to the rapid deselection of brominated FR additives in European plastics that are used in electronics, or the complete removal of FR additives from plastics used in electronics in Europe. This led, in turn, to increases in electrical fires in Europe, and now customers and fire-safety experts demand low environmental impact and fire safety. However, the existing nonhalogen flame-retardant solutions brought in to replace bromine have their own balance-of-property issues, and so research continues to develop materials that can meet WEEE objectives. 

Polyolefins When used in conjunction with a halogen-based flame retardant, this zinc borate can partially replace antimony oxide (30%-40%) and still maintain the same fire test performance. In addition, it can improve aged elongation properties, increase char formation, and decrease smoke generation. The B203 moiety in zinc borate can also provide afterglow suppression (Table 9.6). 

In EPR formulations, calcium borate was found to be a good replacement for the combination of antimony trioxide with an organic flame retardant Calcium borate, in addition to affecting flame retardation, also reinforces the polymer. Another alternative is based on huntite/hydromagnesite filler. Here, some antimony trioxide and organic flame retardant combination must be added. The huntite/magnesite filler combination cannot, by itself, halt flame spread. ... 

A manufacturer considering using a thermoplastic elastomer would probably first consider one of the thermoplastic polyolefin rubbers or TPOs, since these tend to have the lowest raw polymer price. These are mainly based on blends of polypropylene and an ethylene-propylene rubber (either EPM or EPDM) although some of the polypropylene may be replaced by polyethylene. A wide range of blends are possible which may also contain some filler, oil and flame retardant in addition to the polymers. The blends are usually subject to dynamic vulcanisation as described in Section 11.9.1. 

The electronics industry desires improved flame suppressant additives for microelectronic encapsulants due to bromine induced failure. Epoxy derivatives of novolacs containing meta-bromo phenol have exhibited exceptional hydrolytic and thermal stability in contrast to standard CEN resins with conventional TBBA epoxy resins. When formulated into a microelectronic encapsulant, this stable bromine epoxy novolac contributes to significant enhancements in device reliability over standard resins. The stable bromine CEN encapsulant took about 30% more time to reach 50% failure than the bias pressure cooker device test. In the high temperature storage device test, the stable bromine CEN encapsulant took about 400% more time to reach 50% failure than the standard compound. Finally, the replacement of the standard resins with stable bromine CEN does not adversely affect the desirable reactivity, mechanical, flame retardance or thermal properties of standard molding compounds. 

Trimellitates are the esters of trimellitic anhydride (1,2,4-benzenetricarboxy-lic acid anhydride) and are noted for their low volatility. The most frequently used are trioctyl trimellitate (TOTM) and tri-isononyl trimellitate (TINTM). They are included in plastics which have to function at high temperatures for long periods and for PVC cable insulation in combination with phthalates. Phosphorous oxychloride reacts with various aliphatic and aromatic alcohols and phenols (triphenylphosphate) to produce triesters. Tricresyl phosphate was patented as a plasticizer for PVC in 1933, but was later found to be highly toxic and replaced. In addition to their role as plasticizers, phosphate esters, particularly triphenyl phosphate, function as flame retardants. 

---