Constituent materials, physical properties

Comparable fuels. In order to promote the recycling of materials with high fuel values, certain materials that are burned as fuels are excluded from the definition of solid waste, provided that they meet certain specifications (i.e., are of a certain degree of purity). This is to ensure that the material does not exceed certain levels of toxic constituents and physical properties that might impede burning. Materials that meet this specification are considered comparable to pure or virgin fuels. 

Wood-thermoplastic composites usually consist of wood flour, thermoplastic, and various additives. The wood used in WPCs mostly refers to wood flour or wood fibers. Apart from woody materials, the agricultural plant residues, such as stems, stalks, leave, and seed hairs could also be used as a filler to manufacture WPCs. Generally, wood fiber is the most abundantly used plant fiber due to their extensive use in pulp and paper industries. Commercial composite products typically contain approximately 50 % wood. In some cases, some products only contain little wood, while others contain as much as 70 %. It has been proved that material compositions is highly related to the weathering of WPCs. Therefore, it is imperative to understand the chemical constituents and physical properties of wood. 

The material in this section is divided into three parts. The first subsection deals with the general characteristics of chemical substances. The second subsection is concerned with the chemistry of petroleum it contains a brief review of the nature, composition, and chemical constituents of crude oil and natural gases. The final subsection touches upon selected topics in physical chemistry, including ideal gas behavior, the phase rule and its applications, physical properties of pure substances, ideal solution behavior in binary and multicomponent systems, standard heats of reaction, and combustion of fuels. Examples are provided to illustrate fundamental ideas and principles. Nevertheless, the reader is urged to refer to the recommended bibliography [47-52] or other standard textbooks to obtain a clearer understanding of the subject material. Topics not covered here owing to limitations of space may be readily found in appropriate technical literature. 

Wood is a composite material that is made, up basically of a mixture of three main constituents, cellulose, hemicellulose, and lignin (see Textbox 54), all of them biopolymers synthesized by the plants, which differ from one another in composition and structure (see Textbox 58). The physical properties of any type of wood are determined by the nature of the tree in which the wood grows, as well as on the environmental conditions in which the tree grows. Some of the properties, such as the density of wood from different types of trees, are extremely variable, as can be appreciated from the values listed in Table 71. No distinctions as to the nature of a wood, whether it is a hardwood or a softwood, for example, can be drawn from the value of its specific gravity. 

Defect populations and physical properties such as electronic conductivity can be altered and controlled by manipulation of the surrounding atmosphere. To specify the exact electronic conductivity of such a material, it is necessary to specify its chemical composition, the defect types and populations present, the temperature of the crystal, and the surrounding partial pressures of all the constituents. Brouwer diagrams display the defect concentrations present in a solid as a function of the partial pressure of one of the components. Because the defect populations control such properties as electronic and ionic conductivity, it is generally easy to determine how these vary as the partial pressure varies. 

Another approach is to consider petroleum constituents in terms of transportable materials, the character of which is determined by several chemical and physical properties (i.e., solubility, vapor pressure, and propensity to bind with soil and organic particles). These properties are the basis of measures of teachability and volatility of individual hydrocarbons. Thus, petroleum transport fractions can be considered by equivalent carbon number to be grouped into 13 different fractions. The analytical fractions are then set to match these transport... 

The paramount advantage of molecular solids over their more classical inorganic counterparts is that their constituents, the building blocks, are molecules or clusters that can be designed and synthesized in other words they can be intentionally modified. Therefore, we can talk about molecular and crystal engineering and the goal is to be able to produce materials with predetermined physical properties. We are not yet at this desired level but the scientific and technical bases are certainly at hand. 

There are no recorded data to indicate that materials of this type would alter the stiffness of the concrete into which they are incorporated. However, the fact that these materials are associated with the matrix/air interface, and not the cement hydrates themselves, would suggest that the physical properties of the bonding constituents of the hardened cement would remain unchanged. 

Thermal desorption technologies have several potential limitations. Inorganic contaminants or metals that are not particularly volatile will not be effectively removed by the process. If chlorine or another chlorinated compound is present, some volatilization of inorganic constituents in the waste may also occur. Caution should also be taken regarding the disposition of the material treated by thermal desorption because the treatment process may alter the physical properties of the material. 

As many physical properties of the actinide metals depend significantly on the sample purity, refining of the metals is mandatory. The choice of the refining methods is determined by the chemical reactivity of the actinide metal in the presence of the constituents of air, by high temperature reactions with crucible materials, by the specific radioactivity and the availability of the actinide elements. 

Identification of the constituents of complex materials such as coal may proceed in a variety of ways but generally can be classified into three methods (1) spectroscopic techniques, (2) chemical techniques, and (3) physical property methods whereby various structural parameters are derived from a particular property by a sequence of mathematical manipulations. It is difficult to completely separate these three methods of structural elucidation, and there must, by virtue of need and relationship, be some overlap. Thus, although this review is more concerned with the use of spectroscopic methods applied to the issues of coal structure, there will also be reference to the other two related methods. 

In order to keep also the physical properties for the smeared body, such as the material compressibility or incompressibility of the constituents involved, the mixture theory is restricted by the concept of volume fractions. Therefore, the volume V of the control space is divided into the partial volume fractions n . The sum of the volume fractions has to fill the whole control space. With the concept of volume fractions we obtain the partial density pa for the constituents... 

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