Property requirements

The properties required by jet engines are linked to the combustion process particular to aviation engines. They must have an excellent cold behavior down to -50°C, a chemical composition which results in a low radiation flame that avoids carbon deposition on the walls, a low level of contaminants such as sediment, water and gums, in order to avoid problems during the airport storage and handling phase. 

All properties required by diesel fuel are justified by the characteristics of the diesel engine cycle, in particular the following ... 

Each lubricating oil is composed from a main base stock, into which additives are mixed to give the lubricant the properties required for a given application. 

For any molecule, additivity of atomic properties requires as many variables as there are different atom types contained in the molecule. For example, for acetic add, C2H+O2, three different atomic increments are needed, one each for a carbon, a hydrogen, and an oxygen atom. 

PACKAGING - CONTAINERS FORINDUSTRIAL MATERIALS] (Vol 17) Fiber-dye property requirements... 

Rocket Propellants. SoHd rocket propellants are mostly based on chemically cross-linked polymeric elastomers to provide the mechanical properties required in launchings and the environmental conditions experienced in storage, shipment, and handling (see Elastomers, synthetic). Double-and triple-based nitrocellulose propellants are also employed as rocket propellants. 

Fiber stmcture is a dual or a balanced stmcture. Neither a completely amorphous stmcture nor a perfectly crystalline stmcture provides the balance of physical properties required in fibers. The formation and processing of fibers is designed to provide an optimal balance in terms of both stmcture and properties. Excellent discussions of the stmcture of fiber-forming polymers and general methods of the stmcture characterization are available (28—31). 

Terephthahc acid (TA) or dimethyl terephthalate [120-61 -6] (DMT) reacts with ethyleae glycol (2G) to form bis(2-hydroxyethyl) terephthalate [959-26-2] (BHET) which is coadeasatioa polymerized to PET with the elimination of 2G. Moltea polymer is extmded through a die (spinneret) forming filaments that are solidified by air cooling. Combinations of stress, strain, and thermal treatments are appHed to the filaments to orient and crystallize the molecular chains. These steps develop the fiber properties required for specific uses. The two general physical forms of PET fibers are continuous filament and cut staple. 

For staple, the heat-treated filaments in the form of tow are cut to prescribed lengths and then acetalized to develop crimp on individual cut fibers. A suitable finish is selected from conventional ones and appHed to the acetalized fibers to improve their spinnabiUty and other properties required for the intended use. 

Thermoformability is a property required by the many sheet materials used in the thermoforming industry. These properties are unique for the specific forming methods used, and are best determined by actual thermoforming tests on smaU-scale equipment. The softening or drape temperature of the material, residual stress in the sheet from its manufacture, and its melt strength and viscosity are important parameters relating to this use. 

Cladding and backing metals are purchased in the appropriately heat-treated condition because corrosion resistance is retained through bonding. It is customary to supply the composites in the as-bonded condition because hardening usually does not affect the engineering properties. Occasionally, a post-bonding heat treatment is used to achieve properties required for specific combinations. 

The web materials used to form dmms and cans can be customized to each packaging apphcation. The materials are selected based on the package properties of moisture and humidity resistance, nonstick resistance, or barrier properties required. The adhesives used to bond the phes together include sihcates, poly(vinyl alcohol), and poly(vinyl acetate) (10). Sihcate adhesives are most commonly used in the manufacture of dmm packages. 

Air and Oil Filters. Liquid resole resins are used to coat and penetrate the cellulose fibers of filters and separators in order to increase strength and stiffness and protect against attack by the environment. The type of phenoHc to be used depends on both the final property requirements and the papermaking process. 

Although all of the preceding processes can produce a p—n homojunction, the properties required from the junction and the fabrication costs determine the fabrication method. Methods of making other kinds of junctions are similar to those used to make homojunctions, but the materials on either side of such junctions are dissimilar. 

The coarse, nonpigmentary cmdes are particle si2e reduced by a variety of processes to obtain pigmentary CPC. Since CPCs are utili2ed in a variety of industries and a host of appHcations, the specific property requirements vary widely. A large number of special-purpose types are commercially available designed to provide optimal properties for specific appHcations. 

Relatively few processible polyimides, particularly at a reasonable cost and iu rehable supply, are available commercially. Users of polyimides may have to produce iutractable polyimides by themselves in situ according to methods discussed earlier, or synthesize polyimides of unique compositions iu order to meet property requirements such as thermal and thermoxidative stabilities, mechanical and electrical properties, physical properties such as glass-transition temperature, crystalline melting temperature, density, solubility, optical properties, etc. It is, therefore, essential to thoroughly understand the stmcture—property relationships of polyimide systems, and excellent review articles are available (1—5,92). 

Scrap that is unsuitable for recycling into products by the primary aluminum producers is used in the secondary aluminum industry for castings that have modest property requirements. Oxide formation and dross buildup are encountered in the secondary aluminum industry, and fluxes are employed to assist in the collection of dross and removal of inclusions and gas. Such fluxes are usually mixtures of sodium and potassium chlorides. Fumes and residues from these fluxes and treatment of dross are problems of environmental and economic importance, and efforts are made to reclaim both flux and metal values in the dross. 

The relationship between the stmcture of a molecule and its physical properties can be understood by finding a quantitative stmcture—property relation- ship (QSPR) (10). A basis set of similar compounds is used to derive an equation that relates the physical property, eg, melting poiat or boiling poiat, to stmcture. Each physical property requires its own unique QSPR equation. The compounds ia the basis set used for QSPRs with pyridines have sometimes been quite widely divergent ia respect to stmctural similarity or lack of it, yet the technique still seems to work well. The terms of the equation are composed of a coefficient and an iadependent variable called a descriptor. The descriptors can offer iasight iato the physical basis for changes ia the physical property with changes ia stmcture. 

Vulcani2ation is a chemical process for improving an elastomer compound s performance. However, in most cases not all of the desired properties reach their optimum levels simultaneously. One of the mbber compounder s key responsibiHties is to achieve a balance of the most important property requirements by the proper selection of cure system (chemical) and time—temperature cure cycle (physical). 

Vacuum Processes. More complete control over ladle treatment is achieved by the abiHty to seal a vessel weU enough so that a good vacuum can exist over the steel. Although the expense can be justified for steels with the most difficult property requirements, for many purposes less elaborate treatments are adequate. Many possible configurations exist (21). 

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