Multilayer Hydrogen Barrier Structure for Humidity-Stable EVOH Liners
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Solution Overview
Problem
Current composite hydrogen tanks with monolayer liners, such as impact modified polyamide or polyolefin, exhibit insufficient hydrogen gas barrier properties and shock resistance, while multilayer structures with EVOH layers face challenges in maintaining barrier properties at varying humidity levels.
Innovation Solution
A multilayer structure comprising an inner layer of a first polymer, a middle layer of ethylene-vinyl alcohol copolymer (EVOH) with a water content of 1.1-4 mass %, and an outer layer of a second polymer, where the water-vapour transmission rate of the inner layer is lower than that of the outer layer, optimizing hydrogen gas barrier properties by adjusting water-vapour transmission rates and enhancing mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a monolayer liner made from impact modified polyamide or polyolefin is used, then shock resistance is improved, but hydrogen gas barrier properties deteriorate
Solution Approach 1:
The invention uses a multilayer composite structure combining polyolefin (for shock resistance) and EVOH (for hydrogen barrier properties). The inner layer provides impact resistance while the EVOH layer provides the hydrogen gas barrier, resolving the contradiction between mechanical strength and barrier performance.
Solution Approach 2:
The liner is divided into multiple functional layers: an inner layer for shock resistance and an EVOH layer for hydrogen barrier properties. This segmentation allows each layer to perform its specific function optimally without compromising the other.
2Reliability
If an EVOH layer is added to improve hydrogen barrier properties, then hydrogen gas barrier properties are improved, but the structure becomes more sensitive to humidity variations
Solution Approach 1:
The invention optimizes the EVOH layer's water content locally (1.1-4 mass %) to maintain barrier properties. By controlling the water content within this specific range, the EVOH layer achieves optimal hydrogen barrier performance while being less sensitive to external humidity variations.
Solution Approach 2:
The invention changes the water content parameter of the EVOH layer to a specific range (1.1-4 mass %) to optimize barrier properties. This parameter optimization makes the EVOH layer's performance more stable across varying humidity conditions.
3Ease of manufacture
If the EVOH layer is positioned at the center of the multilayer structure, then manufacturing is simplified, but hydrogen barrier properties deteriorate due to moisture exposure
Solution Approach 1:
Instead of placing the EVOH layer at the center (conventional approach), the invention inverts the arrangement by positioning it as the inner layer adjacent to the hydrogen storage space. This inversion protects the EVOH layer from external moisture while maintaining contact with the hydrogen environment, optimizing barrier 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 multilayer structure achieves improved hydrogen gas barrier properties, mechanical strength, and recyclability by positioning the EVOH layer to face higher humidity levels, thereby enhancing the hydrogen storage and transportation capabilities.
Implementation Method 1
a middle layer comprising ethylene-vinyl alcohol copolymer, wherein a water content of the middle layer is 1.1 mass % or more and 4 mass % or less
Implementation Method 2
Ethylene-vinyl alcohol copolymer (EVOH) is known as an excellent barrier material for different gases, including hydrogen gas
Implementation Method 3
the water-vapour transmission rate measured at 38° C. and 90% RH according to ISO15106-2:2003 of the inner layer is lower than the water-vapour transmission rate measured at 38° C. and 90% RH according to ISO15106-2:2003 of the outer layer
Data Source
AI summary
The present invention relates to a multilayer structure for storing or transporting a gas comprising hydrogen, wherein the multilayer structure comprises at least three layers comprising an inner layer comprising at least one first polymer, a middle layer comprising ethylene-vinyl alcohol copolymer, and an outer layer comprising at least one second polymer, and wherein the water-vapour transmission rate of the inner layer is lower than that of the outer layer. The multilayer structure has excellent hydrogen gas barrier properties. Therefore, the multilayer structure is suitable for a hydrogen storage vessel and a hydrogen transportation pipe.