Polyamide Hose Inner Layer for High-Pressure Hydrogen
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Solution Overview
Problem
Conventional resin hoses and tanks for high-pressure hydrogen fuel-cell electric vehicles suffer from deformation and breakage due to hydrogen permeation and absorption, and have insufficient heat cycle resistance, leading to failure points during repeated charging and discharging.
Innovation Solution
A hose with an inner layer composed of a polyamide resin (A) derived from hexamethylenediamine and an aliphatic dicarboxylic acid, combined with an ethylene/α-olefin copolymer modified with an unsaturated carboxylic acid, providing excellent flexibility and heat cycle resistance, and a reinforcement layer for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional resin tanks and hoses are used for high-pressure hydrogen storage, then the structure is simple and easy to manufacture, but the material undergoes deformation or breakage with repeated charging and discharging due to hydrogen permeation and absorption
Solution Approach 1:
The patent applies composite materials by creating a multi-layer hose structure where the inner layer is made of a specific polyamide resin composition (containing polyamide 6, copolyamide, and impact modifier) that provides excellent gas barrier properties and high impact resistance. This composite approach resolves the contradiction by using materials with inherently low hydrogen permeability while maintaining structural integrity under repeated high-pressure cycling.
Solution Approach 2:
The patent applies local quality by providing different material properties at different locations within the hose structure. The inner layer that contacts hydrogen is made of a specialized polyamide composition with high barrier properties, while other layers can have different characteristics. This localized optimization allows the hose to resist hydrogen permeation and absorption at the critical interface without requiring the entire structure to be complex.
2Reliability
If polyamide resin with high crystalline property is used to reduce hydrogen permeation, then the gas barrier property is improved, but the flexibility and heat cycle resistance deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully controlling the crystalline property of the polyamide resin within a specific range (30% to 70%). This parameter optimization resolves the contradiction by finding the sweet spot where the resin has sufficient crystallinity to provide good hydrogen barrier properties (reducing permeation) while maintaining enough flexibility and heat cycle resistance for practical operation. The balanced composition including impact modifiers further fine-tunes these parameters.
3Ease of operation
If the polyamide resin has low crystalline property for flexibility, then the ease of operation is improved, but hydrogen permeation and absorption increase
Solution Approach 1:
The patent uses composite materials by formulating a multi-component polyamide resin system that combines polyamide 6, copolyamide, and impact modifiers in specific proportions. This composite resin composition achieves a balance where the overall structure provides adequate flexibility while the specific composition reduces hydrogen permeation and absorption compared to simple polyamides with low crystallinity.
Solution Approach 2:
The patent applies parameter changes by optimizing the crystalline property to a specific range (30%-70%) rather than using extreme values. This parameter control ensures that the resin maintains sufficient flexibility for operation while preventing excessive hydrogen permeation that would occur with very low crystallinity materials.
4Duration of action of moving object
If the hose is subjected to repeated heat cycles from -40°C to 90°C during charging and discharging, then the operational capability is improved, but cracks occur at the joint between resin and metal portions
Solution Approach 1:
The patent applies parameter changes by optimizing the polyamide resin composition and its crystalline properties to withstand thermal expansion and contraction during heat cycles. The balanced formulation with controlled crystallinity (30%-70%) and specific additive packages enables the resin to maintain dimensional stability and adhesion to metal components through repeated temperature cycling from -40°C to 90°C without developing cracks at joints.
Solution Approach 2:
The patent uses composite materials in the polyamide resin formulation that provide thermal stability and adhesion promotion. The multi-component system including polyamide 6, copolyamide, and impact modifiers creates a material that can accommodate thermal stresses during charging/discharging cycles while maintaining structural integrity at resin-metal interfaces.
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 hose exhibits improved flexibility, heat cycle resistance, and reduced likelihood of failure points, enabling reliable operation under high-pressure hydrogen conditions.
Implementation Method 1
hydrogen, for its small molecular size, readily permeates through the resins
Implementation Method 2
high-pressure hydrogen, as compared to hydrogen at atmospheric pressure, may be accumulated in the resins in larger amounts
Data Source
Figure 1
AI summary
A polyamide resin composition for a molded article exposed to high-pressure hydrogen contains a polyamide resin (A) including a unit derived from hexamethylenediamine and a unit derived from an aliphatic dicarboxylic acid of 8 to 12 carbon atoms and an ethylene/α-olefin copolymer (B) modified with an unsaturated carboxylic acid and/or a derivative thereof. Provided is a polyamide resin composition that can provide a molded article having excellent flexibility and heat cycle resistance and less likely to suffer failure points despite repeated charging and discharging of high-pressure hydrogen.