Low-Permeation Flexible Fuel Hose With EVOH Barrier
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Solution Overview
Problem
Conventional flexible fuel hoses fail to meet low permeation standards for alcohol-containing fuels, particularly due to flexibility issues and high permeability rates when using ethylene-vinyl alcohol copolymer (EVOH) with ethylene content above 30 mole %, and require additional fluorinated or thermoplastic layers for adequate impermeability.
Innovation Solution
A flexible fuel hose design featuring a non-fluorinated rubber inner and outer layer with an intermediate EVOH barrier layer having less than 30 mole % ethylene content, optionally reinforced with nylon textile, eliminating the need for additional thermoplastic or fluorinated-polymer layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If EVOH with ethylene content above 30 mole % is used in the barrier layer, then flexibility is improved, but permeability to alcohol-containing fuels increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ethylene content of EVOH to be 30 mole % or less, transforming the material properties to achieve both low permeability and adequate flexibility. This parameter optimization resolves the contradiction by finding the critical threshold value that balances the two opposing requirements.
Solution Approach 2:
The patent uses composite materials by combining EVOH barrier layer with specific rubber materials (NBR, ECO, CSM, or HNBR) having particular properties. The composite structure leverages the permeation resistance of EVOH while the rubber matrix provides flexibility, resolving the contradiction through material composition rather than relying on EVOH flexibility alone.
2Reliability
If fluorinated polymer layers are added to achieve low permeability, then impermeability to alcohol-containing fuels is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies the extraction principle by removing fluorinated polymer layers from the hose construction while maintaining low permeability performance. The simplified structure uses only EVOH (30 mole % or less ethylene) as the barrier layer, eliminating unnecessary complex layers and reducing manufacturing complexity while achieving the same impermeability goal.
Solution Approach 2:
The patent changes the material parameter by using EVOH with ethylene content of 30 mole % or less, which provides sufficient permeation resistance without requiring additional fluorinated layers. This parameter change enables a simpler single-barrier-layer construction that meets performance requirements without increased complexity.
3Reliability
If EVOH layer thickness is increased to reduce permeability, then impermeability is improved, but flexibility and burst strength may be compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the ethylene content of EVOH to 30 mole % or less, which dramatically improves permeation resistance per unit thickness. This allows achieving the required impermeability with a thinner barrier layer that maintains flexibility and does not compromise burst strength, resolving the contradiction between thickness requirements and mechanical 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 solution achieves significantly lower permeation rates, enhanced flexibility, and increased burst strength, meeting stringent SAE standards while reducing the need for fluorinated materials and multi-layer constructions.
Implementation Method 1
low-permeation flexible fuel hose... provide a barrier to alcohol and fuel permeation... EVOH is known to provide a barrier to oxygen, hydrogen, helium, and other gases
Data Source
Figure 1~2
AI summary
A flexible hose having a non-fluorinated rubber inner tube, a non-fluorinated rubber outer cover, an intermediate barrier layer consisting essentially of ethylene- vinyl alcohol copolymer (EVOH) having an ethylene content less than 30 mole %, and preferably a textile reinforcement between said barrier layer and said outer cover. A non-fluorinated rubber tie layer may be included between the barrier and the reinforcement. Permeability to ethanol- and methanol-containing fuels is very low.