Polyamide 6 Extrusion Composition for High-Pressure Hydrogen Liners
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Solution Overview
Problem
Conventional resin compositions for hydrogen gas tanks suffer from low melt tension, poor drawdown resistance, and thickness deviations during extrusion-molding, leading to defects when exposed to high-pressure hydrogen gas.
Innovation Solution
A polyamide resin composition comprising 70-99 parts by weight of polyamide 6 resin, 1-30 parts by weight of an ethylene/α-olefin copolymer impact modifier modified with unsaturated carboxylic acid, and 0.005-1 parts by weight of a metal halide, with specific melt tension and take-up speed characteristics to enhance extrusion moldability and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polyamide resin composition is used for extrusion-molding, then the molded article can be produced, but the melt tension is low and drawdown resistance is poor causing thickness deviation
Solution Approach 1:
The invention changes the chemical composition parameters of the resin by introducing a specific metal halide (0.003-1 part by weight) and controlling the ratio of polyamide 6 to copolymerized polyamide (95:5 to 50:50). This parameter optimization increases melt tension from conventional low levels to sufficient levels for extrusion-molding, enabling drawdown resistance and thickness uniformity without compromising the molded article production.
2Reliability
If conventional resin composition is used for hydrogen gas tank, then the tank can be manufactured, but hydrogen gas permeates through the resin causing deformation under high-pressure charging and discharging
Solution Approach 1:
The invention creates a composite resin system combining polyamide 6 with copolymerized polyamide containing aromatic rings in the backbone structure. This composite material structure provides both excellent gas barrier properties to resist hydrogen permeation and sufficient structural strength to maintain integrity under repeated high-pressure charging and discharging cycles.
3Productivity
If extrusion-molding is used for long tank liner, then continuous production is possible, but drawdown occurs during molding making it impossible to provide the molded article
Solution Approach 1:
The invention optimizes the resin composition parameters by incorporating metal halide and controlling the polyamide ratio to achieve sufficient melt tension. This enables the extruded material to maintain its shape and resist drawdown during continuous extrusion-molding of long tank liners, ensuring consistent thickness and dimensional accuracy throughout the production process.
4Strength
If polyamide resin composition with impact modifier is used, then impact resistance is improved, but melt tension decreases and extrusion moldability deteriorates
Solution Approach 1:
The invention carefully controls the type and amount of impact modifier (copolymerized polyamide) at 5-50 parts by weight per 100 parts of polyamide 6, and introduces metal halide to enhance melt tension. This balanced parameter selection maintains impact resistance while preventing excessive melt tension loss, preserving sufficient extrusion moldability for continuous production.
Data Source
AI summary
The purpose of the present invention is to provide a polyamide resin composition which has excellent extrusion moldability and melt stability, can suppress the thickness deviation of a molded article low, and can provide an extrusion-molded article suppressing the occurrence of defects even if charging and discharging of high-pressure hydrogen gas are repeated. Provided is a polyamide resin composition for an extrusion-molded article exposed to high-pressure hydrogen gas. The polyamide resin composition contains: 70 to 99 parts by weight of a polyamide 6 resin (A); 1 to 30 parts by weight of an impact modifier (B); and 0.005 to 1 parts by weight of a metal halide (C) with respect to a total of 100 parts by weight of the polyamide 6 resin (A) and the impact modifier (B). The polyamide resin composition has a melt tension of 20 mN or more when measured at 260°C and a take-up speed at strand broke of 30 m/min or more when measured at 260°C.