Semiconducting Shield Composition for Strippable Cable Insulation
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Solution Overview
Problem
Current cable technologies require high adhesion to remove the second semiconducting shield layer from the insulation layer, making cable installations more difficult.
Innovation Solution
A composition comprising 45-52% ethylene vinyl acetate, 30-45% carbon black, 5-20% acrylonitrile butadiene rubber, 0.2-2% phenolic antioxidant, and 0.5-2% organic peroxide is used to create a second semiconducting shield layer that reduces adhesion, facilitating easier removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional semiconducting shield compositions (EVA with 33% VA, NBR, carbon black, hindered amine antioxidants, and organic peroxide) are used, then the shield layer provides adequate mechanical strength and electrical properties, but the strip force exceeds 15 lb/0.5'' making cable installation difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the EVA copolymer, specifically reducing the vinyl acetate content from the traditional 33% to a range of 28-45%, and optimizes the ratio of polymer components (EVA 45-52%, NBR 5-20%, carbon black 30-45%). These parameter changes result in reduced adhesion to the insulation layer while maintaining adequate mechanical strength and electrical conductivity, achieving a strip force of less than 15 lb/0.5''
Solution Approach 2:
The patent creates a composite material system combining EVA copolymer with NBR and carbon black in specific proportions. This composite formulation synergistically provides the desired properties: EVA provides the base matrix and adhesion control, NBR enhances flexibility and processability, and carbon black provides electrical conductivity and reinforcement. The composite approach allows optimization of multiple properties simultaneously to achieve easy stripability
2Ease of operation
If the adhesion between the second semiconducting shield layer and insulation layer is reduced to improve ease of removal, then cable installation becomes easier, but the mechanical bonding strength may be compromised
Solution Approach 1:
The patent carefully adjusts the chemical composition parameters to achieve differential adhesion properties. By controlling the VA content in EVA (28-45%) and the ratio of polymer components, the formulation achieves reduced adhesion to the insulation layer for easy removal, while maintaining adequate internal bonding strength within the shield layer itself and sufficient electrical conductivity through optimized carbon black content (30-45%)
Data Source
AI summary
A wire or cable comprising an insulation layer and a semiconducting shield layer over and in contact with the insulation layer and strippable from the insulation layer, the second semiconducting shield layer made from the composition comprising: (A) 45-52% ethylene vinyl acetate (EVA) comprising 28-45% units derived from vinyl acetate (VA) based on the weight of the EVA; (B) 30-45% carbon black having (1) 80-1 15 milliliters per 100 grams (ml/100 g) DBP absorption value, (2) 30-60 milligrams per gram (mg/g) iodine absorption (I2NO), and (3) 0.3-0.6 grams/milliliter (g/ml) apparent density; (C) 5-20% acrylonitrile butadiene rubber (NBR) comprising 25-55% units derived from acrylonitrile (AN) based on the weight of the NBR; (D) 0.2-2% phenolic antioxidant; and (E) 0.5-2% organic peroxide.