Eric R. Larsen

Thermal Stability of Fire Retardants: I, Hexabromocyclododecane (HBCD

The decomposition kinetics of hexabromocyclododecane (HBCD), a flame retardant used in foamed polystyrene, were studied by monitoring the rate of HBr formed at temperatures between 180-240°C. Samples from five suppliers, and from two lots from three of the suppliers, were evaluated. There were sig nificant differences in the decomposition rates, which appeared to be related to the finishing end of the manufacturing process.

The Effects of Deuteration on the Metabolism of Halogenated Anesthetics in the Rat

The authors studied the effects of substituting deuterium for hydrogen in several volatile anesthetics on their metabolism in the Fischer rat. Substitution of deuterium in the ethyl portion of methoxyflurane increased the metabolic production of fluoride ion by 19 per cent when administered at a concentration of 0.05 per cent. Total replacement of hydrogen by deuterium resulted in a 29 per cent decrease in the amount of fluoride produced, while deuteration of only the methoxyl group produced a 33 per cent decrease in fluoride produced. Deuteration of halothane resulted in a 15 or 26 per cent decrease in serum bromide at 0.75 per cent or 1.0 per cent, respectively. Deuteration in the ethyl portions of enflurane and two experimental agents, CF2HOCF2CFBrH and CF2HOCF2CCl2H resulted in 65, 76, and 29 per cent decreases in urinary fluoride, respectively. Anesthesia with deuterated chloroform at a concentration of 0.36 per cent produced a 35 per cent decrease in serum glutamic pyruvic transaminase (SGPT). It is concluded that deuteration of volatile anesthetics changes their metabolism, in most cases producing decreases in metabolism. This effect may lessen the organ toxicity believed to occur with some of these anesthetics.

Thermal Stability of Fire Retardants:* V. Decomposition of Haloalkyl Phosphates under Polyurethane Processing Conditions

The thermal decomposition of a series of commercial FR agents used in polyurethane was studied in dilute solution in bibenzyl at temperatures com monly found in the center of large, slab stock buns. At 216°C all of the haloalkyl phosphates containing the XCH2CYHO- groups, where X is Cl or Br and Y is H or ClCH2-, decomposed at similar rates, i.e., they all gave first order rate constants between 1.0 and 5.8 x 10 -4 min-1. The addition of toluene diamine to the solution increased the rate of acid evolution from the reacting mixture by a factor of at least ten and in one case by a factor of sixty. The amine is postulated to attack the C-X bond to produce a secondary amine hydrohalide salt which releases hydrogen halide at elevated temperatures. Pentabromodiphenyl oxide was found to be stable under both sets of condi tions. Tris (2,3-dibromopropyl) phosphate, in contrast, undergoes decomposition via a free radical mechanism similar to that of vicinal dibromoalkanes. Tribromoneopentyl phosphate was stable at 216°C, though it decomposed slowly at 234 °C. In the presence of the amine, TBNPP decomposed with the liberation of tribromoneopentyl alcohol and minor amounts of HBr.

Thermal Stability of Fire Retardants:* III, Decomposition of Pentabromochlorocyclohexane and Hexabromocyclododecane under Processing Conditions

The thermal decomposition kinetics of several aliphatic FR agents contain ing vicinal bromines were studied under temperature conditions, i.e., 200-226 °C., commonly found in extruders. The reactions were monitored by the rate of HBr evolution and by the formation of trans-stilbene in dilute (1.8-10 wt.% agent) bibenzyl solutions. The measured reaction rate constants (kHBr ) were found to include a free radical component (kHBr 1) and an ionic com ponent (kHBr 2) resulting from the homolytic cleavage of a carbon-bromine bond and from an iron or zinc induced reaction, respectively. Of the primary agents used in polystyrene, pentabromochlorocyclohexane was found to decompose at about three times the rate of hexabromocyclodo decane at any given temperature.

Thermal Stability of Fire Retardants: IV. Decomposition of Aryl Bromo Ethers Under Process Conditions

Thermal decomposition kinetics were determined for several brominated phenyl allyl ethers, for several brominated diphenyl oxides, and for several miscellaneous compounds used in the manufacture of fire retardant thermo plastics. The decompositions were carried out using bibenzyl as a model for the polystyrene system and at agent loadings of 10 wt.%. The diphenyl oxide deriv atives were stable at reaction temperature (234 ° C) having reaction rate con stants of < 5 x 10-6 min-1. The phenyl allyl ethers underwent rapid decomposi tions with rate constants of 3 to 4 x 102 min 1. The reaction of these ethers is primarily free radical in nature and generates radicals via the homolytic cleavage of the ether linkage.

Single exposure of rats to the vapors of trace substances in methoxyflurane

The question of the acute inhalation toxicity of real and potential trace substances in methoxyflurane was studied by exposing rats to the vapors of 9 compounds. None of the compounds were of the same order of toxicity as 2,3-dichloro-1,1,1,4,4,4-hexafluoro-2- butene, which was run as a standard. The compounds were found to fall in the following order when ranked from least acutely lethal to most acutely lethal toward rat CClF2CH2Cl, CCl3CClF2, CF2CHCl, CH3OCOOCH3, CH3OCF2CH2Cl, CClF2CHCl2, CHCl2COOCH3, CCl2CF2, and CH2ClCOOCH3.

Thermal Stability of Fire Retardants: II Pentabromochlorocyclohexane

The kinetics of the thermal decomposition of pentabromochlorocyclohexane (PBCCH), a flame retardant employed in foamed polystyrene, were determined by monitoring the rate of HBr/Br 2 evolution at temperatures between 195-240°C. The early stage of the decomposition is catalyzed by iron. The acti vation energy for the initial decomposition is approximately 32 Kcal/mole. The principle organic decomposition products are dibromo-, bromochloro-, and tri halobenzenes.

Halogenated Flame Extinguishants – Some Additional Support for the Physical Mechanism:

In previous papers it was argued that the halogens, as flame extinguishants, act as heat sinks in the same manner as nitrogen although they do enter the combustion chemistry. Thus they act, as extinguishants, as heat sinks although, because of their fuel content, they may also add energy to the system.