High-Density PTFE Cable Insulation for Anti-Corona Applications
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Solution Overview
Problem
The introduction of metal oxides into polytetrafluoroethylene (PTFE) to prevent the corona effect is challenging due to increased porosity and low density, which complicates extrusion and leads to a material that is not suitable for high-voltage electrical cables, especially in aeronautical applications where low air pressure exacerbates the issue.
Innovation Solution
A PTFE material with a density greater than 1.45 is developed by incorporating 5-15% metal oxide, 15-30% lubricant, and 0.1-1% wetting agent, along with controlled particle size and specific surface of metal oxide particles, to create a high-density material that effectively dissipates electrons and prevents the corona effect, using a two-stage mixing process and subsequent extrusion, calendering, and drying steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal oxide is introduced into PTFE to prevent corona effect, then anti-corona property is improved, but material density decreases due to increased porosity
Solution Approach 1:
A lubricant is introduced as an intermediary substance during the extrusion process to facilitate the formation of high-density PTFE containing metal oxide. The lubricant enables proper material flow and compaction during extrusion, allowing the metal oxide particles to be properly incorporated without creating excessive porosity, thus maintaining high density while achieving anti-corona properties.
Solution Approach 2:
The invention optimizes the particle size and specific surface area of metal oxide particles as critical parameters. By controlling these parameters, the metal oxide can be effectively incorporated into PTFE to provide anti-corona protection while minimizing the impact on material density and ensuring proper extrusion characteristics.
2Reliability
If metal oxide is introduced into PTFE to prevent corona effect, then anti-corona property is improved, but extrusion process becomes difficult
Solution Approach 1:
The lubricant acts as a mediator during extrusion, reducing friction and enabling smooth flow of the metal oxide-PTFE composite material through the extrusion die. This intermediary substance prevents clogging and breakage issues that would otherwise occur when extruding materials containing metal oxide fillers.
Solution Approach 2:
The invention carefully controls the particle size and specific surface area of metal oxide particles to optimize extrusion characteristics. By adjusting these parameters, the material maintains good flow properties and extrudability while still providing effective anti-corona protection.
3Ease of manufacture
If lubricant is added to improve extrusion, then extrusion process is facilitated, but pores are created during drying reducing density
Solution Approach 1:
The invention optimizes the quantity and type of lubricant used, and controls the drying parameters (temperature, time, atmosphere) to evaporate the lubricant completely without creating pores. By carefully adjusting these parameters, the lubricant serves its function during extrusion then disappears without leaving voids, maintaining high material density.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting material effectively prevents the corona effect, maintains high density, and can be extruded without breaking, making it suitable for high-voltage electrical cables, particularly in aeronautical applications, while also providing thermal resistance and improved miscibility with fillers.
Implementation Method 1
the electrons, subjected to an intense electric field, acquire enough energy to cause the ionization of the neutral molecules (for example, gas molecules constituting the air) and thus create new free electrons, also likely to ionize other neutral molecules. When the voltage is sufficient, an electric arc occurs. This phenomenon, also called corona effect
Implementation Method 2
a material based on polytetrafluoroethylene (PTFE), with a usual density greater than 1.45... an electric cable comprising a strip of material according to the invention, wound around a conductive core
Implementation Method 3
15 to 30% by weight of a lubricant, preferably 20 to 27% by weight... These phenomena can be solved by adding a lubricant to the composition
Implementation Method 4
0.1 to 1% by weight of a wetting agent, preferably 0.3 to 0.7% by weight... the wetting agent allows better miscibility of the PTFE with the fillers
Data Source
AI summary
The present invention relates to a material based on high-density polytetrafluoroethylene (PTFE) and the applications thereof, such as the manufacture of electric cables. The PTFE material according to the invention comprises PTFE, a metal oxide, a lubricant and a wetting agent.