Magnesium, combining with bromine

Brominated indan in nylon 6,6 results in a high oxygen index value. A further increase can be achieved by combination with surface-treated magnesium hydroxide.63... 

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... 

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... 

Both intercalated and exfoliated nanocomposites, containing 3-5% of nanoparticles (w/w), reportedly show better or comparable flame resistance compared with plastics filled up to 30-50% with traditional flame retardants. Another way to increase flame retardancy is to combine ATH or magnesium hydroxide with organo-clays. It was reported that organoclays and some classical flame retardants, such as brominated compounds, showed a synergism between them [13]. 

When a PA is to be used in applications requiring self-extinguishing characteristics and flame retardant properties, it is necessary to resort to the addition of a flame retardant. Flame retardant formulations, known in the field of poly(ester)s, can be widely adapted to PAs. Brominated poly(styr-ene) in combination with an antimony compound, such as sodium antimon-ate, can be used." The performance is improved when a minor amount of calcium oxide is added. The thermal stability of these compositions is much better in comparison to formulations with magnesium oxide or zinc oxide. 

Flame Retardants. Hydrocarbon elastomers are flammable and thus require flame retardants if their service conditions include the possibihty of fire. Alumina trihydrate, magnesium hydroxide, and zinc borate are used, because they give off blanketing vapors at high temperatures. Also, typical flame-retardant systems include chlorinated paraffins or brominated aromatic resins in combination with antimony trioxide. 

Occidental Chemicals supplies Dechlorane and Dechlorane Plus, a Diels-Alder adduct of hexachlorocyclopentadiene. It has a wide range of processing temperatures, offers the advantage of lower smoke than brominated equivalents on burning, and is useful at the 15%-18% level in PBT and the polyamides. A synergist such as zinc borate, oxide or stannate is advisable as well. Chlorinated FRs can be combined with magnesium hydroxide in polyolefin wire and cable formulations. 

A 5.5 M solution of bromine in dichloromethane is added dropwise to a vigorously stirred mixture of 19.1 g. (0.097 mole) of hydrazine 1, 75 ml. of dichloromethane, 75 ml. of water, and 22 g. (0.262 mole) of sodium bicarbonate in a 250-ml. flask, until a persistent, positive potassium iodide-starch paper test is obtained (Note 8). Excess bromine is then discharged with aqueous sodium sulfite, and the phases are separated. The aqueous phase is extracted with two 50-ml. portions of dichloromethane, and the combined organic extracts are washed with 30 ml. of water, dried over magnesium sulfate, filtered, concentrated using a rotary evaporator, and distilled to afford 17.3 g. (93% yield) of the diazene 2 as a clear, bright yellow oil, b.p. 95-97° (0.2 mm.) (Note 7). 

A. 2-Bromo-2-cyclopentenone. In a well-ventillated hood, a solution of 18.98 g (231.2 mmol) of 2-cyclopentenone (Note 1) in 150 mL of carbon tetrachloride is added to a 1-L, three-necked, round-bottomed flask fitted with a mechanical stirrer, thermometer, and an addition funnel. The solution is chilled to 0°C with an ice bath and a solution of 40.5 g (253.4 mmol, 13.0 mL) of bromine in 150 mL of carbon tetrachloride is added dropwise during 1 hr. Then a solution of 35.1 g (346.8 mmol, 48.3 mL) of triethylamine in 150 mL of carbon tetrachloride is added dropwise over 1 hr with vigorous stirring while the reaction is held at 0°C. Stirring is continued for an additional 2 hr at room temperature the resulting dark suspension is filtered with suction and the filter cake washed with carbon tetrachloride. The filtrate and washings are combined and washed with two 100-mL portions of 2 N hydrochloride acid, one 100-mL portion of saturated sodium bicarbonate solution, one 100-mL portion of water, and one 100-mL portion of saturated sodium chloride solution. The resultant solution is dried over anhydrous magnesium sulfate, filtered, and the solvent removed under reduced pressure. Distillation of the resultant oil (69-78°C, 1.0 mm) afforded 23.7 g (147.2 mmol, 64%) (Note 2) of a white crystalline solid (mp 36-37°C, lit.2 mp 39-39.5°C) (Note 3). 

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