ASTM D257 test methods determine the volume resistance, insulation resistance, and surface resistance of insulating materials through direct current procedures. ASTM D257 test methods are not suitable for use in measuring the electrical resistance/conductance of moderately conductive materials. In addition, volume resistivity or conductivity can also be calculated from resistance and dimensional data of the specimen. Read more about ASTM D257 DC Resistance or Conductance of Insulating Materials below.
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Introduction to ASTM D257
ASTM D257 provides standard test methods to measure the conductance, conductivity, volume, and surface resistivity of electrical insulating materials. Electrically insulating materials isolate components of an electrical system from each other and from ground, and also provide mechanical support for the components. High insulation resistance, consistent with acceptable mechanical, chemical, and heat-resisting properties, is always desirable. The mechanical, chemical and heat-resisting properties of the specimen are determined through ASTM D257 test method. The results obtained are specially used for quality control and specification purposes. ASTM D257 test methods cover direct-current procedures for the measurement of dc insulation resistance, volume resistance, and surface resistance. In ASTM D257 test method, a standard size specimen is placed between two electrodes. A voltage is applied for sixty seconds and the resistance is measured. Surface or volume resistivity is calculated, and apparent value is given (60 seconds electrification time); the higher the surface/volume resistivity, the lower the leakage current and the less conductive is the material.
ASTM D257 test method is generally applicable to insulating materials but not suitable for use in measuring electrical resistance and conductance of moderately conductive materials. The method also provides information about the voltage stress limits, electrode geometry, precision of specimen configuration, and finite electrification. MaTestLab has the best network of testing labs in the USA to carry out ASTM D257 test for our clients.
ASTM D257 Test Method
This test method proceeds with the placement of the specimen between the measuring electrodes whose surface is cleaned with a suitable solvent. The surface resistance is then calculated and the details of surface cleaning are recorded. The method covers the determination of the resistance and conductance of the specimen or capacitor by measuring current or voltage drop under specified conditions. The surface and volume resistance or conductance is measured separately by means of appropriate electrode systems. The knowledge of the specimen and electrode dimensions aids in the calculation of resistivity or conductivity.
ASTM D257 Tester
Insulation Resistance or conductance
The specimen is placed in the test chamber and the measurements of conductivity and resistivity are made with a proper device having the required sensitivity and accuracy. The time for electrification is specified as 60 seconds and the applied voltage of 500 V is used.
Surface resistance or conductance
The dimensions and distance between the electrodes are determined along with the surface resistance and conductance between electrodes. The time for electrification is specified as 60 seconds and the direct voltage of 500 V is applied.
ASTM D257 Specimens
Specimen details
ASTM D257 Specimens are flat plates, rods, tapes, and tubes.
Specimen dimensions
The general sample size for ASTM is 20 mm.
Specimen preparation
Specimens are injection molded or cut from molded or extruded sheets or plates.
ASTM D257 Results
This test method provides information about the dielectric breakdown, dissipation factor properties, moisture content, the degree of cure, mechanical continuity, and electric field intensity. The volume and the surface resistivity and conductivity are recorded. The resistance and conductivity values vary with temperature and humidity.
Tests related to ASTM D257 IEC 60093 is similar to ASTM D257. As per IEC 60093, volume resistance is defined as the resistance to leakage current through the body of insulating material. It determines the volume resistivity in correspondence to the direct-current resistance between opposite faces of a meter cube of the material. Surface resistivity is defined as the resistivity to leakage current along the surface of an insulating material. IEC 60093 determines the surface resistivity as the quotient of potential gradient and the current per unit of electrode length. The surface resistivity is reported in ohms.
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Please contact us for a detailed quote for your astm d257 testing needs. Cost incurred to carry out different astm d257 testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
How many samples are required for astm d257?
The required number of samples or specimens should comply with the procedure given in the astm d257 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
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How many days will it take to complete the astm d257 test?
The turnaround time for astm d257 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
Where can I get the astm d257 tested?
You can share your astm d257 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d257 test to various testing techniques.
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