Insulated Wire Diameter Reduction via Semiconductive Layer Segmentation
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Solution Overview
Problem
Existing insulated wires face challenges in reducing their outer diameter while maintaining high levels of insulation and flame-retardant properties, as the flame-retardant layer's low volume resistivity and poor adhesion to the resin lead to moisture infiltration and reduced direct-current stability.
Innovation Solution
The introduction of a flame-retardant semiconductive layer with a volume resistivity of ≤5.0×10^15 Ωcm and an oxygen index >40, combined with an insulating layer and a flame-retardant layer, forms a three-layer structure that enhances direct-current stability and flame-retardant properties, allowing for diameter reduction without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the flame-retardant layer and insulating layer is reduced to decrease wire diameter, then the weight and outer diameter are reduced, but the direct-current stability deteriorates due to moisture infiltration caused by low volume resistivity and poor adhesion
Solution Approach 1:
The coating layer is divided into three distinct layers: flame-retardant semiconductive layer, insulating layer, and flame-retardant layer. Each layer performs a specific function - the semiconductive layer provides high volume resistivity to prevent moisture infiltration, the insulating layer provides electrical insulation, and the flame-retardant layer provides flame resistance. This segmentation allows optimization of each layer's thickness and properties independently, enabling diameter reduction while maintaining direct-current stability.
Solution Approach 2:
The flame-retardant semiconductive layer uses a composite material containing conductive filler (such as carbon black) dispersed in a flame-retardant resin matrix. This composite provides both high volume resistivity (≥1.0×10^16 Ωcm) and flame-retardant properties (oxygen index ≥40), preventing moisture infiltration while maintaining thin thickness. The combination of conductive filler and flame-retardant resin creates a material that simultaneously achieves electrical stability and flame resistance.
2Length of stationary object
If the thickness of the flame-retardant layer is reduced to decrease wire diameter, then the outer diameter is reduced, but the flame-retardant property deteriorates
Solution Approach 1:
The flame-retardant function is segmented between two layers: the flame-retardant semiconductive layer (providing oxygen index ≥40) and the flame-retardant layer (providing additional flame protection). This segmentation allows the outer flame-retardant layer to be thinner while the overall flame-retardant property is maintained through the combined effect of both layers, each contributing to fire resistance.
Solution Approach 2:
The flame-retardant layer uses composite materials containing flame-retardant fillers (such as metal hydroxides, phosphorus compounds, or nitrogen compounds) dispersed in a resin matrix. These composite materials provide high flame-retardant performance (oxygen index ≥40) at reduced thickness, enabling diameter reduction while maintaining fire safety.
3Reliability
If the volume resistivity of the flame-retardant layer is increased to improve direct-current stability, then the adhesion to resin deteriorates due to the nature of flame-retardant materials
Solution Approach 1:
The adhesion function is assigned to the insulating layer, which is positioned between the flame-retardant semiconductive layer and the flame-retardant layer. The insulating layer uses resin materials with good adhesion properties to ensure strong bonding between layers. This segmentation allows the flame-retardant semiconductive layer to focus on providing high volume resistivity without compromising adhesion, as the insulating layer handles the adhesion requirement.
Solution Approach 2:
The insulating layer acts as an intermediary between the flame-retardant semiconductive layer and the flame-retardant layer. It provides strong adhesion to both layers while maintaining electrical insulation. The insulating layer's resin materials are selected for their excellent adhesion properties, mediating the bond between layers with different material characteristics and ensuring overall coating integrity.
Data Source
AI summary
An insulated wire having an electrical wire structure capable of reducing a diameter while a direct-current stability property and a flame-retardant property are highly kept is provided. In the insulated wire including: a conductor; a flame-retardant semiconductive layer arranged on an outer periphery of the conductor; an insulating layer arranged on an outer periphery of the flame-retardant semiconductive layer; and a flame-retardant layer arranged on an outer periphery of the insulating layer, an oxygen index of the flame-retardant semiconductive layer defined by JIS K7201-2 is larger than 40, and a volume resistivity of the flame-retardant semiconductive layer defined by JIS C2151 is equal to or smaller than 5.0×1015 (Ωcm).