ELECTRICAL
PROPERTIES
The high electrical resistance and dielectric properties of Wevo resins make them extremely suitable for use in high, but also low and medium voltage applications (e.g. sensors and antennas). Thanks to their high insulating properties and low power dissipation during operation, resins help to increase the performance and safety of electrical components.
Representative products
WEVOPUR PD 4
- Low dielectric constant (approx. 3) over a wide frequency range
- Soft system (Shore A 70)
- Low viscosity during application
- Low water absorption
WEVOPUR 71 / 40 M
- High dielectric strength
- Low water absorption
- High elongation at break
- Low application viscosity
WEVOPOX 2512 / WEVODUR HC 1002
- High dielectric strength
- Low shrinkage
- High Tg
- Thermosetting
Voltage ranges
Relative dielectric constant εr
This temperature and frequency-dependent property indicates the dielectric characteristics and orientation of a polymeric material in an electrical field. The lower the value, the less responsive the insulating material is to the existing field (e.g. in a capacitor). Conversely, this results in better insulation. Particularly in the field of sensor and antenna technology there is a demand for resins that do not display any significant temperature and frequency-dependent changes in the dielectric constant.
Loss factor tan δ
This loss factor describes how much energy absorbed by a polymer in an alternating electrical field is converted into heat. For this reason, encapsulants with a high loss factor are not suitable for use as insulators in high-frequency applications.
Surface resistance
Surface resistance, which is defined as the electrical resistance that impedes or prevents the flow of current between two electrodes of a surface-mounted insulator, is influenced by a number of parameters. Besides the insulating material itself, a decisive role is played by factors such as humidity, the measuring arrangement and surface impurities. The unit of surface resistance and surface resistivity is ohm.
Insulation resistivity
Insulation resistivity describes the resistance of a polymer (or generally speaking, any insulator) to current flowing through it. It is often referred simply as (electrical) resistance and is measured in ohms. The insulation resistivity of many materials is independent of the applied voltage, directly proportional to the length, and inversely proportional to the cross-section of the current-carrying test piece.
Dielectric strength
If the voltage applied to an insulator (polymeric material) exceeds its dielectric strength, the result is a voltage breakdown (electric arc). In case of encapsulants used to insulate an electronic component, dielectric strength describes the electrical breakdown strength for a given voltage range. Thus, polyurethanes are usually used in the low (1–1.5 kV) and medium (1–50 kV) voltage ranges, while epoxies are also used in the high-voltage range (> 50 kV, e.g. power supply).