Semiconductive Polymer Composition for Power Cable Insulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductive compositions used in power cables, particularly those with EVA as a polymer component, face issues such as thermal degradation, corrosion, and uneven surface smoothness due to carbon black distribution, leading to potential electrical stress concentrations and reduced service life.
Innovation Solution
A semiconductive polymer composition comprising at least 30 wt% ethylene vinyl acetate copolymer, 25 wt% carbon black, and 2 wt% of an ethylene vinyl acetate copolymer with an MFR2 of at least 100 g/10 min, along with an acid scavenger, compounded at temperatures below 240 °C to enhance smoothness and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EVA copolymer is used in semiconductive composition, then processability and flexibility are improved, but thermal degradation occurs at elevated temperatures leading to acetic acid formation and polymer backbone unsaturations
Solution Approach 1:
A metal deactivator is introduced as an intermediary substance to counteract the harmful effects of metal ions on the EVA copolymer. The metal deactivator binds to metal ions, preventing them from catalyzing the degradation of EVA at elevated temperatures, thus maintaining both processability and thermal stability
Solution Approach 2:
The invention modifies the chemical environment by introducing a metal deactivator that changes the interaction between metal ions and the EVA copolymer. This parameter change prevents the catalytic degradation pathway while preserving the desired processing characteristics of EVA
2Manufacturing precision
If larger carbon black particles are used, then surface smoothness of semiconductive layer is improved, but resistivity of the composition increases
Solution Approach 1:
The invention changes the particle size parameter of carbon black from conventional smaller sizes to larger sizes (5-50 μm). This parameter change improves surface smoothness by reducing the number of particles and minimizing surface irregularities, while the resistivity increase is managed through optimized composition formulation
Solution Approach 2:
The invention applies local quality by using larger carbon black particles that create a smoother local surface topology. The reduced particle count and larger spacing between particles result in a more uniform surface that reduces electrical stress concentration, despite the inherent resistivity trade-off
3Stability of the object's composition
If compounding temperature is elevated to ensure complete mixing, then homogeneity is improved, but thermal degradation of EVA and corrosion of equipment occur
Solution Approach 1:
A metal deactivator serves as an intermediary that allows processing at lower temperatures by preventing metal-catalyzed degradation. This intermediary enables sufficient mixing homogeneity to be achieved at reduced temperatures without the harmful effects of thermal degradation and equipment corrosion
Solution Approach 2:
The invention converts the potential harm of metal ions (which cause degradation at elevated temperatures) into a benefit by using metal deactivators that selectively bind these ions. This transforms the degradation risk into a protective mechanism that enables lower temperature processing while maintaining composition homogeneity
Data Source
AI summary
The invention provides a semiconductive polymer composition comprising a) at least 30 wt% of an ethylene vinyl acetate copolymer; b) at least 25 wt% carbon black; and c) at least 2 wt% of an ethylene vinyl acetate copolymer with an MFR2 of at least 100 g/10 min; with the proviso that components (a) and (c) are different.