High-Vinyl Polyethylene Composition for Cable Extrusion Stability
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Solution Overview
Problem
Existing polyethylene materials used in cable applications face challenges such as premature crosslinking, volatile peroxide decomposition products, and insufficient sagging resistance, leading to issues like scorch, uneven surfaces, and reduced production efficiency in cable manufacturing.
Innovation Solution
A polyethylene with a melt flow rate (MFR 2) between 0.5 and 1.70 g/10 min and a total vinyl group content of 1.10 to 3.0 per 1000 carbon atoms, combined with balanced complex viscosities at 300 rad/sec and 0.05 rad/sec, enabling improved sagging resistance and processability, reducing volatile decomposition products, and maintaining a desirable crosslinking degree.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the extrusion temperature is increased to improve melting and homogenisation, then the polymer composition melts better, but the crosslinking agent decomposes prematurely causing scorch
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating specific comonomers (1,7-octadiene, 1,9-decadiene, or 1,11-dodecadiene) in controlled amounts (0.1-10 wt%). This compositional change modifies the polymer's rheological properties and crosslinking behavior, allowing for lower extrusion temperatures that prevent peroxide decomposition while still achieving proper melting and homogenisation.
Solution Approach 2:
The patent creates a composite polymer system by combining polyethylene with specific diene comonomers and controlled amounts of peroxide crosslinking agents. This composite structure enables the material to achieve both good processability at lower temperatures and effective crosslinking, resolving the contradiction between temperature requirements for melting versus temperature sensitivity of the crosslinking agent.
2Productivity
If the crosslinking agent amount is increased to achieve desired crosslinking degree, then the crosslinking speed increases, but the volatile decomposition products increase causing quality issues
Solution Approach 1:
The patent changes the chemical structure parameters of the polymer by incorporating diene comonomers that provide additional unsaturation. This allows the system to achieve the desired crosslinking degree with lower peroxide concentrations (0.01-5 wt%), thereby reducing volatile decomposition products while maintaining crosslinking speed through the combined effect of peroxide and diene-based crosslinking pathways.
3Strength
If the melt flow rate is decreased to improve sagging resistance, then the sagging resistance improves, but the processability deteriorates
Solution Approach 1:
The patent optimizes the molecular weight distribution and comonomer content parameters to achieve a balanced rheological profile. The specific incorporation of 1,7-octadiene, 1,9-decadiene, or 1,11-dodecadiene (0.1-10 wt%) modifies the polymer chain structure to provide both adequate sagging resistance and improved processability, allowing the material to flow better during extrusion while maintaining structural integrity.
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 polyethylene achieves balanced sagging resistance and processability, minimizing scorch formation and volatile decomposition products, enhancing cable production efficiency and quality, particularly in large cable constructions.
Implementation Method 1
The crosslinking can be performed with crosslinking agents where the crosslinking agents decompose generating free radicals. Such crosslinking agents, e.g. peroxides
Implementation Method 2
crosslinking agents where the crosslinking agents decompose generating free radicals
Implementation Method 3
The elevated temperature will increase the decomposition rate of the crosslinking agents and will thus increase crosslinking speed
Implementation Method 4
The elevated temperature will increase the decomposition rate of the crosslinking agents
Implementation Method 5
the decomposition of the crosslinking agents, e.g. peroxides, during the crosslinking, will further also result in formation of peroxide decomposition products
Implementation Method 6
Some of the peroxide decomposition products are volatile, and their main component is methane
Data Source
AI summary
The invention relates to a polyethylene having a melt flow rate at (2.16) kgloading (MFR 2 ), determined according to method ISO1133-1:2011, which MFR 2 is A g/10 min and A1 ≤ A ≤ A 2; wherein A1 is (0.5) and A 2 is (1.70), and containing a total amount of vinyl groups which is B vinyl groups per (1000) carbon atoms, and B1 ≤ B, wherein B1 is (0.45), determined according to method ASTM D6248-98, a polymer composition, an article being e.g.a cable, e.g. a power cable, and processes for producing a polyethylene,apolymer composition and an article, and an article; useful in different end applications, such as wire and cable (W&C) applications.