Thermoplastic Cable Insulation Viscosity for High-Temperature Stability
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Solution Overview
Problem
Existing medium and high voltage energy cables face mechanical deformation and electrical breakdown issues due to the inappropriate use of low or high density thermoplastic polyethylene insulation at temperatures above 90°C, as no polyolefin type insulation can withstand 90°C while being easy to use and recyclable.
Innovation Solution
A non-crosslinked polymeric layer made from a thermoplastic polymer with specific capillary viscosity characteristics, such as a capillary viscosity of at most 11000 Pa.s at 170°C and at least 5000 Pa.s at 230°C, is used to provide good mechanical properties at high temperatures, allowing the cable to withstand operational temperatures of 90°C or more, and is easily recyclable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low or high density thermoplastic polyethylene insulation is used, then ease of manufacture and recyclability are improved, but mechanical deformation and electrical breakdown occur at temperatures above 90°C
Solution Approach 1:
The patent changes the rheological parameters of the polyethylene by controlling its capillary viscosity at specific temperatures (170°C and 230°C) and shear rates. This parameter optimization allows the material to maintain processability while achieving the necessary mechanical stability at elevated temperatures up to 90°C, resolving the contradiction between ease of manufacture and mechanical integrity.
2Reliability
If crosslinked polyethylene or ethylene and propylene elastomers are used, then mechanical properties at high temperatures are improved, but ease of manufacture and recyclability deteriorate
Solution Approach 1:
The patent identifies specific capillary viscosity ranges at 170°C and 230°C that enable non-crosslinked polyethylene to achieve mechanical properties comparable to crosslinked materials while maintaining ease of manufacture and recyclability. This parameter optimization allows the material to resist mechanical deformation at 90°C without requiring crosslinking processes.
3Ease of repair
If non-crosslinked thermoplastic polyethylene is used, then recyclability is improved, but the material cannot withstand 90°C operational temperatures
Solution Approach 1:
The patent specifies precise capillary viscosity parameters at 170°C and 230°C that enable non-crosslinked thermoplastic polyethylene to maintain structural stability at operational temperatures of 90°C and above. These rheological parameters ensure the material remains resistant to mechanical deformation while preserving its thermoplastic nature and recyclability.
Data Source
Figure 1
AI summary
The present invention relates to a cable (1) comprising an elongated conductive element (2) surrounded by at least one polymeric layer (3, 4, 5), characterized in that said polymeric layer (3, 4, 5) is a non-crosslinked layer obtained from a composition comprising at least one thermoplastic polymer of the polyolefin type having a capillary viscosity (η) of at most 11000 Pa.s at 170°C, and of at least 5000 Pa.s at 230°C, with a shear of 0.1 s-1.