Semiconductive Cable Layer Using Homophasic Propylene Copolymer
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Solution Overview
Problem
Existing semiconductive layers in electric cables, particularly those used in medium-voltage and high-voltage applications, suffer from poor surface quality due to inadequate dispersion of conductive particles, leading to protuberances that can cause premature aging and electric breakdown.
Innovation Solution
A semiconductive layer obtained from a polymer composition comprising a homophasic propylene polymer and a homophasic copolymer of C3-C6 olefin and ethylene, combined with a sufficient amount of conductive filler, such as furnace black, to ensure a smooth surface and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black particles are dispersed in an ethylene-based polymer matrix to form a semiconductive layer, then the layer achieves electrical conductivity, but the particles are difficult to disperse uniformly leading to protuberances and poor surface quality
Solution Approach 1:
The patent changes the polymer matrix parameters by using propylene-based polymers instead of ethylene-based polymers, and specifically uses homophasic copolymers with controlled ethylene content (5-20 mol%) to optimize the dispersion parameters of carbon black particles, achieving both good conductivity and smooth surface
Solution Approach 2:
The patent creates a composite material system combining propylene homopolymer, propylene-ethylene copolymer, and carbon black particles. This composite approach allows the polymer blend to work synergistically with the conductive filler to achieve uniform dispersion and smooth surface morphology
2Manufacturing precision
If heterophasic copolymer with high elastomeric phase content is used to improve surface state, then surface smoothness is enhanced, but the mechanical properties and processing stability deteriorate
Solution Approach 1:
The patent applies local quality by using homophasic copolymer with controlled local ethylene content (5-20 mol%) rather than high elastomeric phase content throughout. This localized optimization of composition provides surface smoothness while maintaining the mechanical strength of the propylene matrix
Solution Approach 2:
The patent changes the compositional parameters from heterophasic with high elastomeric content to homophasic with controlled low ethylene content, optimizing both surface quality and mechanical properties simultaneously
3Reliability
If sufficient conductive filler is added to ensure semiconductive properties, then electrical conductivity is improved, but particle dispersion becomes more difficult and protuberances increase
Solution Approach 1:
The patent changes the polymer matrix parameters to propylene-based homophasic copolymer with specific ethylene content, which alters the interaction parameters between polymer and carbon black particles, enabling better dispersion at sufficient filler loadings
Solution Approach 2:
The patent develops a composite formulation where propylene homopolymer, propylene-ethylene copolymer, and carbon black work together synergistically, with the copolymer acting as a dispersant that enables uniform distribution of conductive filler
Data Source
AI summary
The present invention relates to an electric cable comprising at least one semiconductive layer obtained from a polymer composition comprising at least one homophasic propylene polymer and at least one homophasic copolymer of a C3-C6 olefin and ethylene.