Surface treatments chlorination

Fluorine was first produced commercially ca 50 years after its discovery. In the intervening period, fluorine chemistry was restricted to the development of various types of electrolytic cells on a laboratory scale. In World War 11, the demand for uranium hexafluoride [7783-81-5] UF, in the United States and United Kingdom, and chlorine trifluoride [7790-91 -2J, CIF, in Germany, led to the development of commercial fluorine-generating cells. The main use of fluorine in the 1990s is in the production of UF for the nuclear power industry (see Nuclearreactors). However, its use in the preparation of some specialty products and in the surface treatment of polymers is growing. 

Uses. /-Butyl hypochlorite has been found useful in upgrading vegetable oils (273) and in the preparation of a-substituted acryflc acid esters (274) and esters of isoprene halohydrins (275). Numerous patents describe its use in cross-linking of polymers (qv) (276), in surface treatment of mbber (qv) (277), and in odor control of polymer latexes (278). It is used in the preparation of propylene oxide (qv) in high yield with Httle or no by-products (269,279). Fluoroalkyl hypochlorites are useful as insecticides, initiators for polymerizations, and bleaching and chlorinating agents (280). 

If corona, plasma, or flame treatment is chosen as the surface treatment, it is important to bond quickly after the treatment. Waiting several hours will reduce the effectiveness of the treatment. In some cases, attempts to bond 24 h after the treatment can give the same poor bonding results as if the plastic had never been surface treated. If surface oxidation is not possible, priming the surface with a chlorinated polyethylene primer is a second choice [95]. 

The application of surface treatments to mbbers should produce improved wettability, creation of polar moieties able to react with the adhesive, cracks and heterogeneities should be formed to facilitate the mechanical interlocking with the adhesive, and an efficient removal of antiadherend moieties (zinc stearate, paraffin wax, and processing oils) have to be reached. Several types of surface preparation involving solvent wiping, mechanical and chemical treatments, and primers have been proposed to improve the adhesion of vulcanized SBR soles. However, chlorination with solutions of trichloroisocyanuric acid (TCI) in different solvents is by far the most common surface preparation for mbbers. 

The use of chlorination as surface treatment to improve the adhesion of mbbers to polyurethane adhesives was proposed in 1971. The employ of chlorination in the industry is due to its high effectiveness in improving the adhesion of several types and formulations of mbbers, it is cheap and easy to apply. Furthermore, chlorination makes the mbber surface compatible with many adhesives... 

Sometimes primers can take the place of surface treatments. Two examples are with porous substrates and with certain plastic substrates. With weak porous substrates, such as wood, cement, or porous stone, the primer can be formulated to penetrate and bind weakly adhering material to provide a new, tightly anchored surface for the adhesive. Chlorinated polyolefin primers will increase the adhesion of coatings and adhesives to polypropylene and to thermoplastic olefins. The chlorine atoms in the outer surface of the primer increase surface energy and enhance adhesion of adhesives, sealants, and paints. 

Preventive treatments have been of several kinds (L6). The sewage may be treated, e.g. with chlorine to oxidize the sulphides, with lime to raise the pH to above 10, which decreases the activity of the anaerobic bacteria, or with appropriate salts to precipitate the sulphide. Removal of slime and silt, in which the sulphide-forming reactions appear to occur, increase in How and design to avoid turbulence, have been found useful. The service life of the concrete is much increased by using limestone as opposed to siliceous aggregates. Various surface treatments have been used, of which one of the most effective appears to be with Sip4 gas. 

Polymeric fibers are popular for reinforcing concrete matrices because of their low density (more number of fibers for a prescribed volume fraction), high tensile strength, ease of dispersion, relative resistance to chemicals, and relatively low cost compared to other kinds of fibers. Polypropylene and polyolefin fibers are typically hydrophobic, resulting in a relatively poor bond with concrete matrices compared to some other types of fibers. Treatment of polypropylene with an aqueous dispersion of colloidal alumina or silica and chlorinated polypropylene enhances the affinity of these fibers toward cement particles. Treatment of polypropylene fibers with a surface-active agent provides better dispersion of the fibers and a stronger bond between cement and fiber. The earlier attempts at surface treatments of polypropylene fibers have had only limited success and have not been commercially attractive. 

