Selecting Materials

The data presented in this book are not intended to be used as a substitute for more up-to-date and accurate information on the specific plastics. Such details can be obtained from in-house sources, testing laboratories, and various institutions or the material s supplier. The data here are provided instead as a comparative guide to help in understanding the performance of plastics and in making the decisions that must be made when developing a logical approach to design when compromises have to be made [1, 10-12, 40, 62-64, 99, 249, 262, 278, 386, 444, 485, 497, 519-36]. 

Material Characteristics Strength and Stiffness Toughness Short-Term Heat Resistance Long-Term Heat Resistance Environ- mental Resistance Dimensional Accuracy in Molding Dimensional Stability Wear and Frictional Properties Point Subtotal Cost Point Total 

Other Crystalline Resins Nylons 6 6/6 6/10, 6/12 Polyester Polyacetal  

Ratings I—most desirable 6—least desirable. Large numbers indicate group classification, small numbers the specific resins within that group. 

Suength and stiffness The ability to resist instantaneous applications of load while exhibiting a low level of strain. Materials that demonstrate a proportionality between stress and strain have been assigned better relative ratings. 

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This book is the result of a number of years experience in the compiling and editing of data useful to chemists. In it an effort has been made to select material to meet the needs of chemists who cannot command the unlimited time available to the research specialist, or who lack the facilities of a large technical library which so often is not conveniently located at many manufacturing centers. If the information contained herein serves this purpose, the compiler will feel that he has accomplished a worthy task. Even the worker with the facilities of a comprehensive library may find this volume of value as a time-saver because of the many tables of numerical data which have been especially computed for this purpose. 

C. Y. Ho, R. W. Powell, and P. E. Liley, Standard Reference Data on the Thermal Conductivity of Selected Materials, part 3, final report NBS-NSR05 Contr. CST-1346, Purdue University, Lafayette, Ind., Sept. 1968. 

The existence of isotope shifts and of tunable lasers with narrow Hnewidth leads to the possibHity of separating isotopes with laser radiation (113,114). This can be of importance, because isotopicaHy selected materials are used for many purposes in research, medicine, and industry. In order to separate isotopes, one needs a molecule that contains the desired element and has an isotope shift in its absorption spectmm, plus a laser that can be tuned to the absorption of one of the isotopic constituents. Several means for separating isotopes are avaHable. The selected species may be ionized by absorption of several photons and removed by appHcation of an electric field, or photodissociated and removed by chemical means. 

Pressure. Standard atmospheric pressure is defined to be the force exerted by a column of mercury 760-mm high at 0°C. This corresponds to 0.101325 MPa (14.695 psi). Reference or fixed points for pressure caUbration exist and are analogous to the temperature standards cited (23). These points are based on phase changes or resistance jumps in selected materials. For the highest pressures, the most rehable technique is the correlation of the wavelength shift, /SX with pressure of the mby, R, fluorescence line and is determined by simultaneous specific volume measurements on cubic metals... 

W. W. Minkler, n Assessment of Selected Materials Issues, National Materials Advisory Board, National Academy of Sciences, Washington, D.C., 1981. 

Pump Materials of Construction In the (memical industry, the selection of pump materials of construction is dictated by considerations of corrosion, erosion, personnel safety, and liquid contamination. The experience of pump manufacturers is often valuable in selecting materi s. See section on materials. 

Presence of Solids When a pump is required to pump a hquid containing suspended solids, there are unique requirements which must be considered. Adequate clear-liquid hydraiilic performance and the use of carefully selected materials of construction may not be all that is required for satisfacdoiy pump selection. Dimensions of all internal passages are critical. Pockets and dead spots, areas where solids can accumulate, must be avoided. Close internal clearances are undesirable because of abrasion. Flushing connections for continuous or intermittent use should be provided. 

If L is a charac teristic dimension of a ciystal of selected material and shape, the rate of growth of a ciystal face that is perpendicular to L is, by definition,... 

TABLE 28-18 Typical Mechanical Properties of Selected Materials... 

Materials selection for low-temperature service is a specialized area. In general, it is necessaiy to select materials and fabrication methods which will provide adequate toughness at all operating conditions. It is frequently necessaiy to specify Charpy V-notch (or other appropriate) qu fication tests to demonstrate adequate toughness of carbon and low-aUoy steels at minimum operating temperatures. 

