Properties, electrical mechanical

An extensive new Section 10 is devoted to polymers, rubbers, fats, oils, and waxes. A discussion of polymers and rubbers is followed by the formulas and key properties of plastic materials. Eor each member and type of the plastic families there is a tabulation of their physical, electrical, mechanical, and thermal properties and characteristics. A similar treatment is accorded the various types of rubber materials. Chemical resistance and gas permeability constants are also given for rubbers and plastics. The section concludes with various constants of fats, oils, and waxes. 

Engineering rework is possible with eutectic and solder materials, but impossible with silver—glass. This constraint severely limits the usefulness of the material. Tables 4 and 5 give the electrical, mechanical, and thermal properties for various adhesives. 

Material property specifications must be written by design and material engineers to control engineering requirements and to control incoming raw material quahty. Material property requirements depend on various ia-use functional needs ia terms of electrical, mechanical, thermal, chemical, optical, and magnetic properties. 

The abiHty of a given material to perform as an electronic embedding encapsulant depends largely on its properties. Ultrapure chemical properties with a low level of mobile ions such as sodium, potassium, and chloride are essential. Furthermore, the material s electrical, mechanical, and rheological properties are critical. 

Electrical and Mechanical Properties. Electrical properties include dielectric strength, dielectric constant, dissipation factor, and volume resistivity these properties can change with temperature and absorbed water. 

The winding insulation must remain intact with respect to both electrical insulating properties and mechanical... 

Because of the geometry, or morphology, of these molecules some can come closer together and more orderly than others. These are identified as crystalline and all others that behave like spagetti as amorphous. Morphology influences such properties as mechanical and thermal, swelling and solubility, specific gravity, and other properties (mechanical, physical, chemical, electric, etc.). 

Tables 7-5 to 7-7 show that there are different orders of magnitude between plastics and metals. Depending on the application, plastics may be formulated and processed to exhibit a single property or a designed combination of electrical, mechanical, chemical, thermal, optical, aging properties, and others. The chemical structure of polymers and the various additives they incorporate provide compounds to meet many different performance requirements.

Die Tg can be determined readily only by observing the temperature at which a significant change takes place in a specific electric, mechanical, or physical property. Moreover, the observed temperature can vary significantly, depending on the specific property chosen for observation and on details of the experimental technique (for example, the rate of heating, or frequency). Therefore, the observed Tg should be considered to be only an estimate. The most reliable estimates are normally obtained from the loss peak observed in dynamic mechanical tests or from dilatometric data (ASTM D-20). 

The first interactive electronic encyclopedia for users of plastics, materials selection is carried out using 3 search routines. The Chemical Resistance Search eliminates materials that cannot meet user specified chemical resistance requirements. The other search routines ( Elimination and Combined Weighting ) eliminate candidate materials based on 72 properties, falling within one of the following groups General and Electrical, Mechanical, Cost Factors, Production Methods and Post Processing. All data is evaluated and based on independent tests conducted in RAPRA s laboratories. 

MIL-P-47136 covers one formulation of plasticized PVC used in the production of flexible tubing, cord, film, sheet, and other various extruded shapes. The Specification requirements are concerned with electrical, mechanical and physical properties and shelf life Refs 1) D. Haft, PATR1592 (1946) 2) H.J. 

When water is used as the immersion liquid, the test is essentially the ASTM Standard Test Method (D570) for Water Absorption of Plastics.( ) Determinations of the relative rate of water absorption are important in evaluating the effects of moisture exposure on such properties as mechanical strength, electrical resistivity, dielectric... 

Thickness (mm) Electrical, mechanical properties, including impact (°C) Electrical, mechanical properties, excluding impact (°C) Electrical properties (°C)... 

The Physical Properties are listed next. Under this loose term a wide range of properties, including mechanical, electrical and magnetic properties of elements are presented. Such properties include color, odor, taste, refractive index, crystal structure, allotropic forms (if any), hardness, density, melting point, boiling point, vapor pressure, critical constants (temperature, pressure and vol-ume/density), electrical resistivity, viscosity, surface tension. Young s modulus, shear modulus, Poisson s ratio, magnetic susceptibility and the thermal neutron cross section data for many elements. Also, solubilities in water, acids, alkalies, and salt solutions (in certain cases) are presented in this section. 

Insulation Integrity. Insulation integrity is a function of an interlayer dielectric/passivant defined by specific electrical, mechanical and passivation properties. The D.C. electrical property of interest is the I-V characteristic which is used to deduce conductivity and breakdown field strength. The corresponding A.C. electrical property is dissipation factor. The pertinent mechanical and passivation properties are, respectively, pinhole density and performance rating as a diffusion barrier to Na" " and H2O. 

The characteristics of the three most common thermoset resin systems used in pultrusion are compiled in Table 11.2 [3]. It is noteworthy that unreinforced polyesters and vinylesters shrink 7-9% upon crosslinking, whereas epoxies shrink much less and tend to adhere to the die. These epoxy characteristics translate into processing difficulties, reduced processing speed, and inferior component surface finish. It is normal practice to use resin additives to improve processability, mechanical properties, electrical properties, shrinkage, environmental resistance, temperature tolerance, fire tolerance, color, cost, and volatile evaporation. It is normally the resin, or rather its reactivity, that determines the pulling speed. Typical pulling speeds for polyesters tend to be on the order of 10-20 mm/s, whereas speeds may exceed lOOmm/s under certain circumstances. Apart from the resins characterized in Table 11.2, several other thermosets, such as phenolics, acrylics, and polyurethanes, have been tried, as have several thermoplastics (as will be discussed in Sec. 11.2.6). 

The electrical, mechanical, and thermal properties of the crystal are then largely determined by the electrons in the energy levels within the highest occupied bands. 

TABLE 11.2 Examples of Additives that Modify Mechanical Properties, Electrical Conductivity, and Flame Retardancy... 

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