Vulcanizable Copolymer Shield Composition for Power Cable Conductivity
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Solution Overview
Problem
Conventional semiconductive shield compositions for power cables face issues with ionic contamination, high viscosity leading to equipment wear, and poor electrical performance due to high carbon black loadings, as well as being costly and prone to corrosion, which results in premature cable failure and increased manufacturing costs.
Innovation Solution
A vulcanizable semiconductive shield composition is developed using a linear, single-site catalyzed ethylene polymer combined with low density polyethylene, specific carbon blacks with low ash and sulfur content, an antioxidant, and a cross-linking agent, which improves dispersion, processability, and electrical properties while reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high carbon black loadings are used to achieve adequate conductivity, then electrical conductivity is improved, but viscosity increases leading to equipment wear and poor extrusion surfaces
Solution Approach 1:
The patent changes the particle size parameter of carbon black from conventional larger sizes to specifically 15-22 nm, and selects carbon blacks with specific Iodine numbers (115-200 mg/g) and DBP numbers (90-170 cm³/100g). This parameter optimization allows achieving adequate conductivity with lower loadings, thus reducing viscosity and equipment wear while maintaining electrical performance
Solution Approach 2:
The patent creates a composite material system combining specifically selected carbon black particles (15-22 nm) with linear single-site catalyzed polyethylene and LDPE/LLDPE. This composite approach optimizes the interaction between filler and polymer matrix, achieving good dispersion and conductivity at lower carbon black loadings, thereby reducing viscosity and equipment wear
2Reliability
If furnace-type carbon blacks are used to provide conductivity, then electrical conductivity is achieved, but ionic contamination increases causing stress gradients and water tree formation
Solution Approach 1:
The patent changes the purity parameters of carbon black by selecting materials with specifically low ash content (≤50 ppm) and low sulfur content (≤50 ppm). This parameter control reduces ionic contamination while maintaining electrical conductivity, preventing stress gradients and water tree formation at the shield/dielectric interface
Solution Approach 2:
The patent replaces expensive high-performance carbon blacks with more economical furnace-type carbon blacks that meet specific purity criteria (low ash and sulfur). By setting minimum performance thresholds rather than using premium materials, the patent achieves adequate conductivity with reduced ionic contamination at lower cost
3Reliability
If acetylene carbon black with high loading is used, then conductivity is improved, but acid formation occurs corroding extrusion die tooling
Solution Approach 1:
The patent changes the sulfur content parameter of carbon black to ≤50 ppm, which significantly reduces the formation of sulfuric acid during processing. This parameter control prevents corrosion of extrusion die tooling while maintaining adequate conductivity through optimized particle size and loading
Solution Approach 2:
The patent converts the potentially harmful high reactivity of acetylene carbon black into a benefit by carefully controlling the sulfur content and using it in combination with antioxidant additives. This approach maintains the good dispersion and conductivity benefits while neutralizing the acid formation issue through compositional balance
4Reliability
If conventional carbon blacks with poor dispersion characteristics are used, then conductivity is achieved, but protrusions and contaminants occur at the shield/dielectric interface
Solution Approach 1:
The patent changes the particle size parameter to 15-22 nm, which is small enough to achieve excellent dispersion in the polymer matrix but large enough to maintain conductivity. This size optimization eliminates protrusions and contaminants at the shield/dielectric interface while achieving adequate conductivity through improved uniform distribution
Solution Approach 2:
The patent applies different quality requirements to different aspects of carbon black: small particle size (15-22 nm) for good dispersion at the interface, specific Iodine numbers for conductivity, and low ash/sulfur for purity. This localized optimization of properties ensures smooth interfaces while maintaining electrical performance
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 composition exhibits superior performance in accelerated water tree testing and impulse strength, with reduced water vapor transmission, smooth interfaces, and lower equipment wear, achieving long-term viability and cost-effectiveness in power cables.
Implementation Method 1
carbon black to provide conductivity for the composition
Implementation Method 2
vulcanizable semiconductive shield composition
Data Source
AI summary
Semi-conductive or insulating compositions including an ethylene/octane or butene copolymer and at least one additional polymer, such LDPE, are described. The compositions may also include carbon black and other additives. The composition may be used as a semi-conductive layer in such applications as electrical cables.