Thermal stability/stabilization halogenated additives

When potassium fluoride is combined with a variety of quaternary ammonium salts its reaction rate is accelerated and the overall yields of a vanety of halogen displacements are improved [57, p 112ff. Variables like catalyst type and moisture content of the alkali metal fluoride need to be optimized. In addition, the maximum yield is a function of two parallel reactions direct fluorination and catalyst decomposition due to its low thermal stability in the presence of fluoride ion [5,8, 59, 60] One example is trimethylsilyl fluoride, which can be prepared from the chloride by using either 18-crown-6 (Procedure 3, p 192) or Aliquot 336 in wet chlorobenzene, as illustrated in equation 35 [61],... 

Reactivity of halogen fluorosulfates X0S02F (X=C1, Br, I) is very similar to that of halogen triflates however, all of them have higher thermal stability, and they are distillable liquids [8, 102]. The chemistry of halogen fluorosulfates, including addition to fluoroolefins, has been reviewed [8] here only a short summary of these reactions is given. 

The characteristic properties of zeolites, namely thermal stability, shape selectivity and variable acidity and/or basicity, render them an attractive host for halogenation as well as other organic reactions122,123. Unfortunately, irreversible damage is caused to zeolites upon exposure to wet hydrogen halides which results in loss of catalytic activity. Nonetheless, there are numerous reports on the application of X, Y and L zeolites, sometimes exchanged with various metals, in halogenation reactions in addition to isomerizations and separation of alkyl and aryl halides. 

Polyolefin - Polyolefins are a large class of carbon-chain elastomeric and thermoplastic polymers usually prepared by addition (co)polymerization of olefins or alkenes such as ethylene. The most important representatives of this class are polyethylene and polypropylene. There are branched and linear polyolefins and some contain polar pendant groups or are halogenated. Unmodified polyolefins are characterized by relatively low thermal stability and a nonporous, nonpolar surface with poor adhesive properties. Processed by extrusion, injection molding, blow molding, and rotational molding. Other thermoplastic processes are used less frequently. This class of plastics is used more and has more applications than any other. Also called olefinic resin, olefinic plastic. 

Use as a Base. TBAF has been widely used for a variety of base-catalyzed reactions such as alkylation, elimination, halogenation, Michael addition, " aldol condensation, and intramolecular cycUzations. " It is especially useful when other inorganic bases face solubility problems in organic solvents. The reactions are usually carried out below 100 °C due to the low thermal stability of TBAF. ... 

Halogenated flame-retardants may be either additive or reactive. The additive ones are aliphatic/aromatic or otherwise cyclic halogenated hydrocarbons. Generally their efficiency is inversely related to their thermal stability. The flame-retardant effect of the halogen atom (X) is increased by hydrogens on a vicinal carbon atom (as in aliphatic halogenated compounds) due to the ready scission of HX from the carbon chain. It is obvious, however, that these compounds are poor in thermal stability. The same is true for brominated flame-retardants they are more effective but less stable than chlorinated ones. For this reason, chlorinated paraffins and brominated aromatics are more commonly used as flame-retardants rather than aliphatic bromine compounds. 

Martinswerk of Germany said that its Magnifm flame retardants have been specifically created for applications as flame retardant additives, compared with other magnesium hydroxides that have been manufactured from seawater with the pharmaceutical industry in mind. Magnifin is especially recommended for situations where low smoke emission and a high thermal stability are required from a halogen-free retardant. 

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