Flame retardants chlorinated systems

A significant advance in flame retardancy was the introduction of binary systems based on the use of halogenated organics and metal salts (6,7). In particular, a 1942 patent (7) described a finish for utilizing chlorinated paraffins and antimony(III) oxide [1309-64-4]. This type of finish was invaluable in World War II, and saw considerable use on outdoor cotton fabrics in both uniforms and tents. 

Flame-Retardant Applications. The flame resistance of polyolefins, unsaturated polyester, mbber, and many other synthetic materials can be improved by the iaclusion of chloriaated paraffias. The soHd 70% chlorine product is the preferred choice ia most polymeric systems, but the Hquid grades are widely used ia mbbers, polyurethane, and textile treatments. 

It has already been mentioned in Chapter 5 that plasticisers are often replaced in part by extenders, materials which in themselves are not plasticisers but which can be tolerated up to a given concentration in a polymer-plasticiser system. Refinery oils and chlorinated waxes are widely used in PVC for this purpose with the prime aim of reducing cost although the chlorinated waxes may also be of use as flame retardants (q.v.). 

Brominated and chlorinated organic flame-retardants can be analysed using either GC-MS or LC-MS. High resolution systems are required to identify the specific isomers. Quantification by bromine or chlorine content is normally achieved using XRF against standards in the same matrix. 

PMMA - Red Phosphorus System. The initial reaction that was investigated was that between PMMA and red phosphorus (4-51. Phosphorus was chosen since this material is known to function as a flame retardant for oxygen-containing polymers (1 2). Two previous investigations of the reaction of PMMA with red phosphorus have been carried out and the results are conflicting. Raley has reported that the addition of organic halides and red phosphorus to PMMA caused moderate to severe deterioration in flammability characteristics. Other authors have reported that the addition of chlorine and phosphorus compounds are effective flame retardant additives (12). 

Polychlorinated biphenyls (PCBs), known by their trade marks of Arochlor (Monsanto U.S.), Phenochlor (in France), and Clophen (in Germany) are chemically similar to the chlorinated insecticides. Although not used for this purpose, their existence and persistence in the environment is well established. They were used to make more flexible and flame retardant plastics and are still used as insulating fluids in electrical transformers since there is no substitute in this application. They have been made by Monsanto since 1930 and were first discovered as a pollutant in 1966. U.S. production peaked at 72 million lb in 1970 but in 1975 it was down to 40 million Ib/yr because in 1971 Monsanto voluntarily adopted the policy of selling PCBs only for electrical systems. At least 105 PCBs are present in the environment. 

Firebrake . (U.S. Borax Qiem.] Zinc borate flame retardant, smt e suppressant, synergist used in chlorinated pdyesters, PVC plastisois, and epoxy systems. 

Dimethanodil)enzo-(a,e)cydooclane, 1,2,3,4,7,8,9,10,13,13,14,14-dodeca-chloro- 1,4,4a,5,6,6a,7,10,1 Oa, 11,12,12a-dodecahydro-1,4 7,10-Dimethanodiben2o(a,e)oyolooctene, EINECS 236-948-9. Chlorine-containing cycloaliphatic comp-ound. Used as a flame retardant in polymer systems (thermoplastics, thermosets and elastomers) usually combined with antimony oxide as a synergist. Colorless crystals mp >326° soluble in o-dichlorobenzene LDso (rat orl) = 25 g/kg. OxyChem. 

The active species in fire retarding are the halogens, chlorine and bromine, phosphorus, and water. The performance of these primary flame retardants is enhanced by synergists antimony, zinc and other metal salts. Some help to develop a protective char (e.g., phosphorus-based systems), separating the unbumed polymer from the flame and heat source. 

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. 

Other Organohalogens. Thermal instabihty is also a problem in other polymers such as chlorinated polyethylene, chlorinated PVC, polyvinylidene chloride, chlorinated rubber, and chlorinated and brominated flame-retardants. PVC heat stabilizers may help here, too, but require careful adjustment for optimum performance in each system. 

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