Speciality additives

Silicon Nitride. SiUcon nitride is manufactured either as a powder as a precursor for the production of hot-pressed parts or as self-bonded, reaction-sintered, siUcon nitride parts. a-SiUcon nitride, used in the manufacture of Si N intended for hot pressing, can be obtained by nitriding Si powder in an atmosphere of H2, N2, and NH. Reaction conditions, eg, temperature, time, and atmosphere, have to be controlled closely. Special additions, such as Fe202 to the precursor material, act as catalysts for the formation of predorninately a-Si N. SiUcon nitride is ball-milled to a very fine powder and is purified by acid leaching. SiUcon nitride can be hot pressed to full density by adding 1—5% MgO. 

A variety of thermosetting resins are used in SMC. Polyesters represent the most volume and are available in systems that provide low shrinkage and low surface profile by means of special additives. Class A automotive surface requirements have resulted in the development of sophisticated systems that commercially produce auto body panels that can be taken direcdy from the mold and processed through standard automotive painting systems, without additional surface finishing. Vinyl ester and epoxy resins (qv) are also used in SMC for more stmcturaHy demanding appHcations. 

Masonry cements (80) are cements for use in mortars for masonry constmction. They are formulated to yield easily workable mortars and contain special additives that reduce the loss of water from the mortar to the porous masonry units. 

Most of the resin systems used in commodity composites are slight modifications of the standard commercial mol ding grade material. Usually certain selected properties, such as purity or molecular weight range or distribution, are enhanced or carehiUy selected. In addition, special additives, such as flow controllers, thermal stabilizers, or antioxidants, are often added by the resin manufacturer prior to shipment. Many of the conventional or commodity-type resins used in thermoplastic composites are Hsted in Table 1 and the preparation of each of these is described. AH resins and blends described in the hterature are not Hsted, and the synthesis described is not the only procedure available, but is usually the most common commercial process. 

Other special additions are used to deoxidize copper. Such alloys may be preferred in appHcations where embrittlement by hydrogen through reaction with internally dispersed copper oxide particles is a concern, such as in CllO. The most common deoxidized copper is C122, in which phosphoms reacts with copper oxide to form phosphoms pentoxide that can be slagged from the copper while molten. 

S is solution strengthened D, dispersed phase P, precipitation strengthened SA, special addition. 

The formulation of a carrier depends on four considerations (/) the carrier-active chemical compound (2) the emulsifier (J) special additives and (4) environmental concerns. Additional parameters to be considered in the formulation of a carrier product with satisfactory and repeatable performance arise from the equipment in which the dyeing operation is to be carried out. The choice of equipment is usually dictated by the form in which the fiber substrate is to be processed, eg, loose fiber, staple, continuous or texturized filament, woven or knot fabric, yam on packages or in skeins (see Textiles). 

Special additives are often included in a carrier formulation to provide specific properties such as foam control, stabiUty, and fiber lubrication during dyeing. Most important are the solvents used to solubilize the soHd carrier-active chemicals. These often contribute to the general carrier activity of the finished product. For example, chlorinated benzenes and aromatic esters are good solvents for biphenyls and phenylphenols. Flammable compounds (flash point below 60°C) should be avoided. 

Hygroscopic materials, condensation of moisture, or tarry adhesive components possibly causing crusty caking or plugging of the fabric or requiring special additives... 

Before fabrication it is necessary to compound the gum with fillers, vulcruiising agent and other special additives on a two-roll mill or in an internal mixer. 

Extending Agent, inhibitors. Catalytic Solution and Special Additives)... 

Another point is related to the high acidity level of the final solution, which leads to certain limitations in the subsequent technological steps. Specifically, the high acidity of the initial solution eliminates any possibility for selective extraction, i.e. sequential separation of tantalum and then of niobium. Due to the high concentration of acids, only collective extraction (of tantalum and niobium together) can be performed, at least at the first step. In addition, extraction from a highly acidic solution might cause additional contamination of the final products with antimony and other related impurities. In order to reduce the level of contaminants in the initial solution, some special additives are applied prior to the liquid-liquid extraction. For instance, some mineral acids and base metals are added to the solution at certain temperatures to cause the precipitation of antimony [455 - 457]. 

The second problem is that the experimental data indicating a presence of interfacial regions should be carefully considered, avoiding a misinterpretation. In addition to manifestation of a real interface, which is formed due to chain entanglements of the components or a presence of special additives, one should be aware about effects related to tip geometry and a complex local... 

This approach does not preclude gels having special, additional properties of their own due to peculiarities of their molecules. Such an example was in the thixotrophy of borax gels caused by the dynamic equilibrium of the bonds. Even gels that are formed by two apparently different mechanisms have the same fundamental gelling characteristics. For a timely and exhaustive review on gelling systems the reader should refer to the recent work of Whistler and BeMiller (if). 

Electrochemical reaction rates are also influenced by substances which, although not involved in the reaction, are readily adsorbed on the electrode surface (reaction products, accidental contaminants, or special additives). Most often this influence comes about when the foreign species I by adsorbing on the electrode partly block the surface, depress the adsorption of reactant species j, and thus lower the reaction rate. On a homogeneous surface and with adsorption following the Langmuir isotherm, a factor 10, will appear in the kinetic equation which is the surface fraction free of foreign species 1 ... 

Modern casting techniques allow the production of massive steel rolls, which can subsequently be milled directly into plates for the car industry. Exact proportions of carbon and special additives make steel a "high-tech" material. 

From these killings developed the first haphazard procedure. At first the dead were counted — not to record the crimes but to account for inmates who had tried to escape. The prisoners received consecutive numbers on arrival. Every number was issued only once, so that the last number always corresponded to the total number of prisoners who had been in the camp. At first the numbers were tattooed on the left breast, but later, because of their becoming blurred, on the left forearm. Special additional symbols were tattooed on the arms of the Jews, Poles, and Ukrainians. The dead having been counted, they were piled on flat,... 

After products are produced by refining they are further enhanced in a blending unit. In this unit the finished products are made by mixing the components in blending tanks. To gasoline for example, coloring dyes or special additives maybe added. The completed blends are tested and then routed to tank farm storage or shipment. 

Drugs intended for use in either the elderly or the very young have special additional requirements for safety evaluation, in recognition of the special characteristics and potential sensitivities of these populations. For the elderly, these... 

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