Multilayer Polyamide Tube Structure for Fuel Barrier Adhesion
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Solution Overview
Problem
Multilayer tubes face issues with interlayer adhesiveness and durability, particularly when exposed to fuels and heat, and have insufficient barrier properties against ethanol-containing gasoline.
Innovation Solution
A multilayer tube structure comprising an aliphatic polyamide composition with specific melting points and solubility parameters, combined with a semi-aromatic polyamide composition, and an elastomer polymer containing unsaturated compounds, enhances chemical liquid-barrier properties and interlayer adhesiveness while maintaining low temperature impact resistance and elution resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single-layer tube using polyamide 11 or polyamide 12 is used, then strength, toughness, and chemical resistance are improved, but barrier properties against alcohol-containing gasoline are insufficient
Solution Approach 1:
The patent employs a multilayer composite structure combining polyamide 11 or polyamide 12 with EVOH (ethylene/vinyl acetate copolymer saponified product). The polyamide layer provides strength, toughness, and chemical resistance, while the EVOH layer contributes excellent barrier properties against alcohol-containing gasoline and other chemical solutions, achieving synergistic performance that neither material could achieve alone.
2Strength
If polyamide MXD6 is used as an intermediate layer, then low temperature impact resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and eliminates the polyamide MXD6 intermediate layer from the multilayer structure, retaining only the essential polyamide 11 or polyamide 12 layer directly adjacent to EVOH. This simplification removes the need for complex three-layer construction while maintaining the core functionality of interlayer adhesion and barrier properties, thereby reducing manufacturing complexity.
Data Source
AI summary
It is provided a multilayer tube having a layer containing a specific aliphatic polyamide composition and a layer containing a semi-aromatic polyamide composition which contains a semi-aromatic polyamide having a specific structure or a mixture thereof, and the both layers being disposed adjacent to each other, wherein the aliphatic polyamide composition contains an aliphatic polyamide having a melting point of a specific value or less, and a ratio of the number of the methylene groups to the number of the amide groups is a specific value or more, an aliphatic polyamide having an absolute value of a difference in solubility parameter SP values to that of the aliphatic polyamide being a specific range, and an elastomer polymer containing a constitutional unit derived from an unsaturated compound having a carboxyl group and/or an acid anhydride group.