Views: 110 Author: Site Editor Publish Time: 2021-07-19 Origin: Site
Expanded tetrafluoroethylene (ePTFE) is polytetrafluoroethylene that has been expanded or stretched. It has the airtightness of polytetrafluoroethylene and improves the cold flow of polytetrafluoroethylene. Cold fluidity refers to the plastic deformation of material products under long-term continuous load. ePTFE gives it excellent longitudinal and lateral stability, while minimizing the cold deformation and compression creep of the material. It is especially suitable for large pressure vessels, tubular heat exchangers with large diameters and uneven surfaces, large plate heat exchangers, and large glass-lined reactors. Compared with PTFE, ePTFE membrane film is soft and light.
Due to the versatility of ePTFE as a sealing, filtering, vibration damping and corrosion protection material, it is not surprising to know that its electrical characteristics have opened the door to the cable industry.
ePTFE is a variation of pure PTFE or solid PTFE. Its processing method is to inject air into solid PTFE to make it have a sponge-like and malleable texture. Its properties make it the material of choice for sealing applications. A material composed of 70% air helps to greatly increase electrical conductivity and dielectric strength.
The characteristics of pure PTFE membrane make it an excellent insulator in electrical applications. The invention of ePTFE made the material ten times lighter. The dielectric constant is almost halved from 2.1 to 1.3.
Many high-performance cables use solid PTFE membranes, mainly by pasting a PTFE tube onto the conductive core. But wrapping the core in ePTFE provides more wiring possibilities.
The thickness of ePTFE insulating tape can be strictly controlled within 0.05mm. ePTFE insulation has uniform density and dielectric constant. Wrapping a single conductor with ePTFE helps to reduce interference, noise, crosstalk and signal attenuation. In some applications, high-quality ePTFE tape can limit the phase shift to 4.3° and the signal attenuation to 0.05 dB at 110 GHz.
The high dielectric constant ePTFE insulating layer is 50% thinner than other materials.
At higher voltages, corona discharge has to become our concern. After modification of PTFE, it has good performance in carrying wires of 5 kV and higher voltage. Corona resistant PTFE eliminates the tiny gaps between conductors and insulators. These gaps may be the starting location of the corona discharge, so this must attract our attention, especially in high altitude and space applications.
The farthest shield from the neutral axis of the cable means the greatest bending stress. Reducing the friction between the shielding layer and the conductor and the friction between the shielding layer and the sheath can prevent heat generation and maintain the stress of the shielding layer.
Placing the ePTFE adhesive on both sides of the shield allows each conductor to easily slide past its neighbors and the outer shield. This makes the cable as a whole more flexible in terms of rotation and torque, and eliminates internal wear and extends the service life of the cable.
The cable sheath should have additional tensile and flexural strength. The main characteristics of the sheath layer are thinness, tear resistance, fluid erosion resistance and high tensile strength. The durable polyurethane (PU) jacket can be made of ePTFE. If the cable assembly slides over other machine parts, wear-resistant ePTFE is ideal for extending the life of the cable.
ePTFE allows a uniform thickness of tape with a running time of more than 1000 meters. The tapes suitable for cable manufacturing mainly include expanded ptfe sealing tape, customized ePTFE sealing tape and chemical resistant tape.