Porous Polyimide Insulating Layer for Cable Crack Resistance
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Solution Overview
Problem
Conventional insulated electrical cables with polyimide insulating layers face challenges in high-temperature and high-humidity environments, where hydrolysis leads to reduced film strength and potential cracking, and the existing methods to suppress cracking are complex and require multiple layers, compromising flexibility.
Innovation Solution
An insulated electrical cable with a polyimide-based insulating layer having a porosity of 25% to 60% by volume, incorporating pores to disperse stress and enhance flexibility, along with a primer layer for improved adhesion and mechanical properties, and using a condensation polymer of aromatic tetracarboxylic dianhydride and diamine for enhanced heat resistance and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a polyimide insulating layer is used for excellent heat resistance, then heat resistance is improved, but film strength is lowered due to hydrolysis in high-temperature high-humidity environments leading to cracking
Solution Approach 1:
The insulating layer is designed with a porous structure containing numerous pores with an average diameter of 1 μm to 10 μm. This porous configuration reduces the density of the polyimide material, thereby minimizing the overall amount of material susceptible to hydrolysis while preserving the insulating properties. The pores act as stress relief zones that prevent crack propagation, allowing the cable to maintain film strength even when used in high-temperature high-humidity environments where polyimide degradation would normally occur
2Reliability
If multiple layers are formed to suppress cracking, then crack resistance is improved, but the manufacturing process becomes extremely complicated
Solution Approach 1:
The insulating layer is segmented into a porous structure with numerous distributed pores throughout the material. This segmentation creates multiple small compartments that isolate stress concentrations and prevent crack propagation across the entire layer. Instead of applying multiple separate coating layers, the segmentation is achieved within a single polyimide layer through controlled pore formation, thereby maintaining crack resistance while avoiding the complexity of multi-layer manufacturing processes
3Strength
If a dense insulating layer is used, then film strength is maintained, but flexibility is reduced
Solution Approach 1:
The insulating layer employs a porous structure with controlled pore distribution that creates a more compliant material architecture. The pores act as cushioning elements that allow the material to deform more easily under bending stresses, thereby improving flexibility. Simultaneously, the porous polyimide maintains sufficient film strength through the distributed pore structure that prevents stress concentration, resolving the trade-off between strength and flexibility
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 cable effectively suppresses cracking and maintains excellent flexibility, even under high-temperature and high-humidity conditions, while simplifying the manufacturing process by reducing the need for multiple layers and enhancing mechanical properties.
Implementation Method 1
the insulating layer includes a plurality of pores, and a porosity of the insulating layer is greater than or equal to 25% by volume and less than or equal to 60% by volume... it is considered to be able to disperse and reduce stress generated by processing
Implementation Method 2
the film is deteriorated by hydrolysis of the polyimide and the film strength is lowered
Data Source
AI summary
An insulated electrical cable includes: a conductor; and an insulating layer that is laminated on an outer peripheral surface of the conductor and includes a polyimide as a main component, wherein the insulating layer includes a plurality of pores, and wherein a porosity of the insulating layer is greater than or equal to 25% by volume and less than or equal to 60% by volume.