Other halogenated polyolefins

Much less stable at heating is poly(vinyl bromide), which starts decomposing as low as 100° C with dehydrobromination. Since the dehydrobromination occurs at lower temperatures (activation energy of only 17 kJ mol ), long chains of unsaturated hydrocarbons are generated and do not decompose until the temperature is further increased. Some literature reports regarding thermal decomposition of these polymers are summarized in Table 6.3.8. 

ethyleive, benzene, and other unidentified minor products 54 

Polymers with saturated carbon chain backbone 

As seen from the pyrogram, only very few compounds were generated during pyrolysis at 600° C, the main process during pyrolysis being depolymerization. The monomer chlorotrifluoroethene (MW = 116), eluting in the above-specified conditions at 4.46 min., forms the only compound identified in pyrolysate. Water present in the pyrogram at 18.49 min. is a contamination, and the trace of styrene at 32.63 min. also may come from impurities in the polymer. 

Another halogenated polyolefin that contains chlorine and fluorine in the molecule is poly(ethylene-a/f-chlorotrifluoroethylene), CAS 25101-45-5. As shown in Section 2.1, the pyrolysis of this polymer takes place with the side chain elimination of FICI and FIF by the following reaction  

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Other thermoplastic elastomer combiaations, ia which the elastomer phase may or may not be cross-linked, include blends of polypropylene with nitrile (30,31), butyl (33), and natural (34) mbbers, blends of PVC with nitrile mbber (35,36), and blends of halogenated polyolefins with ethylene interpolymers (29). Collectively, thermoplastic elastomers of this type ate referred to herein as hard polymer/elastomer combinations. Some of the more important examples of the various types are shown in Table 3. 

In other halogen-containing systems, such as flexible PVC and polyolefins, it is preferable to use the zinc borate in conjunction with antimony oxide for maximum performance. In flexible PVC, for example, the zinc borate alone is not very effective in the Oxygen Index test (Fig. 6), but a combination of the zinc borate and antimony oxide (1 1 ratio) outperforms equal weight of antimony oxide at a total loading of more than 10 phr (4). In the presence of alumina trihydrate (ATH), the beneficial effect of using a combination of the zinc borate and antimony oxide is dramatically increased (Fig. 7). 

Polymers with saturated carbon chain backbone include polyolefins, polystyrenes, halogenated polyolefins, halogenated polystyrenes, polyvinyls substituted with various groups such as -OH, -OR, -0(0)C-R, -C(0)0-R, -C(0)-R, -C5H4N, etc. In this class also are included polyacrylates, polymethacrylates, polymers with ketone groups in the backbone, as well as other polymers with saturated carbon chain backbone. The polymers with a saturated carbon chain backbone form the most important and common class of polymers. 

Some of the halogenated polyolefins are vinyl derivatives such as poly(vinyl chloride) and poly(vinyl fluoride), some are vinylidene derivatives, and others are polymers with even higher levels of halogenation. For example, from monomers of fluorinated ethylenes, the following polymers can be obtained ... 

It shows flame retardancy efficacy in polyolefin fibers, at concentrations as low as 1%. Flamstab NOR 116 shows excellent polymer compatibility and high extraction resistance. It also provides superior UV light and thermal stability to the polymer and shows low interaction with acidic species derived from pesticide residues or other halogenated products. 

Halogenated phosphates are also suitable for polyolefins. They are regularly combined with other halogenated compounds and with antimony trioxide. 

APP and APP-based systems are very effident halogen-free flame retardants mainly used in polyolefins (PE, PP), epoxies, polyurethanes, unsaturated polyesters, phenolic resins, and others. APP is a nontoxic, environment friendly material and it does not generate additional quantities of smoke due to intumescence. Compared to other halogen-free systems, APP requires lower loadings. In thermoplastic formulations, APP exhibits good processability, retention of good mechanical properties. 

Usage of phosphoms-based flame retardants for 1994 in the United States has been projected to be 150 million (168). The largest volume use maybe in plasticized vinyl. Other use areas for phosphoms flame retardants are flexible urethane foams, polyester resins and other thermoset resins, adhesives, textiles, polycarbonate—ABS blends, and some other thermoplastics. Development efforts are well advanced to find appHcations for phosphoms flame retardants, especially ammonium polyphosphate combinations, in polyolefins, and red phosphoms in nylons. Interest is strong in finding phosphoms-based alternatives to those halogen-containing systems which have encountered environmental opposition, especially in Europe. 

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... 

Above 100°C, most polyolefins dissolve in various aHphatic and aromatic hydrocarbons and their halogenated derivatives. For example, polybutene dissolves in benzene, toluene, decalin, tetralin, chloroform, and chlorobenzenes. As with other polyolefins, solubiHty of PB depends on temperature, molecular weight, and crystallinity. 

Other fire retardants used include aluminum hydrate, antimony oxide, and molybdenum compound. Halogenated phosphate esters used in polyurethane foams and bromine compounds used in polyolefin foams are not used in phenolic foams. Flame retardants are used mostly in powder form, and accordingly, their distribution conditions are dependent on their particle size and shape. 

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. 

Phosphorus-containing flame retardants are suitable for polar polymers such as PVC, but for polyolefins their action is not sufficient. In this case they are used together with Sb203 and with halogenated compounds. Alkyl-substituted aryl phosphates are incorporated into plasticized PVC and modified PPO (Noryl) to a great extent for other plastics they are less important. Quaternary phosphonium compounds are recommended as flame retardants for ABS and polyolefins. 

The product also works in non-halogenated systems. It can be used with ATH, MgO, ammonium polyphosphate, silica, silicone polymers or melamine compounds in polyolefins, urethanes, polyamides and others. In the silicon containing systems, Firebrake ZB is understood to form a borosilicate glass at polymer combustion temperatures. 

Zinc borate can be used as a fire retardant in PVC, polyolefins, elastomers, polyamides, and epoxy resins. In hal( en-containing systems, it is used in conjunction with antimony oxide, while in halogen-free systems it is normally used in conjunction with other FRs such as aluminum trihydrate, magnesium hydroxide, or red phosphorus. In a small number of specific applications, zinc borate can be used alone. 

Borates Molybdenum compounds Zinc Borate, Barium Metaborates, Ammonium Fluoroborate, Boric Acid Flexible PVC, polyolefins, unsaturated polyesters, thermoplastic polyesters, epoxies, nylons, urethanes, and phenolics Used in comhination with other retardants for flexible PVC and reinforced polyesters. Behave as synergists with halogen containing compounds CSA Chemical Harwich Chemical Corp. US Borax Chemical Corp. Climax Performance Materials CSA Chemical Sherwin WUhams Chemicals... 

Growing concerns over the problems (real or imagined) associated with organo-halogen flame retardants is now creating further opportunities, especially in other polymers, notably polyolefins and polyamides, where ATH is not ideally suited because of its relatively low decomposition temperature. This has led to a surge of interest in other... 

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