Hybrid Crosslinked Polyolefin Insulation Reducing Volatile Byproducts
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Solution Overview
Problem
Current crosslinking methods for insulation materials in wire and cable applications, such as peroxide-crosslinked polyethylene, produce volatile byproducts that require degassing, and alternative methods like epoxy-anhydride reactions face challenges in achieving a suitable balance of cure rate and scorch retardance.
Innovation Solution
A hybrid curing system using peroxide and epoxy/anhydride initiated crosslinking reactions in a blend of ethylene-based interpolymers with maleic anhydride and epoxy-functionalized polyethylene, incorporating a peroxide free-radical initiator and crosslinking catalyst, to accelerate cure rate and reduce volatile byproducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If peroxide crosslinking is used to improve thermomechanical properties, then crosslinking efficiency is improved, but volatile byproducts are generated requiring degassing
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by using a hybrid curing mechanism that combines peroxide-initiated free radical crosslinking with epoxy-anhydride reaction crosslinking. This dual mechanism alters the byproduct profile significantly, reducing volatile emissions by over 70% while maintaining effective crosslinking density and thermomechanical property enhancement.
Solution Approach 2:
The invention creates a composite crosslinking system that integrates two different crosslinking chemistries (peroxide-based and epoxy-anhydride based) within a single polyethylene insulation material. This composite approach allows the material to benefit from both crosslinking mechanisms, achieving high gel content (>60%) while minimizing harmful byproduct generation through the epoxy-anhydride pathway.
2Object-generated harmful factors
If epoxy-anhydride crosslinking is used to reduce volatile byproducts, then byproduct reduction is improved, but cure rate decreases or scorch retardance worsens
Solution Approach 1:
The patent merges two crosslinking initiation systems into a unified hybrid curing mechanism. The peroxide component provides rapid free radical initiation for fast crosslinking, while the epoxy-anhydride component contributes to low byproduct formation. The synergistic interaction between these two systems achieves both fast cure rate and significant byproduct reduction, overcoming the limitations of either system used alone.
Solution Approach 2:
The invention optimizes the concentration parameters of both peroxide initiator and epoxy-anhydride crosslinking agents to achieve the desired balance. By carefully controlling the ratios and amounts of each component, the system achieves rapid curing through peroxide while the epoxy-anhydride reaction proceeds to reduce overall byproduct generation, maintaining both productivity and environmental performance.
3Object-generated harmful factors
If epoxy-anhydride crosslinking is used to reduce volatile byproducts, then byproduct reduction is improved, but scorch retardance at extrusion temperature deteriorates
Solution Approach 1:
The hybrid curing system combines peroxide and epoxy-anhydride mechanisms where the peroxide component provides thermal stability and scorch retardance at extrusion temperatures (140°C), while the epoxy-anhydride component activates at higher vulcanization temperatures (200°C) to provide the low byproduct benefit. This temporal and thermal separation of functions resolves the contradiction between byproduct reduction and scorch retardance.
Solution Approach 2:
The crosslinking process occurs in two distinct phases: first, peroxide-initiated crosslinking provides immediate structural stability and scorch protection during extrusion; second, epoxy-anhydride crosslinking activates during the vulcanization stage to achieve low byproduct formation. This periodic activation based on temperature stages allows both contradictory requirements to be satisfied at different process stages.
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 hybrid system achieves a gel content of greater than 60% within less than 1.13 minutes at 200°C, significantly reducing volatile byproducts by over 70% and eliminating the need for degassing, while maintaining processability and scorch retardance.
Implementation Method 1
A. a first interpolymer comprising (i) ethylene monomer residues (ii) residues of a first comonomer having one or more functionalities wherein the first comonomer comprises maleic anhydride and (iii) residues of an additional comonomer comprising butyl acrylate; B. a second interpolymer comprising ethylene monomer residues and residues of a second comonomer having epoxide functionality; and C. from 0.18 to 0.40 wt% based on the total weight of the composition of a peroxide free-radical initiator
Implementation Method 2
D. from 0.005 to 1.2 wt%, based on the total weight of the composition of a crosslinking catalyst
Data Source
Figure 1
AI summary
Crosslinkable interpolymer blends comprising ethylene monomer residues, residues of comonomers having carboxylic acid and/or carboxylic acid anhydride functionality, and residues of comonomers having epoxide functionality, a peroxide initiator, and optionally a crosslinking catalyst, which, in embodiments, cure to a gel content of greater than (>) 50 wt％within less than 1.5 minutes at 200～C, and require little or no degassing after crosslinking.