Cross-linked Polyethylene Pipe with EVOH Oxygen Barrier
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Solution Overview
Problem
Cross-linked polyethylene pipes used for water systems suffer from oxygen penetration, leading to metal oxidation due to increased oxygen content, which compromises their heat and pressure resistance.
Innovation Solution
A method is introduced to produce a plastic pipe with layers, where a low oxygen penetration polymer like ethyl vinyl alcohol (EVOH) is incorporated between cross-linked polyethylene layers, using organic peroxide additives to cross-link the layers without a separate adhesion polymer, ensuring binding and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cross-linked polyethylene is used for water pipes, then heat and pressure resistance is improved, but oxygen penetration increases causing metal oxidation
Solution Approach 1:
The patent applies composite materials by combining cross-linked polyethylene (for heat and pressure resistance) with ethyl vinyl alcohol (for oxygen barrier properties) in a multi-layer pipe structure. The EVOH layer is positioned between the cross-linked polyethylene layers to create a composite pipe that simultaneously achieves both heat resistance and oxygen barrier functionality.
2Object-affected harmful factors
If ethyl vinyl alcohol layer is added to reduce oxygen penetration, then oxygen barrier performance is improved, but adhesion to polyethylene becomes problematic
Solution Approach 1:
The patent uses an adhesion layer as an intermediary between the ethyl vinyl alcohol layer and the cross-linked polyethylene layers. This adhesion layer has compatibility with both materials, enabling effective bonding between the EVOH barrier layer and the polyethylene structural layers, thus resolving the adhesion problem caused by the poor bonding affinity between EVOH and polyethylene.
3Object-affected harmful factors
If ethyl vinyl alcohol is used as outermost layer for oxygen protection, then oxygen barrier performance is maximized, but water solubility causes durability issues
Solution Approach 1:
The patent applies local quality by positioning the ethyl vinyl alcohol layer in the middle of the pipe wall, surrounded by water-resistant cross-linked polyethylene layers on both the inner and outer surfaces. This arrangement allows the EVOH to provide its oxygen barrier function where needed while the outer polyethylene layer protects it from water exposure and mechanical damage.
4Object-affected harmful factors
If multiple layers with adhesion polymers are used, then oxygen barrier performance is improved, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple layers into a simplified three-layer structure: outer cross-linked polyethylene layer, middle ethyl vinyl alcohol layer, and inner cross-linked polyethylene layer. The adhesion properties are achieved through the chemical structure of EVOH itself and the use of organic peroxide for cross-linking, reducing the need for separate adhesion polymer layers while maintaining effective bonding between layers.
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
This approach reduces oxygen penetration, enhancing the pipe's heat and pressure resistance while maintaining the benefits of cross-linked polyethylene, thus meeting or exceeding performance standards with fewer layers.
Implementation Method 1
using organic peroxide additives to cross-link the layers without a separate adhesion polymer, ensuring binding and protection
Data Source
AI summary
The object of the invention is a method to produce plastic pipe where a pipe of two or more layers is extruded and where at least one layer has additive that by heat treatment releases free radicals. Immediately after the extrusion, the pipe is heat treated by leading it either through a hot salt bath or an infra-red radiation so that the mentioned additive decomposes. Now, the layer(s) having additive get cross-linked and additionally the crosslinked layer(s) fix with chemical bonds to at least one other layer.With this method it is possible to produce a plastic pipe where there is no need to use a separate adhesion plastic layer to fix to each other layers that reject each other.