Polymer halogenated

The discussion centers on heat stabilizers for PVC because this polymer is the most important class of halogenated polymers requiring these chemical additives. PVC of ideal chemical stmcture (1) should be a relatively stable compound as predicted from model studies using 2,4,6-trichloroheptane [13049-21-3] (2) (1). 

Cables are available in a variety of constmctions and materials, in order to meet the requirements of industry specifications and the physical environment. For indoor usage, such as for Local Area Networks (LAN), the codes require that the cables should pass very strict fire and smoke release specifications. In these cases, highly dame retardant and low smoke materials are used, based on halogenated polymers such as duorinated ethylene—propylene polymers (like PTFE or FEP) or poly(vinyl chloride) (PVC). Eor outdoor usage, where fire retardancy is not an issue, polyethylene can be used at a lower cost. 

Flame and Smoke Retardants. Molybdenum compounds are used extensively as flame retardants (qv) (93,94) in the formulation of halogenated polymers such as PVC, polyolefins, and other plastics elastomers and fabrics. An incentive for the use of molybdenum oxide and other molybdenum smoke and flame retardants is the elimination of the use of arsenic trioxide. Although hydrated inorganics are often used as flame retardants, and thought to work by releasing water of crystallization, anhydrous molybdenum oxides are effective. Presumably the molybdenum oxides rapidly form... 

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

Multifunctional Hydroxy, Mercapto, and Amino Compounds. These are used to cross-link halogenated polymers. Depending on the labihty of the halogen, the cross-linking agents can be capped to reduce reactivity or used in combination with accelerators to increase the rate of reaction. Benzoyl capping is common with hydroxy and mercapto compounds forming the carbamate by reaction with one equivalent of carbon dioxide is used with diamines. 

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). 

These materials are developed from the polyetherimides introduced by General Electric (see also Section 18.14.2). At the time of writing one grade, Ultem Siltem STM 1500, is being offered. It is of particular interest as a material for wire and cable insulation, as it not only has excellent flame resistance coupled with low smoke generation but also avoids possible toxic and corrosion hazards of halogenated polymers. This can be of importance where there are possible escape problems in the event of a fire, such as in tunnels, aircraft and marine (particularly submarine) vessels. 

Mixtures of silver peroxide with 1% of polyisobutene exploded on 3 separate occasions. Use of a halogenated polymer was safe. 

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. 

In general, tin compounds do not exhibit flame-retardant properties in halogen-free polymer systems, unless the composition contains a high inorganic filler loading. However, tin additives often act as smoke suppressants in non-halogenated polymers. 

Table 12 Composition, molecular weight, stoichiometric air-to-fuel ratio (sj, net heat of complete combustion (Ahc T), and maximum possible stoichiometric yields of major products (y,imax) for halogenated polymers... 

Highly halogenated organic compounds such as polychlorinated biphenyls and perchloroethylene appear to be too highly oxidised and low in energy content to serve as sources of electrons and energy for microbial metabolism. Bacteria are more likely to use them as electron acceptors in cell-membrane-based respiration processes [154]. The environmental fate of halogenated polymers such as polyvinylchloride or Teflon may depend on the question of whether it will be appropriate to sustain de-halorespiration processes. 

Thus, it was concluded that, combined the medium reactivity of chloromethyl group and flexible polyether-backbone, PECH is one of the most promising halogenated polymers for the developement of various new functional materials. 

Various halogenated polymers are used as the polymeric initiator for ATRP, for example, vinyl chloride-vinyl chloroacetate and styrene-p-chloromethylstyrene copolymers, bromi-nated butyl rubber, and chlorosulfonated polyethylene [Bomer and Matyjaszewski, 2002 Coskun and Temuz, 2003], (The vinyl chloride units have much lower reactivity for ATRP compared to the vinyl chloroacetate units because of steric reasons.) The density of grafting is adjusted by varying the copolymer composition. 

Carbon Adsorbents with Adjustable Porous Structure Formed in the Chemical Dehydro-Halogenation of Halogenated Polymers... 

Keywords Activated carbon Halogenated polymers Mesopores Ultra-Micropores... 

The low efficiency of this initiator limits its utility for polymerization. However, it has been shown to be highly efficacious for grafting onto and substitution of halogenated polymer substrates (55). 

J. M. J. Frechet, Chemical modification of halogenated polymers under phase transfer conditions, J. 

Most of the polymer modifications incorporating benzo-substituted pyrroles have been done with the dibenzo derivative, carbazole, primarily because of its well-known photocon-ductive properties. The modification reaction often involves a substitution reaction on some halogenated polymer. This substitution reaction can be quite facile. Poly(vinylbenzyl chloride), for example, reacts with the potassium salt of carbazole in DMF to yield the carbazole-functional polymer in 97% yield (76MI11110). 

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