PTFE Thorium Oxide Membrane Sintering for Anti-Corona Insulation
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Solution Overview
Problem
Existing methods face challenges in incorporating metal oxides like titanium dioxide into polytetrafluoroethylene (PTFE) to prevent the corona effect in electric cables, leading to increased porosity, low density, and complications in the extrusion process, while maintaining insulation and integrity.
Innovation Solution
A method involving the combination of thorium oxide with PTFE resin, lubricant, and wetting agent, followed by controlled sintering and cooling to form a homogeneous membrane, ensuring encapsulation and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal oxide fillers are introduced into extruded PTFE to achieve anti-corona effect, then electrical insulation properties are improved, but porosity increases and density decreases
Solution Approach 1:
The patent changes the physical-chemical parameters of the PTFE material by introducing metal oxide fillers (titanium dioxide, thorium oxide) at specific concentrations (20-40 wt%). This modification alters the electrical properties to achieve anti-corona effect while managing the resulting porosity and density changes through controlled formulation
Solution Approach 2:
The patent creates composite materials by combining PTFE with metal oxide fillers. The composite structure integrates the electrical insulation properties of PTFE with the anti-corona characteristics of metal oxides, achieving enhanced electrical performance despite the inherent porosity increase from filler incorporation
2Reliability
If metal oxide fillers are introduced into extruded PTFE to achieve anti-corona effect, then electrical insulation properties are improved, but extrusion process becomes complicated
Solution Approach 1:
The patent modifies the extrusion process parameters to accommodate metal oxide fillers, including adjusting temperature profiles, pressure conditions, and screw speeds. These parameter changes enable successful processing of filler-containing compounds while maintaining product quality
Solution Approach 2:
The patent uses lubricants and processing aids as intermediaries to facilitate the extrusion of filler-containing PTFE. These additives reduce friction and improve flow characteristics, enabling the extrusion process to handle the higher viscosity and friction caused by metal oxide fillers
3Ease of manufacture
If lubricant is added to the composition to aid extrusion, then ease of manufacture is improved, but pores are created during drying phase
Solution Approach 1:
The patent optimizes the lubricant concentration and drying parameters to minimize pore formation. By carefully controlling the balance between lubricant content (for extrusion ease) and drying conditions (to prevent excessive porosity), the patent achieves acceptable compromise in the final material density
Solution Approach 2:
The patent applies lubricants selectively in the extrusion zone where they are most needed for processability, while minimizing their presence in the final dried product. This localized application ensures ease of manufacture during processing while reducing the negative impact on final 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 method produces a PTFE thorium oxide membrane with enhanced insulation, thermal stability, and mechanical strength, effectively mitigating the corona effect and maintaining material integrity.
Implementation Method 1
The sintering involves heating above the crystalline melting point of polytetrafluoroethylene (PTFE) but below the melting point of thorium oxide
Implementation Method 2
cooling the sintered tape at a controlled rate to prevent crack formation and maintain the integrity of the membrane structure
Data Source
AI summary
The present disclosure relates to a method 200 for producing polytetrafluoroethylene (PTFE) thorium oxide membrane. The method 200 comprising combining metal oxide and polytetrafluoroethylene (PTFE) powder to form a first mixture and screening the first mixture to remove aggregates. The method 200 also comprising mixing a lubricant, wetting agent, and optional pigments to form a second mixture and spraying the second mixture over the first mixture. The method 200 also comprising compacting the homogeneous product into a preform and extruding and calendaring the preform to obtain a tape of desired thickness. The method 200 also comprising heating the tape formed to evaporate the lubricant and sintering the tape to fuse polytetrafluoroethylene (PTFE) and encapsulate the thorium oxide particles. The method 200 also comprising cooling the sintered tape at a controlled rate to prevent crack formation and maintain the integrity of the membrane structure.