Mechanical and Physical Properties

Among the various physical properties of cellulose, such properties are present, which are directly dependent on the degree of crystallinity X], and namely specific volume (V p], specific gravity (Psp], specific heat capacity (Cp], coefficient of thermal expansion (k p], etc. 

Mechanical properties of cellulosic materials of various kinds can depend on different structural characteristics. Cellulose nano-crystallites (NC] are tough and strong constituents. In the 

The mechanical properties of axial orientated non-crystalline domains (NCD) are lower than NC. The maximum axial Young s modulus of NCD is about 70-90 GPa, and the axial TS of these domains is about 4-5 GPa. The mechanical properties of the isotropic amorphous phase of cellulose are poor Young s modulus is about 0.5-0.7 GPa, while TS is about 40-50 MPa. 

The mechanical properties of axial orientated nanofibrils (Z f) can be estimated by equation  

Using Eq. (7.46), it can be found that the axial modulus of orientated nanofibrils is about 120 GPa, and TS is about 5-6 GPa. 

The tensile test shows a steady course of the tensile force-elongation curve, where a linear relationship exists only at low tensile forces. There are only small deviations from a linear course at approximately half-rupture. The tensile strength increases with increasing density. The degree of heat-sealing has an effect here also. 

Owing to their dense, closed surface, untreated foamed PS slabs are acoustically ineffective. Small absorption effects can be achieved by slotting, perforating or corrugating the surfaces. Foamed PS slabs are suitable for footfall-sound insulation only if the dynamic E modulus is lowered by elastifi-cation. 

EPS foam is used in many building projects for thermal insulation and also, more and more often, for soundproofing in new buildings and modernization or renovation work. EPS foam slabs are used for the insulation of walls, roofs, floors and ceilings. Particle sizes between 0.9 and 1.6 mm are preferably used for this application. 

Another system of insulation is the use of EPS molded foam parts (insulated concrete forms) for a combination of outer and inner wall insulation. A wall is built with these molded foam parts and then filled with concrete. 

For the thermal insulation of roofs, there is a difference between fiat roof and steep roof insulation. The insulation of a nonventilated flat roof is done with EPS insulation elements, which could, also, be pre-laminated with a sealing strip. Steep roof insulation is used in attic conversions for residential purposes. There is a difference between insulation under, on and between the rafters. For the between-rafter insulation, different systems are used to make installation very easy. Slabs from the Styrotect [125] system, tongued and grooved, are cut to size, fitted together and laid between the rafters. Also special wedge systems or the use of elasticated slabs are possible. 

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Material Properties. The properties of materials are ultimately deterrnined by the physics of their microstmcture. For engineering appHcations, however, materials are characterized by various macroscopic physical and mechanical properties. Among the former, the thermal properties of materials, including melting temperature, thermal conductivity, specific heat, and coefficient of thermal expansion, are particularly important in welding. 

Magnesium is employed ki a wide variety of appHcations, based on its chemical, electrochemical, physical, and mechanical properties. The International Magnesium Association (IMA) divides the markets for magnesium kito 10 categories and tracks the volume of primary magnesium shipments to each market area on an annual basis. 

The number of branches in HDPE resins is low, at most 5 to 10 branches per 1000 carbon atoms in the chain. Even ethylene homopolymers produced with some transition-metal based catalysts are slightly branched they contain 0.5—3 branches per 1000 carbon atoms. Most of these branches are short, methyl, ethyl, and -butyl (6—8), and their presence is often related to traces of a-olefins in ethylene. The branching degree is one of the important stmctural features of HDPE. Along with molecular weight, it influences most physical and mechanical properties of HDPE resins. 

Physical and Mechanical Properties. Whereas there are some similarities in the physical and chemical properties between corresponding members of the PGM triads, eg, platinum and palladium, the PGMs taken as a unit exhibit a wide range of properties (2). Some of the most important are summarized in Table 2. 

Table 4. Physical and Mechanical Properties of DADC Homopolymer ...

Plastic working of a metal such as steel is the permanent deformation accompHshed by applying mechanical forces to a metal surface. The primary objective is usually the production of a specific shape or si2e (mechanical shaping), although increasingly it also involves the improvement of certain physical and mechanical properties of the metal (mechanical treatment). These two objectives can be readily attained simultaneously. 

