Because some materials require special handling, ASTM standards or the test method directly applicable to the material being tested should also be consulted. ASTM D149 Standard Test Method for Dielectric Strength and Breakdown Voltage of Solid Electrical Insulating Materials at Commercial Power Frequencies applies to determining the dielectric strength of electrical insulating materials at commercial power frequencies.
The test method described in ASTM D3755 is similar to IEC 243-2. All procedures in this test method are included in IEC 243-2.
This test method is intended for use as a control and acceptance test for direct voltage applications. It can also be used to partially evaluate materials for specific end uses and as a means of detecting changes in materials due to specific deterioration causes.
Experience shows that the fault value obtained with direct voltage is generally about 2 to 4 times the RMS value of the 60 Hz alternating voltage fault.
For an inhomogeneous test specimen, the voltage stress distribution within the specimen is determined by the impedance (largely capacitive) with alternating voltage. With increasing direct voltage, the voltage distribution will still be largely capacitive, but this depends in part on the rate of voltage increase. After the application of a constant direct voltage, the voltage distribution across the specimen is determined by the resistance. The choice of direct or alternating voltage depends on the purpose for which the failure test will be performed and, to some extent, the intended application of the material.
During testing, a sample held in a suitably designed electrode system is electrically stressed by applying an increasing direct voltage until internal breakdown occurs. The test voltage is applied at a uniform rate of increase. The direct voltage is obtained from a high-voltage source with adequate current capacity and regulation, reasonably free of ripple, and facilities for measuring and controlling the output voltage.
Material test specimens are defined and prepared using ASTM methods applicable to the materials to be tested. Specimens representative of the material to be tested must be provided. Enough specimens are prepared to allow five tests. When preparing test specimens from solid materials, the surfaces in contact with the electrodes should be parallel and as flat and smooth as the material allows.
When testing thin solid materials (sheets and plates thinner than 3 mm), test specimens with sufficient space should be prepared to prevent overflow under test conditions.
When testing thick solid materials, the sample should be immersed in the insulating liquid to prevent overflow and minimize partial discharge (the fragmentation of thick solid materials is generally high). Other techniques that can be used to prevent overflow include:
The thickness used in calculating dielectric strength should be the average thickness of the measured sample specified in the test method for the material in question. If not specified, the thickness measurement should be made at room temperature, 25°C plus/minus 5°C. If the material is laminar, or if the dielectric strength is known to vary with orientation due to factors such as grain size, the sample should be cut so that its thickness is directed toward the electric field under operating conditions. If thin materials, such as laminates, are to be tested in their width or length direction, special procedures may be needed to prevent scattering. Provisions for such tests may also be included in the methods for specific materials.
Unless otherwise stated, five samples should be tested.
In short, ASTM D3755 is a standard that covers the requirements for high-temperature thermoplastic elastomers used in industrial and commercial applications. This standard applies specifically to elastomers that must maintain their physical properties and performance in high-temperature environments. The primary objective of this standard is to provide a uniform set of properties for thermoplastic elastomers that can withstand prolonged exposure to temperatures typically ranging from 150°C to 200°C or higher. These materials are commonly used in automotive, electrical, aerospace, and industrial applications where thermal stability, mechanical integrity, and chemical resistance are important.
The ASTM D3755 standard outlines the minimum property requirements that high-temperature thermoplastic elastomers must meet. These typically include:
These properties help the material maintain its dimensional stability, flexibility and strength even under thermal stress.
The ASTM D3755 standard includes different classes of thermoplastic elastomers generally based on:
Each grade is suitable for specific use cases depending on the application environment, such as continuous heat exposure, intermittent stress, or contact with oils or chemicals.
Common areas of application of the ASTM D3755 standard include:
By adhering to this standard, manufacturers can be confident that their products meet stringent safety, performance, and durability requirements in harsh environments. In short, this standard provides a clear framework for material classification and testing, ensuring reliability and consistency across a variety of industries.
Our organization, which has been supporting businesses across all sectors for years with a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with ASTM D3755, Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials Under Direct Voltage Stress.
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