Dielectric performance properties

The combination of thermal stability and dielectric performance makes PEN an attractive electrical insulator in electrical motors. Motors with high operating temperatures, such as hermetically sealed refrigerator motors and business machines, need films that are resistant to shrinking and retain nonconducting properties at high temperatures. 

The electrical properties of the polylmldes Investigated are all consistent with good Interlevel dielectric performance. The room temperature I-V characteristic Indicates non-llnearlty of current density with field or square root of field. At typical field use conditions of 5 x 10 V/cm, polylmlde conductivity Is A-10 which Is similar to that of thermal SIO2. At higher fields such as 2 x 10 V/cm, conductivity of polylmlde Increases... 

Next to the printing process, also materials for printed electronics have to be carefully engineered. Materials for printed electronics can be subdivided into conductors, semiconductors and dielectrics. However, it is important not to look at the single materials, but to combinations of materials with matching properties. An optimized transistor for instance has electrodes of a conductor plus a dielectric with properties that match those of the semiconductor, resulting in optimal device performance. Evonik aims to supply such system solutions for the printed electronics market. 

Laboratory-on-a-chip systems use immittance and dielectric variables measured with microelectrodes. In flow sensors, cell properties are measured with microelectrodes, and cell characterization and cell separation are performed. Properties of protein molecules have, for many years, been determined by the established methods of electrophoresis. Electrophoresis is based on the electric charge of cells and proteins, and the driving force exerted by an electric field. AU sorts of liquid suspensions with cells or bacteria can be measured with bioimmittance or permittivity. Cell adherence and cell micromotion can be monitored with microelectrodes equipped with a thin surface coating. 

Table 10.8 shows electric strengths. Table 10.9 shows volume resistivities, Table 10.10 shows dielectric constants, and Table 10.11 shows dissipation factors for coatings using most of the available resins. Magnet wire insulation is an important use for organic coatings. National Electrical Manufacturer s Association (NEMA) standards and manufacturers trade names for various wire enamels are shown in Table 10.12. This information can be used to guide the selection of coatings. However, it is important to remember the aforementioned warnings about blends of various resins and the effects on performance properties.

On the other part, the incorporation of bulky aromatic phosphorus pendant group into PSF s side chain influenced their reologi-cal properties. The maximum hydrophobicity of the polysulfones with bulky phosphorus jiendant groups, in which the work of water adhesion is very low comparatively with the work of cohesion, correlated with low adhesion to interfaces, would be advantageous for dielectric performance in different biological applications. Atomic force microscopy showed that the increase of density of the bulky phosphorus pendant groups determine the formation of domains... 

There are other transitions in molecular conformations that give rise to loss peaks in oscillatory experiments such as the torsion pendulum. Often the modulus changes by such a small amount at a minor transition that performance properties are not noticeably affected. It has been pointed out that an additional amorphous change occurs well below the main glass transition temperature of poly(tetrafiuoroethylene) (Figure 9.16). In the dielectric relaxation literature... 

The presence of surface conductance behind the slip plane alters the relationships between the various electrokinetic phenomena [83, 84] further complications arise in solvent mixtures [85]. Surface conductance can have a profound effect on the streaming current and electrophoretic mobility of polymer latices [86, 87]. In order to obtain an accurate interpretation of the electrostatic properties of a suspension, one must perform more than one type of electrokinetic experiment. One novel approach is to measure electrophoretic mobility and dielectric spectroscopy in a single instrument [88]. 

A combination of excellent chemical and mechanical properties at elevated temperatures results in rehable, high performance service to the chemical processing and related industries. Chemical inertness, heat resistance, toughness and flexibiUty, stress-crack resistance, excellent flex life, antistick characteristics, Htfle moisture absorption, nonflammability, and exceptional dielectric properties are among the characteristics of these resins. 

Another important use of dielectrics is as intermetal dielectrics (IMDs), where the dielectrics insulate metal lines from each other. The dielectric material must fill small gaps with high aspect ratios (depth to width) while maintaining all other dielectric properties. It is essential that the IMDs are void-free at submicrometer dimensions for both performance and rehabiUty. 

Semiconductors (qv) are materials with resistivities between those of conductors and those of insulators (between 10 and 10 H-cm). The electrical properties of a semiconductor determine the hmctional performance of the device. Important electrical properties of semiconductors are resistivity and dielectric constant. The resistivity of a semiconductor can be varied by introducing small amounts of material impurities or dopants. Through proper material doping, electron movement can be precisely controlled, producing hmctions such as rectification, switching, detection, and modulation. 

Electrical Properties. Polysulfones offer excellent electrical insulative capabiUties and other electrical properties as can be seen from the data in Table 7. The resins exhibit low dielectric constants and dissipation factors even in the GH2 (microwave) frequency range. This performance is retained over a wide temperature range and has permitted appHcations such as printed wiring board substrates, electronic connectors, lighting sockets, business machine components, and automotive fuse housings, to name a few. The desirable electrical properties along with the inherent flame retardancy of polysulfones make these polymers prime candidates in many high temperature electrical and electronic appHcations. 

The main electroceramic apphcations of titanium dioxide derive from its high dielectric constant (see Table 6). Rutile itself can be used as a dielectric iu multilayer capacitors, but it is much more common to use Ti02 for the manufacture of alkaline-earth titanates, eg, by the cocalciuation of barium carbonate and anatase. The electrical properties of these dielectrics are extremely sensitive to the presence of small (<20 ppm) quantities of impurities, and high performance titanates require consistently pure (eg, >99.9%) Ti02- Typical products are made by the hydrolysis of high purity titanium tetrachloride. 

The exceUent adhesion to primed films of polyester combined with good dielectric properties and good surface properties makes the vinyhdene chloride copolymers very suitable as binders for iron oxide pigmented coatings for magnetic tapes (168—170). They perform very weU in audio, video, and computer tapes. 

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