Tests for Electrical Properties

Any specimen thickness can be used the most common thickness is between 0.8 and 3.2 mm. ] The test specimen is placed between two electrodes in air or oil. To test for the breakdown voltage, voltage is applied across two electrodes and increased from zero until electrical bum-through punctures the sample, or decomposition occurs. ] 

AC Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical Insulation. Primary Film Test Method ASTM D150 Additional Test Method lEC 60250. The ability of an insulator to store electrical energy can be measured through the dielectric constant, which is the ratio of the capacitance induced by two metallic plates with a film sample between them to the capacitance of the same plates with air or a vacuum between them. Better insulating materials have lower dielectric constants. Higher dielectric constants are used when high capacitance is needed. ] 

The dissipation factor measures the inefficiency of an insulating material and is defined as the reciprocal of the ratio between the insulating material s capacitive reactance to its resistance at a specified frequency. ] 

The test method ASTM D150 is performed on a flat sample larger than 50 mm in diameter. The sample is placed between two metallic plates and capacitance is measured. A second test is made without the specimen between the two electrodes. The ratio of these two values is the dielectric constant, 

DC Resistance or Conductance of Insulating Materials. Primary Film Test Method ASTM D257 Additional Test Method lEC 60093. The test method ASTM D257 covers direct-current (DC) procedures for the determination of insulation resistance, volume resistance, volume resistivity, surface resistance, and surface resistivity of electrical insulating materials, or the corresponding conductances and conductivities. 

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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. 

The Underwriters Laboratories (UL) tests are recognized by various industries to provide continuous temperature ratings, particularly in electrical applications. These ratings include separate listings for electrical properties, mechanical properties including impact, and mechanical properties without impact. The temperature index is important if the final product has to receive UL recognition or approval. 

Piezo-electricity is the property, possessed by some crystals, of developing electric charges when compressed or extended in particular directions. Conversely, when a potential difference is applied to suitable points on such a crystal, it expands or contracts. Piezo-electric properties can occur in all crystals lacking a centre of symmetry, except those belonging to the cubic class 432 (Wooster, 1938). A test for such properties, suitable for small crystals or even powders, is the following,... 

Standard test method for rubber property-volume resistivity of electrically conductive and antistatic products Specification for electrical properties of conducting and antistatic products made from flexible polymeric material... 

Electron correlation plays a role in electrical response properties and where nondynamical correlation is important for the potential surface, it is likely to be important for electrical properties. It is also the case that correlation tends to be more important for higher-order derivatives. However, a deficient basis can exaggerate the correlation effect. For small, fight molecules that are covalently bonded and near their equilibrium structure, correlation tends to have an effect of 1 5% on the first derivative properties (electrical moments) [92] and around 5 15% on the second derivative properties (polarizabilities) [93 99]. A still greater correlation effect is possible, if not typical, for third derivative properties (hyperpolarizabilities). Ionic bonding can exhibit a sizable correlation effect on hyperpolarizabilities. For instance, the dipole hyperpolarizability p of LiH at equilibrium is about half its size with the neglect of correlation effects [100]. For the many cases in which dynamical correlation is not significant, the nondynamical correlation effect on properties is fairly well determined with MP2. For example, in five small covalent molecules chosen as a test set, the mean deviation of a elements obtained with MP2 from those obtained with a coupled cluster level of treatment was 2% [101]. 

ASTM Committee D-20 on Plastics has subcommittees working on testing methods for strength, hardness, thermal, optical, and permanence properties, and analytical and molding procedures. Testing methods for electrical properties are under the jurisdiction of Committee D-9 on Electrical Properties. Some methods of immediate interest to those... 

In principle, it should also be possible to add a semi-loced potential to the non-relativistic all-electron Hamiltonian to eirrive at a quasi-rela-tivistic all-electron method. One such suggestion has been made by Delley [76], but the resulting method has only been tested for valence properties, which could also have been obtained by valence-only methods. Effective core potential methods have the advantage of a reduced computational effort (compared to all-electron methods) and are a valuable tool as long as one is aware of the limited domain of valence-only methods. Properties for which density variations in the atomic core are important should not be calculated this way. Examples are the electric field gradient at the nucleus or the nuclear magnetic shielding. 

Molecules that undergo fast random polymerization on the electrode surface, like tetraphenylporphyrins with amino or pyrrole substituents on the phenyl ring, will form films with a well-developed surface but poor catalytic properties for NO oxidation and low electrical conductivity. Out of more than forty different porphyrinic and nonpor-phyrinic and organic and inorganic electrocatalysts tested for these properties, only three show the desired characteristics tetrakis (3-methoxy-4-hydroxyphenyl)... 

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... 

The electrical properties of rubbers may be varied enormously but can be considered to fall into one of three classes, dependent on the resistivity of the end product. Testing for electrical performance of rubber is not entirely consistent and may involve testing of an article or composite, or determination of the fundamental performance characteristics. 

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... 

The electrical properties will also depend on the above factors as well as on the test conditions, in particular temperature, test frequency and humidity. Table 26.12 quotes ranges for figures quoted in the literature for various electrical properties. 

The Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (UL 94) has methods for determining whether a material will extinguish, or burn and propagate flame. The UL Standard for Polymeric Materials-ShortTerm Property Evaluations is a series of small-scale tests used as a basis for comparing the mechanical, electrical, thermal, and resistance-to-ignition characteristics of materials. 

Procedure for conditioning test specimens can call for the following periods in a standard laboratory atmosphere [50 2% relative humidity, 73.4 1.8°F (23 1°C) Adequate air circulation around all specimens must be provided. The reason for this test is due to the fact the temperature and moisture content of plastics affects different properties such as the physical and electrical properties. In order to get comparable test results at different times and in different laboratories a standard has been established. 

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