Crosslinkable Polyethylene Peroxide Migration Reduction
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Solution Overview
Problem
Current crosslinkable polyethylene (XLPE) compositions for medium and high voltage cable insulation suffer from peroxide migration issues due to solubility limitations and antagonistic interactions among additives, leading to scorch-cure performance variations and increased scrap generation during cable production.
Innovation Solution
Incorporating a dielectric fluid into the crosslinkable ethylene-based polymer composition with a peroxide initiator and a coagent, such as alpha-methyl styrene dimer, to solubilize the peroxide, thereby reducing migration and maintaining scorch-cure performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peroxide is added to crosslinkable polyethylene composition, then crosslinking performance is improved, but peroxide migration to pellet surface occurs
Solution Approach 1:
The patent introduces a peroxide carrier or encapsulation system as an intermediary between the peroxide and the polyethylene matrix. This intermediary prevents direct contact and migration of peroxide to the pellet surface while still enabling crosslinking when activated. The carrier acts as a mediating structure that holds the peroxide in place until the crosslinking process is initiated.
Solution Approach 2:
The patent modifies the physical or chemical parameters of the peroxide or its delivery system to reduce migration. This could involve changing the peroxide from a free state to an encapsulated or bound state, altering its solubility characteristics, or modifying the pellet structure to prevent peroxide migration while maintaining crosslinking capability.
2Stability of the object's composition
If peroxide migration is reduced by lowering peroxide content, then composition stability is improved, but crosslinking performance deteriorates
Solution Approach 1:
The patent divides the peroxide into multiple smaller units or compartments distributed throughout the polyethylene matrix. Instead of using a single high concentration of peroxide that would migrate, the system uses many small peroxide units that are individually contained or distributed in a segmented manner, preventing migration while maintaining sufficient total peroxide content for crosslinking.
Solution Approach 2:
The patent incorporates the peroxide into the polyethylene matrix in advance during compounding, but in a form or location that prevents migration until crosslinking is needed. The peroxide is pre-positioned within the matrix structure or bound to matrix components, ensuring uniform distribution and preventing migration before the crosslinking process is initiated.
3Ease of operation
If multiple additives are added to improve scorch-cure balance, then processing performance is improved, but additive interactions cause formulation instability
Solution Approach 1:
The patent assigns different functional additives to specific locations or phases within the composition. Instead of having all additives uniformly distributed where they can interact antagonistically, the system creates local zones or phases where specific additives are concentrated, allowing each additive to perform its function without interfering with others. This spatial separation maintains formulation stability while preserving scorch-cure balance.
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 addition of a dielectric fluid significantly reduces peroxide migration while maintaining excellent scorch and cure performance, ensuring consistent cable production and improved electrical insulation properties.
Implementation Method 1
the maximum solubility of DCP in LDPE is estimated at around 1 wt % at room temperature
Implementation Method 2
dicumyl peroxide (DCP) as a basis for the formulation
Data Source
AI summary
A composition comprising:A. 91.5 to 97.9% of a crosslinkable ethylene-based polymer, e.g., LDPE;B. 1 to 3% of an organic peroxide, e.g., dicumyl peroxide;C. 1 to 5% of a dielectric fluid, e.g., an alkylated naphthalene; andD. 0.1 to 0.5% of a coagent such as AMSD.The compositions exhibit high cure rates without any significant reduction in scorch resistance, heat ageing and electrical performance, and are particularly useful as insulation sheaths for medium and high voltage power cables.