The physical and mechanical properties of steel depend on its microstmcture, that is, the nature, distribution, and amounts of its metaHographic constituents as distinct from its chemical composition. The amount and distribution of iron and iron carbide determine most of the properties, although most plain carbon steels also contain manganese, siUcon, phosphoms, sulfur, oxygen, and traces of nitrogen, hydrogen, and other chemical elements such as aluminum and copper. These elements may modify, to a certain extent, the main effects of iron and iron carbide, but the influence of iron carbide always predominates. This is tme even of medium alloy steels, which may contain considerable amounts of nickel, chromium, and molybdenum. 

Physical and mechanical properties are given in Table 22 (109,110,112—114). The densities reflect the effect of aluminum the Zn- -27% Al aHoy is ca... 

Wear is an economic consideration. Wear resistance generally, but not always, is inversely related to friction level and other desirable performance charactenstics within any class of friction matenal. The objective is to provide the highest level of wear resistance in the normal use temperature range, a controlled moderate increase at elevated temperatures, and a return to the original lower wear rate when temperatures again return to normal. Contrary to common behef, maximum wear life does not require maximum physical and mechanical properties. 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

Physical and Mechanical Properties. The physical properties of chromium are Hsted in Table 2 (8,11—14). 

The preparation of molecular composites by electropolymeriza tion of heterocycles in solution with polyelectrolytes is an extremely versatile technique, and many polyelectrolyte systems have been studied. The advantages of this method include the use of aqueous systems for the polymerization. Also, the physical and mechanical properties of the overall composite depend on the properties of the polyelectrolyte, so material tailorabiUty is feasible by selection of a polyelectrolyte with desirable properties. 

Corrosion Resistance Possibly of greater importance than physical and mechanical properties is the ability of an alloy s chemical composition to resist the corrosive action of various hot environments. The forms of high-temperature corrosion which have received the greatest attention are oxidation and scaling. 

Modifications of the wood surface can be performed by various physical, mechanical and chemical treatments. Chemical treatments especially are performed in order to enhance the dimensional stability, but also for amelioration of physical and mechanical properties or a higher resistance against physical, chemical and biological degradation. 

Titanium, tantalum and zirconium are used for construction in process plants. The principal physical and mechanical properties of these three metals are given in the Table 3.34. 

The precious metals are many times the cost of the base metals and, therefore, are limited to specialized applications or to those in which process conditions are highly demanding (e.g., where conditions are too corrosive for base metals and temperatures too high for plastics where base metal contamination must be avoided, as in the food and pharmaceutical industries or where plastics cannot be used because of heat transfer requirements and for special applications such as bursting discs in pressure vessels). The physical and mechanical properties of precious metals and their alloys used in process plants are given in Table 3.38. 

The physical and mechanical properties of the principal thermoplastics of interest for process plant applications are listed in Table 3.42. Table 3.43 gives typical hydrostatic design stresses for different types of thermoplastic pipe. Plastics widely employed in piping systems are described briefly below. 

Polyester resins, reinforced with glass fibers, are used widely in the construction of process equipment. Some physical and mechanical properties are presented in Table 3.48. Table 3.49 lists various materials used as filler and the properties they impart to different plastics. 

Fluorinated rubbers, copolymers of hexafluoropropylene and vinylidene-fluorides, have excellent resistance to oils, fuels and lubricants at temperatures up to 200°C. They have better resistance to aliphatic, aromatic and chlorinated hydrocarbons and most mineral acids than other rubbers, but their high cost restricts their engineering applications. Cheremisinoff et al. [54] provide extensive physical and mechanical properties data on engineering plastics. A glossary of terms concerned with fabrication and properties of plastics is given in the last section of this chapter. 

Grafting reactions alter the physical and mechanical properties of the polymer used as a substrate. Grafting differs from normal chemical modification (e.g., functionalization of polymers) in the possibility of tailoring material properties to a specific end use. For example, cellulose derivatization improves various properties of the original cellulose, but these derivatives cannot compete with many of the petrochemically derived synthetic polymers. Thus, in order to provide a better market position for cellulose derivatives, there is little doubt that further chemical modification is required. Accordingly, grafting of vinyl monomers onto cellulose or cellulose derivatives may improve the intrinsic properties of these polymers. 

The improved physical and mechanical properties of the wood-plastic composites lead to a diversity of applications, e.g., automotive parts, furniture, construction (e.g., building panel, flooring veneers), toys, cutlery handles, industrial pattern, sports equipment, musical... 

Table 3 Physical and Mechanical Properties of Some Natural Fibers...

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