Multilayer Polyamide Tubes for Fuel-Resistant Layer Adhesion
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Solution Overview
Problem
Multilayer tubes with aliphatic and semi-aromatic polyamide layers face challenges in interlayer adhesion durability, particularly when exposed to fuels or heat, and require improvements in chemical resistance and barrier properties.
Innovation Solution
A multilayer tube structure comprising an aliphatic polyamide composition with a specific ratio of methylene groups to amide groups and a semi-aromatic polyamide composition, including elastomer polymers derived from unsaturated compounds, enhances interlayer adhesion and durability while maintaining chemical resistance and low-temperature impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a multilayer tube includes an aliphatic polyamide layer and a semi-aromatic polyamide layer, then chemical resistance and barrier properties are improved, but interlayer adhesion durability deteriorates when exposed to fuel or heat
Solution Approach 1:
The patent introduces a specific aliphatic polyamide composition as an intermediary layer between the semi-aromatic polyamide layer and the fuel/heat environment. This intermediate layer has controlled solubility parameters and molecular structure that enable it to bond effectively with both the semi-aromatic polyamide and resist fuel degradation, thereby maintaining interlayer adhesion durability while preserving chemical resistance.
Solution Approach 2:
The patent modifies the chemical parameters of the aliphatic polyamide composition by controlling the solubility parameter difference between polyamides (1.8-5.5 (MPa)1/2) and adjusting the methylene to amide group ratio (≥8.0). These parameter changes optimize the balance between chemical resistance and interlayer adhesion, preventing the deterioration that normally occurs when exposed to fuel or heat.
2Strength
If conventional monolayer tubes of polyamide resin are used, then strength and flexibility are maintained, but barrier properties to alcohol-containing gasoline are insufficient
Solution Approach 1:
The patent creates a composite multilayer structure combining semi-aromatic polyamide (providing barrier properties) with aliphatic polyamide (providing strength and flexibility). The semi-aromatic polyamide layer, containing specific diamine and dicarboxylic acid units, provides superior barrier properties to alcohol-containing gasoline, while the aliphatic polyamide layer maintains the mechanical strength and flexibility of conventional tubes.
3Strength
If polyamide 11 or polyamide 12 are used as innermost layer, then superior strength and toughness are achieved, but leaching of monomers and oligomers into fuel occurs
Solution Approach 1:
The patent replaces the conventional polyamide 11 or 12 innermost layer with a specifically designed aliphatic polyamide composition that has reduced tendency to leach monomers and oligomers. While this layer may have slightly different mechanical properties, it provides sufficient strength and toughness while eliminating the harmful leaching effect, making it a superior replacement for the conventional material.
Data Source
AI summary
A multilayer tube is provided which includes a layer including a specific aliphatic polyamide composition and a layer including a semi-aromatic polyamide composition including a semi-aromatic polyamide with a specific structure, these layers being adjacent to each other, wherein the aliphatic polyamide composition includes an aliphatic polyamide having a specific ratio of the number of methylene groups to the number of amide groups, a polyamide having a specific difference in absolute value of solubility parameter SP from the aliphatic polyamide, and an elastomer polymer including a structural unit derived from an unsaturated compound having a carboxyl group and/or an acid anhydride group.