Condensation polymers halogenation

The first fire retardant polyester containing a reactive fire retardant monomer was introduced by the Hooker Electrochemical Corporation in the early 1950 s containing chlorendic acid as the reactive monomer (6). This pioneering development rapidly led to the introduction of variety of reactive halogen and phosphorus containing monomers, such as tetrabromophthalic anhydride, chlorostyrene and tetrabromobisphenol A, which found application in a wide variety of condensation polymer systems. 

Much evidence has been accumulated to show that this amine cross-linking does not occur by a comparatively simple condensation with the polymer halogen group but rather by a more complex three stage process involving ... 

Phosphorus-based flame retardants are usually more suitable for engineering plastics that undergo charring than for commodity polymers. In some plastics, such as PC-ABS or poly(phenylene oxide)-HIPS blends, phosphorus-based flame retardants are more effective then halogenated flame retardants. Antimony trioxide, which is a part of halogen-containing formulations, is a Lewis acid and may destabilize some condensation polymers. Furthermore, the impact properties of engineering polymers may suffer due to the presence of powdery antimony trioxide. 

Either mechanism can be used to describe how antimony—halogen systems operate in both the condensed and vapor phases. In the condensed phase a chat that is formed during the reaction of the polymer, antimony trioxide, and the halogen reduces the rate of decomposition of the polymer therefore, less fuel is available for the flame (16). 

Oxidation is the first step for producing molecules with a very wide range of functional groups because oxygenated compounds are precursors to many other products. For example, alcohols may be converted to ethers, esters, alkenes, and, via nucleophilic substitution, to halogenated or amine products. Ketones and aldehydes may be used in condensation reactions to form new C-C double bonds, epoxides may be ring opened to form diols and polymers, and, finally, carboxylic acids are routinely converted to esters, amides, acid chlorides and acid anhydrides. Oxidation reactions are some of the largest scale industrial processes in synthetic chemistry, and the production of alcohols, ketones, aldehydes, epoxides and carboxylic acids is performed on a mammoth scale. For example, world production of ethylene oxide is estimated at 58 million tonnes, 2 million tonnes of adipic acid are made, mainly as a precursor in the synthesis of nylons, and 8 million tonnes of terephthalic acid are produced each year, mainly for the production of polyethylene terephthalate) [1]. 

Condensation monomers having the benzimidazolin-2-one ring system have found utility as modifiers in polyester synthesis. In particular, halogenated diols (73) and dicarboxylic acids (74) may be incorporated (78MI11100) into polyethylene terephthalate) or poly(butyl-ene terephthalate) at fairly low levels to impart flame retardancy. This can be accomplished without adverse effects upon other polymer properties. 

Boron Mechanism. Boron functions as a flame retardant in both the condensed and vapor phases. Under flaming conditions boron and halogens form the corresponding trihalide. Because boron (rihalides are effective Lewis acids, they promote cross-linking, minimizing decomposition of the polymer into volatile flammable gases. These trihalides arc also volatile thus they vaporize into the (lame and release halogen which Ihen functions as a Maine inhibitor. 

For poly silanes made by Wurtz reaction, the presence of functional groups in polysilane polymers is limited by the vigorous conditions of the sodium condensation reaction. Any substituents that react with molten sodium metal must therefore be introduced after the polymer is synthesized. Halogen atoms can be introduced into alkenylpolysilanes by HBr or HC1 addition reactions, as shown for the 3-cyclohexenyl-ethyl polymers in equation (21).37 Chlorine atoms have also been introduced into arylpolysilanes by chloromethylation, in which -CH2C1 groups are substituted onto phenyl rings in the polymer.38... 

Depending on the reaction conditions, the solvent used and the length of the radical at the Si atom, the hydrolytic condensation of trifunctional halogen-containing compounds drastically changes the structure, composition and properties of polyorganosiloxanes formed as a result of hydrolytic condensation and polycondensation. This leads to the formation of branched (I), ladder (II) or cross-linked molecular structures in the polymer. 

The studies of fire-retardant action of halogenated compounds in the condensed phase were performed mostly on mixtures of chloroparaffin with vinyl polymers such as polyethylene,... 

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