Multilayer Polyamide Tube Structure for Stable Barrier Adhesion

The patent applies composite materials by creating a multilayer tube structure where polyamide 11 or polyamide 12 is combined with other resin layers (such as EVOH, PBT, or PEN) to achieve both mechanical strength and barrier properties. The polyamide layer provides strength, toughness, and flexibility, while the adjacent barrier layer provides resistance to alcohol-containing gasoline, resolving the contradiction between mechanical performance and chemical barrier properties.

The patent applies parameter changes by carefully controlling the solubility parameters of the resins used in each layer. By selecting resins with specific solubility parameter ranges (polyamide 11: 22.0-23.0, polyamide 12: 21.5-22.5, EVOH: 23.5-24.5, PBT: 24.0-25.0, PEN: 23.0-24.0), the patent ensures optimal interlayer adhesion while maintaining barrier properties. This parameter control stabilizes interlayer adhesiveness against fluctuations from extrusion conditions and environmental factors.

The patent applies local quality by assigning different functional properties to different layers of the multilayer tube. The polyamide 6T/66 or polyamide 6T/6I/66 layer is positioned to provide heat resistance where needed, while polyamide 11 or polyamide 12 layers are positioned to provide low-temperature impact resistance in other regions. This spatial distribution of properties allows the tube to exhibit both heat resistance and low-temperature toughness simultaneously.

The patent applies the extraction principle by removing the separate adhesive layer from the multilayer structure. Instead of adding an adhesive layer between polyamide 11/12 and barrier resin layers, the patent achieves direct adhesion by carefully selecting resins with compatible solubility parameters. This eliminates the need for separate adhesive layers and simplifies the manufacturing process while maintaining stable interlayer adhesion.