Silane Crosslinkable Polyethylene Blend for Power Cable Semiconducting Layers
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Solution Overview
Problem
Existing silane-crosslinkable polymer compositions for semiconducting layers in power cables face challenges with processability and flexibility due to high viscosity and premature crosslinking, limiting their application in wire and cable production.
Innovation Solution
A polymer composition is developed by blending less than 59 wt% of silane crosslinkable polyethylene with a thermoplastic polyolefin free from silane groups and a filler with a BET Nitrogen Surface Area larger than 3 m2/g, allowing for improved processability and crosslinking properties, including high gel content and good hot set properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of silane groups is increased to improve crosslinking degree, then the gel content increases, but the viscosity increases and processability deteriorates
Solution Approach 1:
The patent changes the chemical parameters of the silane groups by specifying particular types (vinyl silane, allyl silane, γ-methacryloxy propyl silane) with specific functional groups. This parameter change allows for controlled crosslinking reactivity that achieves high gel content (≥40%) while maintaining processability, as these specific silane types provide optimal balance between crosslinking efficiency and viscosity control during processing
Solution Approach 2:
The patent creates a composite polymer system by combining silane-grafted polyethylene with conventional polyethylene or polypropylene in specific ratios (30-70 wt% silane-grafted polymer). This composite approach allows the non-crosslinking polymer matrix to maintain low viscosity and good processability while the silane-grafted portion provides the crosslinking network for high gel content and improved mechanical properties
2Reliability
If free radical generating agents are added to graft silane groups, then silane crosslinking is achieved, but crosslinking side-reactions occur increasing viscosity
Solution Approach 1:
The patent optimizes the concentration parameters of free radical generating agents (0.1-5 wt% relative to total polymer) and silane group content (1-10 wt%) to achieve efficient crosslinking with minimal side-reactions. By carefully controlling these parameters, the patent reduces unnecessary crosslinking that would increase viscosity and energy requirements, while still achieving the target gel content of at least 40%
Solution Approach 2:
The patent uses silane-grafted polyethylene as an intermediary component that mediates between the free radical generating agents and the final crosslinked network. The silane groups act as controlled intermediaries that undergo hydrolysis and condensation reactions to form crosslinks, rather than direct polymer-polymer crosslinking. This intermediary mechanism provides controlled crosslinking efficiency while minimizing energy input and unwanted side-reactions
3Reliability
If filler content is increased to provide conductivity, then the desired electrical properties are achieved, but the viscosity of the polymer material increases
Solution Approach 1:
The patent employs a composite formulation combining silane-grafted polyethylene, conventional polyethylene or polypropylene, and conductive filler (carbon black, graphite, or metal powder) in optimized ratios. The non-crosslinking polymer matrix (conventional PE or PP) acts as a viscosity-reducing component that maintains processability even with 10-50 wt% filler content, while the silane-grafted polymer provides crosslinking for final mechanical strength and the filler provides conductivity
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 solution enables efficient crosslinking with reduced silane content, enhancing the mechanical and thermal properties of the polymer composition, improving production efficiency and maintaining high performance specifications for semiconducting layers in power cables.
Implementation Method 1
by hydrolysing hydrolysable silane groups
Implementation Method 2
subsequently condensing the formed silanol groups
Implementation Method 3
by radical reaction using free radical generating agents
Data Source
AI summary
This invention relates to silane moisture curable polymer composition and more particularly, to such a polymer composition that is highly diluted by a non-silane containing component, while retaining good high temperatures properties. The invention is a polymer composition comprising a base resin comprising less than 59 wt % of a silane crosslinkable polyethylene (A), an thermoplastic polyolefin free from silane groups (B) wherein the polymer composition comprise a filler with a BET Nitrogen Surface Area larger than 3 m2/g (C). The invention also relates to a cable layer of such polymer composition suitably a semiconducting layer of a power cable.