Silane Crosslinked Polyolefin Elastomer Cable Insulation
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Solution Overview
Problem
Existing silane moisture-curable polymer resin compositions for low voltage cables become brittle at low temperatures, and existing methods for improving flexibility require specialized equipment and are limited by the use of elastomers that degrade under peroxide or free-radical sources.
Innovation Solution
A composition comprising at least 60 weight percent silane crosslinkable polyolefin polymer resin and up to 40 weight percent polyolefin polymer elastomer resin, prepared using a metallocene catalyst, which is blended and moisture-cured to achieve improved flexibility without the need for radical grafting processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If silane moisture-curable polymer resin compositions are used for low voltage cables, then crosslinking and insulation properties are achieved, but the material becomes brittle at low temperatures
Solution Approach 1:
The patent combines silane crosslinked polyethylene with polyolefin elastomer to create a composite material system. The silane crosslinked polyethylene provides the crosslinked network and insulation properties, while the polyolefin elastomer phase provides flexibility at low temperatures. This composite approach allows both requirements to be satisfied simultaneously by leveraging the complementary properties of each component.
Solution Approach 2:
The patent modifies the chemical structure and composition parameters of the insulation material by incorporating specific ratios of silane crosslinked polyethylene and polyolefin elastomer. By adjusting the composition parameters and crosslinking density, the material achieves optimal balance between crosslinking strength and low-temperature flexibility, transforming the physical and chemical properties to meet both requirements.
2Temperature
If elastomers are blended with polyethylene during reactive extrusion to improve flexibility, then more flexible resin systems are produced, but special extrusion equipment and peroxide-initiated grafting are required
Solution Approach 1:
The patent extracts the peroxide initiation step and replaces it with a simple mechanical blending process. Instead of using complex reactive extrusion equipment with peroxide dosing systems, the invention simply blends pre-silane-crosslinked polyethylene with polyolefin elastomer using standard extrusion equipment, thereby removing the need for specialized equipment while maintaining flexibility improvement.
Solution Approach 2:
Instead of adding elastomer during reactive extrusion with peroxide grafting (conventional approach), the patent inverts the sequence by first preparing silane crosslinked polyethylene separately, then blending it with elastomer in a simple mixing process. This reversal of the process sequence simplifies the equipment requirements while achieving the same flexibility enhancement.
3Temperature
If elastomers are used to improve flexibility, then resin systems become more flexible, but elastomers that degrade in the presence of peroxide or free-radical sources cannot be used
Solution Approach 1:
The patent introduces silane crosslinked polyethylene as an intermediary material that bridges between the crosslinking requirements and elastomer compatibility requirements. This intermediary material provides the crosslinked network structure without requiring peroxide initiation during the blending process, thereby protecting the elastomer from degradation while maintaining both flexibility and structural integrity.
Solution Approach 2:
The patent converts the potential harm of peroxide exposure to elastomers into a benefit by using silane-based crosslinking instead. The silane crosslinking mechanism avoids free-radical generation during blending, thereby protecting elastomers from degradation. The harm of restricted elastomer selection is converted into the benefit of being able to use a broader range of elastomers that would otherwise be incompatible with peroxide systems.
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 a significantly more flexible material with improved tensile and elongation properties, maintaining performance at low temperatures, as demonstrated by reduced flexural modulus and maintained hot set and tensile strength even at 40% elastomer content.
Implementation Method 1
an alkoxy silane attached to the polyethylene chain is hydrolyzed and then cures under the influence of a suitable catalyst
Implementation Method 2
cured or crosslinked by a moisture cure process whereby an alkoxy silane attached to the polyethylene chain is hydrolyzed and then cures
Implementation Method 3
which has been prepared using at least one metallocene catalyst
Data Source
AI summary
Compositions having at least 60 weight percent, based on the total weight of polymers, have at least one silane crosslinkable polyolefin resin and up to about 40 weight percent, based on the total weight of polymers, of at least one polyolefin elastomer resin, wherein the polyolefin polymer elastomer resin has density of less than or equal to about 0.89 g/cm3 and a melt index, I2, of less than about 50 g/10 mm. and which has been prepared using at least one metallocene catalyst provide improved flexibility, especially low temperature flexibility, while maintaining suitable cure performance and strength compared to the silane crosslinkable polymer resin alone. This composition may be used in cables for low temperature service applications.