Foamed Polyolefin Cable Insulation for Flexibility and Strength
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Solution Overview
Problem
Existing electric cables face challenges in flexibility and mechanical strength during installation due to expanded insulating layers, which can impair insulating properties and lead to premature ageing, and require easy peeling-off capabilities without compromising mechanical integrity.
Innovation Solution
A silane-based cross-linking system combined with an exothermic foaming agent is used to create a properly expanded and cross-linked polyolefin insulating layer, providing improved flexibility, peeling-off ease, and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an expanded insulating layer is used to increase flexibility, then the cable flexibility is improved, but the mechanical strength and insulating properties deteriorate
Solution Approach 1:
The patent uses a composite structure with an inner layer of cross-linked polyolefin foam (expanded material) for flexibility and an outer layer of non-expanded polymeric material for mechanical strength. This composite approach allows the cable to benefit from both expanded and non-expanded material properties, resolving the contradiction between flexibility and mechanical strength.
Solution Approach 2:
The patent applies different expansion degrees to different regions of the insulating coating. The inner layer has a higher expansion degree (50-90%) to provide flexibility, while the outer layer has a lower expansion degree (0-30%) to maintain mechanical strength and insulating properties. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Ease of operation
If an expanded insulating layer is used to increase flexibility, then the cable flexibility is improved, but the insulating properties deteriorate
Solution Approach 1:
The composite structure with an inner expanded layer and an outer non-expanded layer ensures that the insulating properties are maintained by the dense outer layer while the flexible inner layer provides the desired flexibility. The outer layer acts as a protective barrier that preserves electrical insulation.
Solution Approach 2:
By localizing the expansion to the inner layer away from the conductor, the patent maintains high insulating properties in the region where the electrical field is most relevant (near the conductor), while still providing flexibility through the expanded outer regions.
3Ease of operation
If the expansion degree is increased to improve flexibility, then the cable flexibility is improved, but the mechanical integrity deteriorates
Solution Approach 1:
The composite structure distributes the mechanical load between the expanded inner layer and the non-expanded outer layer. The outer layer with lower expansion degree (0-30%) maintains mechanical integrity and protects the more flexible inner layer, resolving the contradiction between flexibility and mechanical integrity.
4Quantity of substance
If chemical foaming agents are used to produce cross-linked polyolefin foam, then the expansion is achieved, but the process control becomes difficult
Solution Approach 1:
The patent carefully controls the amount of foaming agent (0.1% to 0.5% by weight) and uses a silane-based cross-linking system with specific temperature conditions to achieve controlled expansion. By optimizing these parameters, the patent achieves reliable expansion while maintaining good process control, avoiding the difficulties associated with conventional chemical foaming.
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 enhances the ageing stability and mechanical properties of the cable while maintaining flexibility and ease of peeling-off, addressing the limitations of previous technologies.
Implementation Method 1
a silane-based cross-linking system combined with an exothermic foaming agent is used to create a properly expanded and cross-linked polyolefin insulating layer
Implementation Method 2
exothermic foaming agent is used to create a properly expanded and cross-linked polyolefin insulating layer
Implementation Method 3
cross-linked polyolefin foam is produced by using chemical foaming agents, such as azodicarbonamide, which decompose on being heated and generate gaseous nitrogen
Data Source
AI summary
A process for manufacturing an electric cable including at least one core including a conductor and an insulating coating surrounding the conductor includes the steps of: providing a polyolefin material, a silane-based cross-linking system and a foaming system including at least one exothermic foaming agent in an amount of 0.1% to 0.5% by weight with respect to the total weight of the polyolefin material; forming a blend with the polyolefin material, the silane-based cross-linking system and the foaming system; and extruding the blend on the conductor to form the insulating coating. An electric cable includes at least one core consisting of a conductor and an insulating coating surrounding the conductor and in contact therewith, the insulating coating consisting of a layer of expanded, silane-cross-linked polyolefin material having an expansion degree of 3% to 40%.