Polypropylene Cable Insulation via Electron Beam Crosslinking
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Solution Overview
Problem
Current polymer insulation materials for cables face challenges in being cost-effective, reprocessable, and maintaining excellent flame resistance while minimizing the negative impact of high mineral filler loads on mechanical and electrical properties.
Innovation Solution
A method involving the mixing of polypropylene resin and polyolefin copolymer rubber at elevated temperatures, followed by the addition of a high loading of mineral filler material, and treatment with high-energy electrons to induce graft-links and cross-linking, allowing for efficient and cost-effective production of a reprocessable insulation material with enhanced mechanical and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If crosslinking is performed on polymers like PE, EPDM and EVA to improve flame resistance, then flame resistance is improved, but reprocessability is lost
Solution Approach 1:
The patent applies preliminary action by incorporating crosslinking agents and initiators into the polymer compound during compounding, but the actual crosslinking reaction is delayed until after extrusion and curing. This allows the material to be processed as a thermoplastic first, then crosslinked later to achieve flame resistance while maintaining reprocessability of the uncrosslinked compound.
2Object-affected harmful factors
If high loading of mineral filler material is added to improve flame resistance, then flame resistance is improved, but mechanical and electrical properties deteriorate
Solution Approach 1:
The patent uses silane-modified polymers as intermediaries between the mineral filler and the base polymer. The silane groups on the polymer chain interact with the mineral filler particles, improving dispersion and adhesion. This intermediary structure allows high filler loading while maintaining mechanical integrity and electrical properties.
Solution Approach 2:
The patent creates a composite material system combining silane-modified polymers with mineral fillers. The composite structure leverages the flame resistance of the mineral filler while the silane-modified polymer matrix maintains mechanical and electrical properties through improved interfacial adhesion and dispersion.
3Productivity
If conventional crosslinking techniques like peroxide crosslinking are used to improve flame resistance, then crosslinking efficiency is improved, but discoloration occurs due to acetophenone generation
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by using silane-based crosslinking instead of peroxide crosslinking. The silane crosslinking mechanism proceeds through different reaction pathways that do not generate discoloring byproducts like acetophenone, while still achieving effective crosslinking. The curing conditions (temperature, time, catalyst) are optimized to control the crosslinking rate and final network structure.
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 resulting insulation material exhibits improved mechanical and electrical properties, oil resistance, thermal stability, flame resistance, and weathering resistance, while being cost-effective and capable of reprocessing, with no need for additional cross-linking agents, thus ensuring long-term stability and efficient production.
Implementation Method 1
treatment with high-energy electrons to induce graft-links and cross-linking
Implementation Method 2
induce graft-links and cross-linking
Implementation Method 3
The mixing takes place at a temperature at which the polymers are in the molten state
Data Source
AI summary
The present invention relates to a method for preparing an insulation material for cables involving three steps. In a first step 15 to 40% by weight of at least one polypropylene rubber, and 15 to 40% by weight of at least one polyolefin copolymer rubber, are mixed together at a temperature being between 5 and 30 °C above the melting temperature of the polymer in the composition having the highest melting temperature. In a second step 40 to 70% by weight of a mineral filler material are added to the mixture obtained in the first step and the obtained composition is homogenized. In a third step the compositing obtained in the second step is treated with high energy electrons while mixing.