Testing of electrical properties

Some brief notes on the testing of electrical properties are given in the appendix at the end of this chapter. 

Standard testing of electrical properties of plastics includes dielectric strength, permittivity, dissipation factor, smface and volume resistivity, and arc resistance. Dielectric strength is the maximmn voltage required for breakdown and is determined by one of three techniques short-time, slow-rate or slow-rise, and step-by-step. The two last techniques use data from the short-time test to... 

Within the framework of type verifications for and testing of electrical apparatus in general, technical tests shall furnish proof of mechanical, thermal or electrical properties as specified in the relevant standards. Some examples for type tests are given in the following ... 

Hexamethylcyclotrisilazane and hexamethylcyclotrisiloxane were purified by rectification in vacuum following which their purity was tested by gas chromatography. Plasma polymerizations were carried out in an electrode system described previously ( ). Thin film were deposited in a 20 kHz glow discharge on the surface of stainless steel electrodes or on gold or silicon electrodes in the case of thin layers intended for further studies of electrical properties. All polymerizations were carried out at constant discharge parameters current density j = 1 mA/cm2, discharge duration t = 30 sec, monomer vapour pressure p = 0.3 Torr. 

Table V Indicates the good retention of electrical properties exhibited by the 40% glass-filled PPS at temperatures up to 147°C. In addition, exposure of test specimens to 50 per cent relative humidity for 5 days did not cause any appreciable change In either dielectric constant or dissipation factor. Thus, environmental factors do not have much effect upon the electrical behavior of polyphenylene sulfide resins.

Small nitrile-rubber inclusions in epoxy resin electrical en-capsulants have been examined in both amine (29-31) and acid (32) epoxy cures, in filled and unfilled systems. The value of rubber inclusion in a boron trlfluorlde/amine complex epoxy cure has also been demonstrated (33), where elevated-temperature, high-humldlty testing showed electrical properties retention to be better than a comparable system cured with dodecenylsucclnic anhydride. Rubber benefits low-temperature properties specifically and thermocycling in general. It affects high temperature insulation properties negatively therefore, the amount of rubber incorporated must be judiciously chosen. 

Test (he electrical properties (resistivity and or permittivity) of the immersion liquid to be used. Contamination of the liquid can often lead to erroneously high breakdown voltage values. 

Electrical properties of grain have been utilized for quick moisture tests based on the measurement of resistance, capacitance, or electrical conductivity. Many studies have been devoted to the development of density-independent functions of the dielectric properties that would permit on-line measurement of moisture content [74-76]. Also, measurements of electrical properties of grain and seed have been employed for purposes other than determining moisture content. For example, viable seeds of corn were sorted from dead seeds by measuring the current conducted by individual soaked kernels between electrodes connected to a 6-V dc source [77]. Another application of electrical properties is electrostatic separation where the ability of a seed to hold a surface charge is determined mainly by its conductivity. 

BS 2782 Part 2 Methods of Testing Plastics - electrical properties BS 2782 ... 

Electrical Resistance—Conductivity. Most fillers are composed of nonconducting substances that should, therefore, provide electrical resistance properties comparable to the plastics in which they are used. However, some fillers contain adsorbed water or other conductive species that can gready reduce their electrical resistance. Standard tests for electrical resistance of filled plastics include dielectric strength, dielectric constant, arc resistance, and d-c resistance. 

Testing. Various test methods are provided by ASTM (16). These iaclude pigment tests of importance such as chemical analysis, presence of oversize particles, oil absorption, particle size distribution, degree of dispersion, presence of soluble components, etc. Numerous tests are also given by ASTM for the properties of filled and unfilled polymers. These iaclude, for example, such properties as impact resistance, stiffness, viscosity, tear resistance, hardness, color, and electrical resistivity. 

Electrical Properties. Electrical properties are important for the corrosion protection of chip-on-board (COB) encapsulated devices. Accelerated temperature, humidity, and bias (THB) are usually used to test the embedding materials. Conventional accelerating testing is done at 85°C, 85% relative humidity, and d-c bias voltage. Triple-track test devices with tantalum nitride (Ta2N), titanium—palladium—gold (Ti—Pd—Au) metallizations with 76... 

Since the incorporation of plasticisers into a polymer compound brings about a reduction in glass temperature they will also have an effect on the electrical properties. Plasticised PVC with a glass temperature below that of the testing temperature will have a much higher dielectric constant than unplasticised PVC at the same temperature (Figure 6.6). 

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