Crosslinked Cable Insulation via Shear Thinning
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Solution Overview
Problem
The high melt viscosity and filler content in ethylene/propylene (EP) and ethylene/propylene/diene monomer (EPDM) polymers used for crosslinked cable insulation lead to reduced extrusion speed and increased manufacturing costs, along with higher cable density.
Innovation Solution
A crosslinkable polymeric composition comprising an ethylene-based interpolymer with specific properties, such as low density, high-shear viscosity, and shear thinning ratio, and minimal filler content, which is not prepared in a high-pressure reactor, to enhance extrusion efficiency and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fillers such as calcined clay are incorporated to assure adequate pellet stability and melt strength, then sag resistance during extrusion is improved, but extrusion speed is reduced and cable density increases
Solution Approach 1:
The patent changes the rheological parameters of the polymer by controlling the molecular weight distribution (polydispersity index of 3.0 or greater) and using specific ethylene/propylene/diene interpolymer compositions. This allows the material to achieve adequate sag resistance through intrinsic polymer properties rather than filler addition, thereby maintaining higher extrusion speeds and lower cable density.
Solution Approach 2:
The invention extracts the filler component (calcined clay) from the traditional cable insulation formulation. By removing the filler and relying instead on optimized polymer composition with appropriate molecular weight distribution, the patent achieves the desired sag resistance without the negative effects of filler incorporation on extrusion speed and cable density.
2Reliability
If fillers such as calcined clay are incorporated to assure adequate pellet stability and melt strength, then sag resistance during extrusion is improved, but manufacturing cost increases
Solution Approach 1:
The invention removes the filler component (calcined clay) from the formulation, thereby eliminating the additional material cost associated with fillers. The sag resistance is achieved through optimized polymer composition and molecular weight distribution, which reduces overall manufacturing costs while maintaining cable quality.
3Reliability
If high melt viscosity polymers are used to ensure adequate sag resistance, then extrusion speed is reduced, but melt strength is improved
Solution Approach 1:
The patent optimizes the molecular weight distribution parameters, specifically using interpolymers with a polydispersity index of 3.0 or greater. This parameter change allows the material to exhibit appropriate melt strength during extrusion while maintaining lower viscosity that enables higher extrusion speeds, resolving the contradiction between these two properties.
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 results in improved extrusion speed, reduced cable density, and lower manufacturing costs while maintaining adequate sag resistance and crosslinking properties.
Implementation Method 1
an ethylene-based interpolymer having the following properties: (i) a density of 0.91 g/cm³ or less, (ii) a high-shear viscosity (V100) at 100 s⁻¹ of 600 Pa·s or less, and (iii) a shear thinning ratio (V0.1/V100) at 190 °C and 10% strain of at least 8
Data Source
AI summary
Crosslinkable polymeric compositions comprising (a) 10 to 99 weight percent of an ethylene-based interpolymer having the following properties: (i) a density of 0.93 g/cm3 or less, (ii) a high-shear viscosity (V100) at 190 °C and 10 % strain of 1,200 Pa-s or less, and (iii) a shear thinning ratio (V0.1/V100) at 190 °C and 10 % strain of at least 8; and (b) 0 to less than 10 weight percent of a filler, where the ethylene-based interpolymer is not prepared in a high-pressure reactor. Such crosslinkable polymeric compositions may be employed as insulation layers in flexible power cables.