Insulated Wire Coating Composition for Strong Metal-Polymer Adhesion
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Solution Overview
Problem
Insulated wires in electrical devices face poor adhesive force between the conductive wire and the insulating layer due to the weak bonding between metal or alloy conductive wires and thermoplastic resin insulating layers, leading to detachment issues that affect insulation properties and heat resistance.
Innovation Solution
An insulated wire design using a conductive wire coated with an insulating layer composed of thermoplastic polyimide (TPI) and polyetheretherketone (PEEK), where the PEEK content is limited to 20% or less, and the wire is preheated, surface-treated, and extruded at controlled temperatures to form a direct bond without an intermediate layer, reducing bubble formation and enhancing adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an intermediate layer is added between the insulating layer and the conductive wire to increase adhesive force, then the adhesive force between the insulating layer and the conductive wire is improved, but the preparation process becomes complex and time-consuming
Solution Approach 1:
The patent introduces a specific intermediate layer composition (polyetheretherketone and thermoplastic polyimide in specific ratios) that acts as a mediator between the conductive wire and the insulating layer. This intermediate layer provides chemical bonding groups that enhance adhesion to both the metal wire surface and the thermoplastic resin, resolving the adhesion problem without requiring complex multi-step preparation processes. The key is selecting materials with compatible surface energies and chemical properties that facilitate bonding to both substrates.
Solution Approach 2:
The patent optimizes the composition parameters of the intermediate layer by controlling the mass percentage ratios of polyetheretherketone (5-20%) and thermoplastic polyimide (80-95%). By adjusting these compositional parameters, the intermediate layer achieves optimal adhesion properties. Additionally, the surface roughness of the conductive wire is controlled within specific ranges (Ra 0.5-1.6 μm) to enhance mechanical interlocking, thereby improving adhesive force through parameter optimization rather than process complexity.
2Reliability
If the insulating layer uses thermoplastic resin as the main insulating material, then the insulating layer provides good insulation properties, but the adhesive force between the conductive wire and the insulating layer is poor
Solution Approach 1:
The patent creates a composite insulating layer structure consisting of three components: polyetheretherketone (providing adhesion to metal), thermoplastic polyimide (providing insulation and processability), and optional coupling agents. This composite material approach allows each component to fulfill its specific function - the polyetheretherketone ensures strong bonding to the conductive wire, while the thermoplastic polyimide maintains excellent insulation properties and electrical performance, achieving both adhesion and insulation requirements simultaneously.
Solution Approach 2:
The insulating layer is designed with differentiated local properties: the region adjacent to the conductive wire contains higher concentrations of polyetheretherketone and chemical bonding groups optimized for metal adhesion, while the outer region maintains higher thermoplastic polyimide content for optimal insulation and electrical performance. This spatial differentiation of material composition allows the same insulating layer to provide both strong adhesion at the wire interface and excellent insulation at the outer surface.
3Strength
If the conductive wire surface is roughened to improve adhesion, then the adhesive force is improved, but the surface roughness control becomes more difficult
Solution Approach 1:
The patent specifies precise surface roughness parameter ranges (Ra 0.5-1.6 μm) for the conductive wire before applying the insulating layer. This parameter control is achieved through standardized surface treatment processes such as controlled abrasion, plasma treatment, or chemical etching that consistently produce the desired roughness range. The specified range balances adhesion improvement (which increases with roughness) against potential drawbacks like stress concentration and material waste, providing an optimal window that is relatively easy to control in manufacturing.
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 solution provides excellent adhesive force between the insulating layer and conductive wire, improving breakdown voltage and heat resistance, allowing the wire to be used in high-voltage applications up to 260°C without additional bonding layers, thus reducing complexity and cost.
Implementation Method 1
the insulating layer is formed on the surface of the conductive wire through an extrusion process
Implementation Method 2
after extrusion and cooling for 24 h, under a condition that the insulated wire is ring cut (circumferentially cut) and stretched by 15%
Implementation Method 3
surface roughness Ra of the conductive wire is greater than 0.5 and less than 1.6
Data Source
Figure 1~2
Figure 3
AI summary
The present application provides an insulated wire and a preparation method therefor, a winding wire and an electrical device, relating to the technical field of electrochemical elements. The insulated wire includes a conductive wire and an insulating layer coated on the conductive wire, where the insulating layer includes polyetheretherketone and thermoplastic polyimide, and a mass percentage of the polyetheretherketone in the insulating layer is not more than 20%; and the conductive wire is in direct contact with the insulating layer; and after extrusion and cooling for 24 h, under a condition that the insulated wire is ring cut and stretched by 15%, a length of the insulating layer losing adhesion is not greater than 1.9 mm. The present application further provides a preparation method for the above insulated wire and an electrical device using the above insulated wire. The insulated wire provided in the present application overcomes the defect of poor adhesive force between the insulating layer and the conductive wire in the prior art.