Halogen-containing polyolefins

CORRELATING PRECISELY DEFINED PRIMARY STRUCTURE WITH CRYSTALLINE PROPERTIES IN HALOGEN CONTAINING POLYOLEFINS... 

Nowadays, the development of TPEs concern many branches of macromol-ecular chemistry cationic and radical polymerizations, chemical modification, enzymatic catalysis or the use of microorganisms. Their respective contributions are analyzed in Section 2. The elastomers based on halogen-containing polyolefins [37] and those prepared by dynamic vulcanization [38] are also included in the TPE family. More information on these materials and techniques is given in Section 2. 

Hofmann G H (1996) Thermoplastic elastomers based on halogen-containing polyolefins, in Thermoplastic Elastomers (Eds. Holden G, Legge N R, Quirk R P and Schroeder H E) Hanser/Garner Publications, Munich, Vienna, New York, Ch. 6, p. 129. 

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. 

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). 

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. 

Aliphatic or side-chain aromatic hydrocarbon polymers (polyolefins and polystyrene) give no char while the CR percentage of main-chain aromatic, condensed aromatic, heterocyclic (high-temperature) polymers may be as high as 70%. Halogen-containing polymers are outside the scope of the above relation. 

With halogen-containing systems, zinc borate can partially or completely replace the antimony synergist in PVC, notably wire and cable, wallcoverings, roof membranes and tarpaulins. It is also effective in polyolefins, elastomers, polyamides and epoxy polymers while, in halogen-free systems, it can be used in conjunction with alumina trihydrate, magnesium hydroxide or red phosphorus. 

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... 

Blends based on halogen-containing polymers are also significant [30-32]. Those based on halo-genated polyolefin/ethylene interpolymer blends are claimed to be single-phase systems [32]. They are often used where solvent and fire resistance is important. PVC/nitrile rubber/dioctyl phthalate blends are used in similar applications and also in footwear [30-32]. 

Polyolefins such as polyethylene and polypropylene contain only C—C and C—H bonds and may be considered as high molecular weight paraffins. Like the simpler paraffins they are somewhat inert and their major chemical reaction is substitution, e.g. halogenation. In addition the branched polyethylenes and the higher polyolefins contain tertiary carbon atoms which are reactive sites for oxidation. Because of this it is necessary to add antioxidants to stabilise the polymers against oxidation Some polyolefins may be cross-linked by peroxides. 

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 ... 

Antimony pentoxide, as an additive for plastic materials such as polyolefins and ABS, is produced in predispersed form containing halogen compounds and a polymeric binder which has a low melting index to aid incorporation. 

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. 

A UV stable iV-alkoxy hindered amine additive containing no halogen offers flame retardancy at surprisingly low concentrations. It synergises with conventional bromine- and phosphorus-containing FRs to provide improved performance in polyolefin fibre and moulding applications. 

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