Special Uses

The novel polymers (end of 1960s and early 1970s) belong mostly to the HT group and their overall utility is limited. Many appear as special fibers, like aromatic polyamides and polyesters, polyimides and Parylene. The novel structures have rings (either aromatic or heterocyclic), in the main chain (para-phenylene is preferred over meta-phenylene). Substituting C—H bonds 

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A special use for meltblown olefin fiber is in filtration media such as surgical masks and industrial filters (78). The high surface area of these ultrafine filament fibers permits preparation of nonwoven filters with effective pore sizes as small as 0.5 p.m. 

Standards for sulfuric acid, ranging from technical-grade through dmg-, food-, and reagent-grade, to electronic-grade are shown in Table 1. The advances in purity represented by these various grades of chemicals are based on the special uses of the chemicals. 

The most important fields of application for PVDF resias iaclude electric and electronic iadustry products, architectural and specialty finishes, products for the chemical and related iadustries, and rapidly growing specialized uses. 

The main uses for argon are in metallurgical appHcations and in electric lamps. Neon, krypton, and xenon, because of high costs, are limited to specialized uses in research, instmmentation, and electric lamps. There are no significant technical uses for radon. 

In open fibers the fiber wall may be a permselective membrane, and uses include dialysis, ultrafiltration, reverse osmosis, Dorman exchange (dialysis), osmotic pumping, pervaporation, gaseous separation, and stream filtration. Alternatively, the fiber wall may act as a catalytic reactor and immobilization of catalyst and enzyme in the wall entity may occur. Loaded fibers are used as sorbents, and in ion exchange and controlled release. Special uses of hoUow fibers include tissue-culture growth, heat exchangers, and others. 

Apart from lactic and hydroxyacetic acids, other a- and P-hydroxy acids have been small-volume specialty products produced in a variety of methods for specialized uses. y-Butyrolactone [96 8-0] which is the monomeric inner ester of y-hydroxybutyric acid [591-81-17, is a large-volume chemical derived from 1,4-butanediol (see Acetylene-derived chemicals). 

Other multifunctional hydroxycarboxylic acids are mevalonic and aldonic acids which can be prepared for specialized uses as aldol reaction products (mevalonic acid [150-97-0] (13)) and mild oxidation of aldoses (aldonic acids). 

Perfluoroalkyl ether greases thickened with polytetrafluoroethylene (MIL-G-38220 and MIL-G-27617) are used from —40 to 200°C in missiles, aircraft, and appHcations where fuel, oil, and Hquid oxygen resistance is needed (55). Polyphenyl ether greases find special use from 10 to 315°C in high vacuum diffusion pumps and for radiation resistance. 

Liquid Metals. If operating temperatures rise above 250—300°C, where many organic fluids decompose and water exerts high vapor pressure, hquid metals have found some use, eg, mercury for limited appHcation in turbines sodium, especially its low melting eutectic with 23 wt % potassium, as a hydrauhc fluid and coolant in nuclear reactors and potassium, mbidium, cesium, and gallium in some special uses. 

Special uses iaclude oxygen for fuels iatended for long-term unattended service (13). Candles are fired on demand by a pressure sensor ia the oxygen accumulator. Chlorate candles were iacorporated iato backpacks designed for use ia the ApoUo moon missions (14). 

Production statistics on alkanolamines are not available, but they are sold in thousand-ton quantities and are available for bulk shipment except for DMAMP, AB, TRIS AMINO, and AMPD (the latter two being crystalline soHds). TRIS AMINO concentrate is available in bulk. AMPD is manufactured only in low volumes to meet limited demand in certain specialized uses. Similarly, 2-AB is manufactured only to meet demand for one end use. 

Animal Nutrition. Sulfur in the diets of mminant animals is beneficial to the animals growth (see Eeedsand FEED ADDITIVES). Sulfur increases feed intake, cellulose and dry matter digestion, and the synthesis of microbial protein. This results in increased meat, milk, and wool production (43). The special uses for sulfur in agriculture demonstrate a significant and continuing need for increased use of sulfur (44). 

New areas in adsorption technology include carbonaceous and polymeric resins (3). Based on synthetic organic polymer materials, these resins may find special uses where compound selectivity is important, low effluent concentrations are required, carbon regeneration is impractical, or the waste to be treated contains high levels of inorganic dissolved soHds. 

Chlorination. Chlorination kills bacteria and is routinely included in secondary treatment. For some special uses, it gives a water quaUty that is acceptable for blending with other water in storage reservoirs. 

Japan. In Japan, registration of dmgs for aquatic species requires the same data as those required for dmgs on other animals. The Ministry of Agriculture, Eorests, and Eisheries and the Ministry of Welfare control the use of chemicals in aquaculture in Japan (17). The preclinical data requirements include product chemistry, toxicity (acute, subacute, special) using rats and mice, safety to target animals, and metaboHsm. The requirements for clinical data include avadabiHty and residues. As of July 1990, more chemicals were registered for aquacultural use in Japan than in any other country (Table 4). 

BeryUium bromide [7787-46-4], BeBr2, and beryUium iodide [7787-53-3], Bel2, are prepared by the reaction of bromine or iodine vapors, respectively, with metallic beryUium at 500—700°C. They cannot be prepared by wet methods. Neither compound is of commercial importance and special uses are unknown. 

In some areas, mn-of-mine coal is separated into three products a low gravity, premium-priced coal for metakurgical or other special use, a middlings product for possible boiler firing, and a high ash refuse. The complete preparation of coal usuaky requires several processes. 

The Beilby process started in 1891 and by 1899 accounted for half of the total European production of cyanide. In this process, a fused mixture of sodium and potassium carbonates reacts with ammonia ia the presence of carbon. In 1900, the Castner process, in which molten sodium, ammonia, and charcoal react to give a high (98%) grade sodium cyanide, superseded the Beilby process. Sodium cyanide became an article of commerce and soon replaced potassium cyanide in all except special uses. 

Cl Disperse Blue 73/72222-75-2] Cl 63265) is an example of a dye that was developed to improve sublimation fastness for special use, eg, thermosol dyeing or printing. This dye also has a bright shade, excellent lightfastness and good leveling properties. Cl Disperse Blue 73 (113) is prepared as follows, where R = H or CH,. 

Later it was found growing in South America where the Indians used the red dye from the seeds as a body paint. An extract of the seeds appears on the market as annatto. This extract is used in coloring butter, margarine, and cheese such as Leicester cheese. In Mexican and South American cuisine, it finds special use as a flavor and coloring matter. The seeds are sold under the name achiote in many Latin grocery stores and markets. Ann at o is available as an aqueous solution, as an oleaginous dispersion, and a spray-dried powder. 

Specialized training or technical literature by raw material suppliers to address special use or handling requirements. 

Although the majority of NAA applications have been in the area of bulk analysis, some specialized uses need to be mentioned. One such unique application is the measurement of phosphorus in thin films (about 5000 A) of phosphosilicate (PSG) or borophosphosilicate (BPSG) glasses used in VLSI device fabrication. In this case,... 

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