In the case of strongly polluted surface water, chlorination is the first purification step and is carried out after removal of any coarse foreign matter. Sufficient chlorine is added to ensure a free chlorine concentration of ca. 0.2 to 0.5 mg/L in the water after treatment (break-point chlorination). Chlorine reacts with water forming hydrochloric acid and the hypochlorite anion, depending upon the pH. 

A further surface treatment was chlorination of a carbon black and an activated carbon with CI2 gas at 723 K for 6 hours [96]. Saturation is nearly reached at this reaction time. HCl is evolved in the chlorination of carbon blacks, in most cases in a molar quantity that slightly exceeds the quantity of chlorine fixed in the reaction, suggesting that this is a substitution reaction [97]. The bonding mechanism is less clear in the case of activated carbons. The catalytic activity of the activated carbon Anthralur decreased on chlorination, while a small catalytic activity was established in the case of the carbon black Corax 3 (Table 7.7). 

Choice of an appropiate surface treatment and a suitable primer are important because adhesion to the substrates presents difficulties [11.37]. Primers based on modified alkyd resins or two-pack epoxy-resins for derusted ferrous metals mainly contain zinc phosphate and zinc OKide as corrosion protection pigments. Nonferrous metals are first washed with an ammoniacal wetting agent before applying the primer that contains a binder based on synthetic resins (e.g., PVC copolymers, chlorinated rubber) which ensure good adhesion to the substrate. The same primer must be used on zinc or galvanized surfaces because the use of alkyd resins causes embrittlement [11.38] The primed surfaces are largely topcoated with alkyd resin systems. 

During surface treatment prior to paint application, abrasive dust and pyrolysis products produced during the removal of paints and solvents may also be inhaled. The dust produced from corrosion protection agents and some older colored paints is often contaminated with heavy metals. Chlorinated hydrocarbons are still used in paint strippers. 

Replacement of organic solvents with water, especially chlorinated solvents Aqueous emulsion polymerization to replace solvent-based polymerization Surface treatment (modification) process development for water-borne... 

Polypropylene is one of the lightest plastics, with a density of 0.905. The nonpolar nature of the polymer gives PP low water absorption. Polypropylene has good chemical resistance, but liquids such as chlorinated solvents, gasoline, and xylene can affect the material. Polypropylene has a low dielectric constant and is a good insulator. Difficulty in bonding to polypropylene can be overcome by the use of surface treatments to improve the adhesion characteristics. 

These requirements may be satisfied by selecting an appropriate structure and type of fiber for the filter fabric, and by surface treatment. Up until recently, woven cotton, wool fabrics, and felted materials were used extensively in industrial filters. Today, synthetic materials are coming into use. For example, a glass fabric treated with silicones is a good filter material at temperatures of 150-315°C. At lower temperatures (below 150°C), filter fabric materials may be made of Lavsan, Nitron, Kapron, or Khlorin (polyester, polyacrylonitrile, polyamide, and chlorinated PVC fibers, respectively). 

Then the water is filtered again to remove the solid mass of fine particles (called a flocculate or floe ) leftover from the initial filtering treatment. Chlorine is added to kill any bacteria in the water. Then it s run through an activated charcoal filter that absorbs (collects on its surface) and removes substances responsible for taste, odor, and color. Fluoride may be added at this time to help prevent tooth decay. Finally, the purified water is collected in a holding tank, ready for your use. 

Chemical reactions of HDPE not involving oxidation include fluorination, chlorination, and sulfonation. Sometimes molded articles, such as fuel tanks, are given such a surface treatment to increase dilfusional resistance. 

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