Polyethylene corrosion resistance

Liquid polyalurninum chloride is acidic and corrosive to common metals. Suitable materials for constmction of storage and handling facilities include synthetic mbber-lined steel, corrosion resistant fiber glass reinforced plastics (FRP), ceramics, tetrafluoroethylene polymer (PTFE), poly(vinyhdene fluoride) (PVDF), polyethylene, polypropylene, and poly(vinyl chloride) (PVG). Suitable shipping containers include mbber-lined tank tmcks and rail cars for bulk shipment and plastic-lined or aH-plastic dmms and tote bins for smaller quantities. Except for aluminum chlorohydrates, PAG products are shipped as hazardous substances because of their acidity. 

Chlorination of natural rubber, involving both addition and substitution (with some cyclization), yields a product with improved chemical and corrosion resistance. Chlorination of polyethylene in the presence of sulfur dioxide results in substituting both chloride and sulfonyl chloride groups into the polymer. A commercially useful material is one which contains about 12 chlorides and one sulfonyl chloride per 40-45 repeating units. This extensive substitution converts the polyethylene, a plastic, into an elastomer by destroying crystallinity. 

Radiation doses up to 108 r. have little effect on tensile strength or other properties at room temperature. Gas permeability is also unaffected. A most striking and useful development is the increased strength above 100°C. of polymers treated with about 107 r. The polymer will withstand 100 to 400 lb./sq. in. at these temperatures, which is sufficient to permit containers to support their own weight. This has opened up new markets for polyethylene as a material for heat-sterilizable containers, pipe liners, motor winding material, corrosion-resistant gaskets, etc. 

A solid plastic may be ground to a solid powder and then used to apply a plastic coating to a metal product, either for decorative reasons (color) or for functional performance such as insulation or corrosion resistance. Plastics most often used in this way include nylon, vinyl, acrylic, polyethylene, polypropylene, and epoxy. Coating without solvents is beneficial both economically and environmentally, and 100 percent utilization of material eliminates waste. After the powder is bonded to the metal surface, it is often reheated to flow into a more uniform coating and, in the case of thermosetting resins, to complete the cure reaction. 

Fluoroboric acid is produced commercially by the reaction of 70% hydrofluoric acid with boric acid. Fluoroborate solutions must be treated like hydrofluoric acid and handled in corrosion resistant equipment consisting of polyethylene, polypropylene, or neoprene-type rubber. The major use of fluoroboric acid is as an intermediate in the preparation of fluoroborate salts. It is also used in electroplating aluminum and in metal cleaning operations. 

This is a huge general category of materials, which includes both thermoplastics and thermosetting polymers. Tabular data on the corrosion resistance of these materials in a wide range of environments are available from a variety of sources. Commonly used materials of construction in the CPI include polyvinyl chloride (PVC and CPVC), polyethylene, polypropylene, polystyrene, polycarbonate, polytetrafluoroethylene (PTFE), fiberglass composite materials, and a variety of epoxies used for coatings or adhesives. 

Protective crack-resistant coatings, based on chlorosulfonated polyethylene (CSPE), are widely known due to their unique crack- and corrosion-resistant properties as compared to other rubbers. These coatings also have high ozone, weather, and wear resistance, as well as excellent mechanical and dielectric characteristics. 

Advanced crack-resistant coatings based on water dispersion of chlorine-sulpho-polyethylene (CSPE, Hypalon ) vulcanized by a Mannich alkali (MA) water solution were obtained. Application of MA as a CSPE structure component makes it possible to produce a vulcanized net of saturated polymer, and thus to develop an ecologically safe, impenetrable crack-resistant coating for any substrata (concrete, metal, plastic, etc.). The coatings can be applied in the aircraft, automotive, shipbuilding, paint, and varnish industries, civil engineering, and so on as a corrosion-resistant material. The optimal coating composition and its mechanical properties have been studied. 

LDPE may stress crack when exposed to nonpolar solvents or surface-active agents. Like hope, this nonlinear polyethylene is resistant to nonoxidizing acids, alkalis, and salts but is attacked by oxidizing corrosives, such as nitric acid. 

The thermoplastics used for corrosion resistance are fluorocarbons, acrylics, nylon, chlorinated polyether, polyethylenes, polypropylenes, polystyrence, and poly (vinyl chloride) important thermosetters used in this field are epoxies, phenolics, polyesters, sflicones, and ureas. AH plastics show useful physical properties. One drawback in the use of plastics is their limited tolerance to temperature. Fluorocarbons are the noble metals of plastics they are corrosion resistant to practicaHy all environments up to 290 C. 

The arrangement of elements in the molecule, the symmetry of the structure, and the polymer chains degree of branching are as important as the specific elements contained in the molecule. Polymers containing the carbon-hydrogen bonds such as pol5 ropylene and polyethylene, and the carbon-chlorine bonds such as PVC and ethylene chlorotrifluoroethylene are different in the important property of chemical resistance from a fully fluorinated pol)nner such as polytetrafluoroethylene. The latter has a much wider range of corrosion resistance. 

The two varieties of PE generally used for corrosive applications are EHMW and UHMW. Polyethylene exhibits a wide range of corrosion resistance, ranging from potable water to corrosive wastes. It is resistant to most mineral acids, including sulfuric up to 70% concentrations, inorganic salts including chlorides, alkalies, and many organic acids. It is not resistant to bromine, aromatics, or chlorinated hydrocarbons. Refer to Table 2.27 for... 

PAN has corrosion resistance properties similar to those of pol)/propylene and polyethylene. 

Other virtues include light weight, good electrical and thermal insulation, and in some cases, corrosion resistance, especially where dilute acids and alkalis are concerned. Their low modulus is useful for packaging film applications. Polyethylene comes in several varieties and some of them are quite tough. 

The shape of the 1910 canteen also became the standard that is still represented by today s molded polyethylene 1-quart (0.95-1) canteen, NSN 8465-00-889-3744 (Fig. 14.3). The 1910 1-qnart shape went through material changes thronghout its life cycle. Aluminum, corrosion-resistant steel, plastic and porcelain were used at different periods of the canteen s history. During World War II, aluminum was... 

All the metal parts (pump, hot piping, condenser tubes etc are made of Hastelloy C-276 or equivalent after testing the corrosion resistance) The valves and cold water piping could be made of polypropylene or high-density polyethylene. 

Polyethylene exhibits a wide range of corrosion resistance—ranging from potable water to corrosive wastes. It is resistant to most mineral acids, including sulfuric up to 70% concentration, inorganic salts including chlorides, alkalies, and many organic acids. 

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