Polymer chlorinated polyethylene

Many cellular plastics that have not reached significant commercial use have been introduced or their manufacture described in Hterature. Examples of such polymers are chlorinated or chlorosulfonated polyethylene, a copolymer of vinyUdene fluoride and hexafluoropropylene, polyamides (4), polytetrafluoroethylene (5), styrene—acrylonitrile copolymers (6,7), polyimides (8), and ethylene—propylene copolymers (9). 

Chlorinated Polyethylene. Chlorinating polyethylene under pressure results in a polymer having a chlorine content varying from 25 to 42%. The polymer requires the incorporation of carbon black and minerals for achieving good physical properties. The polymers handle like conventional polymers and can be mixed and processed on conventional mbber equipment. 

Unlike most elastomeric polymers, which are made by direct polymerization of monomers or comonomers, chlorosulfonated polyethylene, as the name implies, is made by chemical modification of a preformed thermoplastic polymer. The chlorination and chlorosulfonation reactions are usually carried out simultaneously but may be carried out ia stages. 

DuPont have produced a modified chlorosulphonated polyethylene based polymer (trade name Acsium). In this modified polymer the chlorine content is reduced, but an additional pendant alkyl group is used to restrict the ability of the polymer to crystallise. The result is a polymer with a lower Tg than the conventional CSM polymer. 

The common paraffinic polymers, polyethylene (PE) and polypropylene (PP), are relatively inert to chemicals but are attacked by strong chemical reagents. Thus PE can be chlorinated in the same way that paraffins are. 

PVC formulations are generally ethylene vinyl acetate (EVA) polymer-based, chlorinated polyethylene (CPE)-based, or acrylic-based. The majority of new grades are acrylic-based and are claimed to exhibit greater impact strength than the other two types. 

Polyarylate resin Polyarylether ketone resin Polyester carbonate resin Polyetherimide resin Polyethylene, chlorinated Polyethylene glycol Polyethylene, medium density Poly (p-methylstyrene) Poly (p-methylstyrene), rubber-modified Poly (oxy-1,2-ethanediyloxycarbonyl-2,6-naphthalenediylcarbonyl) resin Poly (oxy-p-phenylenesulfonyl-p-phenyleneoxy-p-phenyleneisopropylidene-p-phenylene) resin Poly (phenyleneterephthalamide) resin Polysulfone resin Poly (tetramethylene terephthalate) Polyvinylidene chloride Potassium sorbate Potato (Solanum tuberosum) starch Silica, colloidal Silicone Sodium N-alkylbenzenesulfonate Sodium bicarbonate Sodium tetraborate pentahydrate Starch, pregelatinized Styrene/acrylates copolymer Styrene/butadiene polymer Styrene/DVB copolymer , 1,1 -Sulfonylbis (4-chlorobenzene) polymer with 4,4 -(1-methylethylidene) bis (phenol) and 4,4 -sulfonylbis (phenol) Synthetic wax Tapioca starch Tetrafluoroethylene/perfluoro (propyl vinyl ether) copolymer Tocopherol Triglycidyl isocyanurate VA/crotonates copolymer Vinyl chloride/ethylene copolymer Wheat (Triticum vulgare) starch... 

A large mrmber of polymeric materials are involved in a web coating. These include poly-virtylchloride, polyurethanes (thermoplastic and thermoset solvent-based and water-based), natural, nitrile, chloroprene, and ethylene-propylene rabbers, silicones, polyethylene (chlorinated and chlorositifonated), polyamide, polyester, acrylic resins, polyvinylal-cohol, polytetrafluroethylene, and ethylene-vinyl acetate copolymer as the main matrix polymers of coating compositions. Most of these polymers are not plasticized or seldom... 

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. 

Chlorinated plastics are polymers that have many chlorine atoms in their molec-nlar chain. Good flame resistance and chemical inertness usually characterize these materials. Examples of such materials are chlorinated polyethylene, chlorinated polyether, chlorinated polyvinyl chloride, and chlorofluorocarbons. 

