Multilayer Polyamide Tube Liner for Conductivity Without Cracking
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Solution Overview
Problem
Multilayered tubes for transporting liquid chemicals, particularly fuel, require an innermost layer that is excellent in conductivity, liquid chemical barrier properties, impact resistance, and elongation properties, while minimizing the formation of cracks when inserted into other members.
Innovation Solution
A multilayered tube structure with an innermost layer composed of a polyamide resin containing a dicarboxylic acid unit and a diamine unit, combined with a carbon nanotube and an impact modifier, where the surface projections and cross-sectional agglomerates are controlled within specific limits to ensure optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon nanotube is added to polyamide resin to impart conductivity, then electrical conductivity is improved, but the resin composition becomes difficult to mold and process
Solution Approach 1:
A master batch containing carbon nanotubes and polyamide resin is prepared in advance, serving as an intermediary material that pre-distributes the conductive filler uniformly. This master batch is then blended with additional polyamide resin before molding, eliminating direct handling of pure carbon nanotube-polyamide mixtures that cause molding difficulties while maintaining conductivity.
Solution Approach 2:
The resin composition is divided into multiple components: a master batch portion (containing carbon nanotubes and polyamide resin) and a base polyamide resin portion. This segmentation allows the conductive filler to be concentrated in a manageable portion while the bulk material remains easy to process, resolving the contradiction between conductivity and moldability.
2Ease of manufacture
If conventional resin compositions are used for the innermost layer, then manufacturing is simple, but the layer lacks sufficient impact resistance and elongation properties
Solution Approach 1:
The innermost layer uses a composite resin composition combining polyamide resin with carbon nanotubes and a rubber component. The carbon nanotubes provide conductivity and reinforcement, while the rubber component enhances impact resistance and elongation properties, achieving superior mechanical performance without significantly complicating manufacturing.
3Reliability
If the innermost layer has high conductivity and barrier properties, then safety is improved, but the layer becomes more prone to crack formation when inserted into other members
Solution Approach 1:
The composite resin composition includes a rubber component that acts as a crack-arresting phase. When stress concentrates in the rigid polyamide-carbon nanotube matrix, the rubber particles absorb energy and prevent crack propagation, allowing the layer to maintain high conductivity and barrier properties while resisting crack formation during insertion.
Solution Approach 2:
The resin composition parameters are optimized by controlling the content ranges of carbon nanotubes (0.1-10 parts by mass per 100 parts polyamide resin) and rubber component (5-50 parts by mass per 100 parts polyamide resin). This parameter optimization ensures the innermost layer achieves the necessary safety properties while maintaining sufficient flexibility to avoid cracking during assembly.
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 provides a multilayered tube that is superior in conductivity, liquid chemical barrier properties, and impact resistance, with reduced crack formation and enhanced elongation properties, making it suitable for applications like fuel piping in motor vehicles.
Implementation Method 1
carbon nanotube (C)... excellent in conductivity
Implementation Method 2
PTLs 2 to 5 disclose using a carbon nanotube as a conductive filler
Implementation Method 3
impact modifier (B)... excellent in impact resistance
Data Source
AI summary
There is provided a multilayered tube for transporting liquid chemicals containing an outermost layer and an innermost layer, the innermost layer containing a polyamide (A), an impact modifier (B), and a carbon nanotube (C), wherein the number of projections each having a height of 5 μm or more and a longitudinal width of 20 μm or more, which are present on the surface of the innermost layer, is 2 or less per 1 mm2 of surface area; and the number of agglomerates each having a longitudinal width of 5 μm or more, which are present in the cross section of the innermost layer, is 15 or less per 1 mm2 of cross-sectional area. There is also provided a polyamide resin composition constituting the innermost layer of the multilayered tube for transporting liquid chemicals.