Select materials of construction that can be used in a wide range of services... 

Osher, J.E., H.H. Chau, G.R. Gathers, R.S. Lee, G.W. Pomykal, and R.C. Weingart (1988), Shock-Wave Studies Using Plastic Flyers Driven by an Electric Gun for Hypervelocity Impact on Selected Materials, in Shock Waves in Condensed Matter 1987 (edited by S.C. Schmidt and N.C. Holmes), Elsevier Science, New York, pp. 673-676. 

Table 8.1. Theoretical Spall Strength of Selected Materials.

Steinberg, D.J., Equation of State and Strength Properties of Selected Materials, Lawrence Livermore National Laboratories Report UCRL MA-106439, Feb. 1991. 

In this chapter we illustrate, using a variety of examples, how the designer selects materials so that they provide him or her with the properties needed. As a first example, consider the selection of materials for a... 

Now for some real numbers. Table 3.1 is a ranked list of Young s modulus of materials - we will use it later in solving problems and in selecting materials for particular applications. Diamond is at the top, with a modulus of lOOOGPa soft rubbers and foamed polymers are at the bottom with moduli as low as 0.001 GPa. You can, of course, make special materials with lower moduli - jelly, for instance, has a modulus of about 10 GPa. Practical engineering materials lie in the range 10 to 10 GPa - a... 

Table 4.14 lists the coefficients of expansion for selected materials of construction. 

Select materials based on their functional suitability to the service environment. Materials selected must be capable of maintaining their function safely and for the expected life of the equipment, and at reasonable cost. 

Because any material may be characterized by some desirable and nondesirable properties with respect to a specific application, the selection of materials is reduced to a reasonable compromise. In so doing, one strives to select materials so that properties correspond to the basic demands determined by the function and operating conditions of the equipment, tolerating some of the undesirable properties. 

However, it should always be remembered that it is bad design practice to select materials on the basis of cost per unit weight. In the mass production industries, in particular, die raw material cost is of relatively little importance. It is the in-position cost which is all important. The in-position cost of a component is the sum of several independent factors i.e. raw material costs, fabrication costs and performance costs. 

From a human factors perspective, the chemistry of the process can be made inherently safer by selecting materials that can better tolerate human error in handling, mixing, and charging. If a concentrated reagent is used in a titration, precision in reading the burette is important. If a dilute reagent is used, less precision is needed. 

Hollow carbon nanotubes (CNTs) can be used to generate nearly onedimensional nanostrutures by filling the inner cavity with selected materials. Capillarity forces can be used to introduce liquids into the nanometric systems. Here, we describe experimental studies of capillarity filling in CNTs using metal salts and oxides. The filling process involves, first a CNT-opening steps by oxidation secondly the tubes are immersed into different molten substance. The capillarity-introduced materials are subsequently transformed into metals or oxides by a thermal treatment. In particular, we have observed a size dependence of capillarity forces in CNTs. The described experiments show the present capacities and potentialities of filled CNTs for fabrication of novel nanostructured materials. 

As the production methods of MWCNTs is very efficient [8] (see Chaps. 2 and 12), it is an advantage to implement a filling procedure after the synthesis. A promising approach to fill CNT cavities, could exploit the capillary properties that have been revealed by Ajayan and lijima [9]. Subsequent studies by Dujardin et al.[10] allowed the estimations of a surface tension threshold in order to select materials that are good candidates to wet and fill CNTs. 

Good indoor air quality, critical for a healthy home, requires effective control of pollutants and moisture. To some extent this can be accomplished by thoughtfully selecting materials that contain low levels of volatile organic compounds and formaldehyde. In addition, hard surfaces that can be easily... 

Gilbert, W., Selecting Materials For Wet Scrubbing Systems, Pollution Engineering, Aug. 1973, p. 28. 

Except for fluid conditions of possible galvanic corrosion, the tins can be any selected material, not necessarily the same as the tube. Some usable tin and/or tube materials are... 

The drilling and well servicing structure manufacturer has carefully designed and selected materials for his or her portable mast. The mast should perform satisfactorily within the stipulated load capacities and in accordance with the instructions. Every operator should study the instructions and be prepared for erecting, lowering, and using the mast. 

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