Because of its structure, PVC is particularly sensitive to heat and is by far the largest user of heat stahilizers. Other vulnerable polymers are chlorinated polyethylene and PVC/ABS blends. The increasing use of engineering plastics in applications involving prolonged exposure to heat also calls for special stabilizer systems. 

Modification of PE by chlorination is a simple technique to change the polarity, to reduce the crystallinity, and to increase the elasticity of the polymer. Partially chlorinated polyolefin waxes were reported to improve stability of asphalt-polymer blends [20, 21], so we elected to prepare and characterize polyethylenes with various degrees of chlorination to improve the polymer Interaction with polar components of asphalt. The extent of chlorination can be used to vary the crystallinity of the polymer additive. The crystalline domains of polyolefins contribute to high temperature reinforcement while their amorphous domains, which exhibit very low glass transition temperatures, contribute additional toughness and ductility at low temperatures to PO/asphalt blends, particularly those prepared from soft asphalts. 

Heat stabilizers protect polymers from the chemical degrading effects of heat or uv irradiation. These additives include a wide variety of chemical substances, ranging from purely organic chemicals to metallic soaps to complex organometaUic compounds. By far the most common polymer requiring the use of heat stabilizers is poly(vinyl chloride) (PVC). However, copolymers of PVC, chlorinated poly(vinyl chloride) (CPVC), poly(vinyhdene chloride) (PVDC), and chlorinated polyethylene (CPE), also benefit from this technology. Without the use of heat stabilizers, PVC could not be the widely used polymer that it is, with worldwide production of nearly 16 million metric tons in 1991 alone (see Vinyl polymers). 

Solubility. Cross-linking eliminates polymer solubiUty. Crystallinity sometimes acts like cross-linking because it ties individual chains together, at least well below T. Thus, there are no solvents for linear polyethylene at room temperature, but as it is heated toward its (135°C), it dissolves in a variety of aUphatic, aromatic, and chlorinated hydrocarbons. A rough guide to solubiUty is that like dissolves like, ie, polar solvents tend to dissolve polar polymers and nonpolar solvent dissolve nonpolar polymers. 

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

Other Accelerators. Amine isophthalate and thiazolidine thione, which are used as alternatives to thioureas for cross-linking polychloroprene (Neoprene) and other chlorine-containing polymers, are also used as accelerators. A few free amines are used as accelerators of sulfur vulcanization these have high molecular weight to minimize volatility and workplace exposure. Several amines and amine salts are used to speed up the dimercapto thiadiazole cure of chlorinated polyethylene and polyacrylates. Phosphonium salts are used as accelerators for the bisphenol cure of fluorocarbon mbbers. 

Dimercapto-l,3,4-thiadiazole derivatives, accelerated by amines, are used to cross-link chlorinated polyethylene. Polyisobutylene containing brominated i ra-methylstyrene cure functionahty can be cross-linked in polymer blends with dimercapto-1,3,4-thiadiazole derivatives accelerated with thiuram disulfides. Trithiocyanuric acid is suggested for use in polyacrylates containing a chlorine cure site and in epichlorohydrin mbbers. 

Chlorinated polyethylene (CPE) has excellent o2one, oil, and heat resistance. In addition chlorinated polyethylene has replaced chloroprene elastomers. CPE has a lower specific gravity than chloroprene compounds and produces compounds that are similar to CR in properties but with lower costs. In addition, due to high levels of chlorine in the polymer, the flame resistance of the compounds of CPE are high. 

Chlorosulfonated Polyethylene. This elastomer is made by the simultaneous chlorination and chlorosulfonation of polyethylene in an inert solvent. The resulting polymer is an odorless, colorless chip that is mixed and processed on conventional mbber equipment. The polymer typically contains 20-40% chlorine and 1% sulfur groups (see ElASTOL RS, SYNTHETIC-Cm OROSULFONATEDPOLYETHYLENE) (8). 

Maxillofacial polymers include the chlorinated polyethylenes, polyethemrethanes, polysiloxanes (see Elastomers), and conventional acrylic polymers. These are all deficient in a number of critical performance and processing characteristics. It is generally agreed that there is a need for improved maxillofacial polymers that can be conveniently fabricated into a variety of prostheses (218,227,228). 

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