Resist materials inorganic resists

Inorganic membranes of good radiation and chemical resistance available Separation of dissolved salts from particulate and colloidal material Inorganic membranes available with good chemical and radiation stability can also operate at elevated temperatures Pressure <1 MPa... 

These materials are widely used because they are durable, fire-resistant, and inexpensive when compared with organic materials. Inorganic adhesives are based on compounds such as sodium silicate, magnesium oxychloride, lead oxide (litharge), sulfur, and various metallic phosphates. The characteristics of some of the more important commercial materials are summarized. 

Potting Material We have studied the ozone resistance of various materials for potting, for example, fluoride materials, inorganic material, or others. We have selected siUcone potting material because of its ozone resistance and ease of handling. The new siUcone potting material has at least 5 years ozone resistance under the exposure to 1.0 mg/L of dissolved ozone. 

These materials are widely used because they are durable, fire resistant, and inexpensive when compared with organic materials. Inorganic adhesives are... 

Minerals are generally added to improve wear resistance at minimum cost. The most commonly used are ground limestone (whiting) and barytes, though various types of clay, finely divided siHcas, and other inexpensive or abundant inorganic materials may also perform this function. 

Materials of Construction. GeneraHy, carbon steel is satisfactory as a material of construction when handling propylene, chlorine, HCl, and chlorinated hydrocarbons at low temperatures (below 100°C) in the absence of water. Nickel-based aHoys are chiefly used in the reaction area where resistance to chlorine and HCl at elevated temperatures is required (39). Elastomer-lined equipment, usuaHy PTFE or Kynar, is typicaHy used when water and HCl or chlorine are present together, such as adsorption of HCl in water, since corrosion of most metals is excessive. Stainless steels are to be avoided in locations exposed to inorganic chlorides, as stainless steels can be subject to chloride stress-corrosion cracking. Contact with aluminum should be avoided under aH circumstances because of potential undesirable reactivity problems. 

The gas distribution system can be composed of a network of perforated pipe, slotted or vented concrete block, or metal grating. When there are no space hmitations, single-level filters are used. In regions where footprint space is hmited, hke Japan, multiple-deck filter beds have become commonplace. If inorganic compounds are being treated, corrosion-resistant materials of construc tion are used due to the acidic by-products of the bioreaction. 

The most chemical-resistant plastic commercially available today is tetrafluoroethylene or TFE (Teflon). This thermoplastic is practically unaffected by all alkahes and acids except fluorine and chlorine gas at elevated temperatures and molten metals. It retains its properties up to 260°C (500°F). Chlorotrifluoroethylene or CTFE (Kel-F, Plaskon) also possesses excellent corrosion resistance to almost all acids and alkalies up to 180°C (350°F). A Teflon derivative has been developed from the copolymerization of tetrafluoroethylene and hexafluoropropylene. This resin, FEP, has similar properties to TFE except that it is not recommended for continuous exposures at temperatures above 200°C (400°F). Also, FEP can be extruded on conventional extrusion equipment, while TFE parts must be made by comphcated powder-metallurgy techniques. Another version is poly-vinylidene fluoride, or PVF2 (Kynar), which has excellent resistance to alkahes and acids to 150°C (300°F). It can be extruded. A more recent development is a copolymer of CTFE and ethylene (Halar). This material has excellent resistance to strong inorganic acids, bases, and salts up to 150°C. It also can be extruded. 

Cork compositions 250 Low cost. Truly compressible materials which permit substantial deflections with negligible side flow. Conform well to irregular surfaces. High resistance to oils good resistance to water, many chemicals. Should not be used with inorganic acids, alkalies, oxidizing solutions, live steam. 

This includes inorganic materials such as mica, glass fibre and asbestos etc., impregnated or glued together with varnishes or compositions comprising ordinary organic substances for heat resistance such as oil-modified synthetic resins, bitumen, shellac and Bakelite. 

As may be expected of an amorphous polymer in the middle range of the solubility parameter table, poly(methyl methacrylate) is soluble in a number of solvents with similar solubility parameters. Some examples were given in the previous section. The polymer is attacked by mineral acids but is resistant to alkalis, water and most aqueous inorganic salt solutions. A number of organic materials although not solvents may cause crazing and cracking, e.g. aliphatic alcohols. 

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