Halogenation of polymers

Military Application and Aerospace Wires. Depending on the specific appHcation, a variety of polymers can be considered PVC, polyamides, PTEE, etc (Eig. 3). Navy shipboard specifications require cables with dame retardancy, low smoke emission during fire, and containing no halogen. 

Halogenated intermediates, dibromoneopentyl glycol [3296-90-0] (DBNPG), and alkoxylated derivatives of tetrabromobisphenol A are used extensively in flame-retardant apphcations. Similar properties can be derived from halogenated dibasic acids, chlorendic anhydride [115-27-5] (CAN), and tetrabromophthahc anhydride [632-79-1] (TBPA). Processes can be used to produce brominated products by the in situ bromination of polymers derived from tetrahydrophthahc anhydride. 

Table 1. Phase Behavior of Halogenated Polymers With Families of Polymers Containing Ester Units, ...

The designation miscible indicates that some (not all) members of the family have been reported miscible with the indicated halogen-containing polymer. 

A/-Chloro fatty acid amides have been synthesized from the direct halogenation of the amide in boiling water (28). They are useful as reactive intermediates for further synthesis. Fluorination has also been reported by treating the fatty amide with fluorine-containing acid reagents at 200 °C to reach a fluorinated amide with less reactivity toward fluorocarbon polymers (29). 

Butyl and Halobutyl Rubber. Butyl mbber is made by the polymerization of isobutylene a small amount of isoprene is added to provide sites for curing. It is designated HR because of these monomers. Halogenation of butyl mbber with bromine or chlorine increases the reaction rate for vulcanization and laminates or blends of halobutyl are feasible for production of mbber goods. It is estimated that of the - 100 million kg of butyl (UR) and halobutyl (HIIR) mbber in North America, over 90% is used in tire apphcations. The halogenated polymer is used in the innerliner of tubeless tires. Butyl mbber is used to make innertubes and curing bladders. The two major suppHers of butyl and halobutyl polymers in North America are Exxon and Bayer (see ELASTOLffiRS,SYNTHETIC-BUTYLrubber). 

The radiation sensitivity of polymers and monomers is characterized by a G value the number of radicals formed per 100 e.v. (16 aJ) absorbed. Radiation sensitive groups include -COOH, C-halogen, -S02-, -NH2 and -C=C, Radiation resistant groups are aromatic rings. It appears that the presence of aromatic moieties also offers some degree of radiation protection to the polymer chain as a whole. 

The chloride ion is one of the most frequently analysed by IC, e.g. following up combustion of polymers [854,855] similar analyses were reported for the bromide ion [854,855] and nitrite [855]. Analysis of polyester resins for halogens or phosphorous components may be carried out via conversion to halides and phosphates, respectively. 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

Use of higher-performance polymers may suppress the demand for FRs in business machines. Flame retardancy has recently been reviewed [39], as well as the technology of halogen-free FR additives [44]. The future technology of polymer flame retardancy has been described [45]. 

There is substantial data to support reaction sequence [2] and some data suggesting sequence [3] (21, 22) may occur under certain pyrolysis conditions, but no evidence has been published for [3] in the absence of a large excess of polymer substrate. In the case of [2] and [3] it has been suggested that these reactions would be dependent on the carbon-halogen bond strength in the organohalogen component (9). 

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