MXDT/XT Copolyamide Barrier for Fuel Pipes

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Solution Overview

Problem

Current polyamides used in automotive fuel transport pipes lack effective barrier properties against aggressive biofuels and engine lubricating oils, requiring improved crystallinity, temperature resistance, and impact resistance while maintaining low permeability to hydrocarbons and their additives.

Innovation Solution

A barrier structure comprising a high Tg MXDT/XT copolyamide with a molar rate of MXDT ranging from 5 to 45% and XT from 55 to 95%, devoid of reinforcing fibers, which forms a multilayer structure with other polymers like EVOH, PPS, or PPO, enhancing the barrier properties against fuels.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polyamides are used in fuel transport pipes, then processing is easier and cost is lower, but barrier properties against aggressive biofuels and engine lubricating oils are insufficient

Engineering Contradiction:

Improvebarrier propertiesVSAvoidprocessing difficulty

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent employs composite materials by creating a multilayer structure where the MXDT/XT copolyamide barrier layer is combined with other polymer layers. This composite approach achieves superior barrier properties against aggressive biofuels and engine lubricating oils while maintaining processability through the thermoplastic nature of the copolyamide.

Inventive Principle:

Principle #40Composite materials

2Reliability

If polyamides with improved barrier properties are developed, then permeability to hydrocarbons decreases, but crystallinity and temperature resistance require improvement

Engineering Contradiction:

Improvepermeability resistanceVSAvoidcrystallinity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by precisely controlling the molar composition of the copolyamide (MXDT content between 5-45 mol%), the ratio of amine to acid chain ends (≥5), and the molecular weight distribution. These parameter optimizations simultaneously achieve low permeability to hydrocarbons, improved crystallinity, and enhanced temperature resistance up to 125°C.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If polyamides with high crystallinity are used, then temperature resistance improves, but impact resistance at low temperatures deteriorates

Engineering Contradiction:

Improvetemperature resistanceVSAvoidimpact resistance

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent applies local quality by creating a multilayer structure where different layers serve different functions. The MXDT/XT copolyamide barrier layer provides temperature resistance and barrier properties, while other polymer layers in the multilayer structure compensate for impact resistance at low temperatures, allowing each layer to be optimized for its specific function.

Inventive Principle:

Principle #3Local quality

4Strength

If reinforcing fibers are added to polyamide structures, then mechanical strength improves, but barrier properties against fluids deteriorate

Engineering Contradiction:

Improvemechanical strengthVSAvoidbarrier properties

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies segmentation by separating the mechanical reinforcement function from the barrier function. The MXDT/XT copolyamide barrier layer maintains fluid impermeability without reinforcing fibers, while mechanical strength is provided by the multilayer structure and the inherent properties of the copolyamide, avoiding the permeability issues that would arise from adding fibers.

Inventive Principle:

Principle #1Segmentation

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 MXDT/XT copolyamide structure exhibits superior crystal structure and low permeability to fluids, particularly fuels, offering improved mechanical and thermal resistance, and barrier properties, making it suitable for use in fuel transport applications.

Implementation Method 1

said copolyamide having a melting point of 250°C and a glass transition temperature Tg of 125°C or more

Methodology Applied

Scientific EffectCrystallisation: Crystallisation

Data Source

PatentEP3390494B1Barrier structure made from mxdt/xt copolyamide with a high tg

Publication Date: 2022.06.08 ARKEMA FRANCE SA

AI summary

The invention concerns a barrier structure intended for the storage and/or transport of fluids comprising at least one barrier layer (1) comprising an MXDT/XT copolyamide in which: MXDT is an amide unit present in a molar ratio of between 5 and 45%, preferably between 15 and 45%, and more preferably between 20 and 45%, where MXD represents m-xylylenediamine (MXD) and T represents terephthalic acid, XT is a majority amide unit present in a molar ratio of between 55 and 95%, preferably between 55 and 85%, and more preferably between 55 and 80%, where X is a C9 to C18, preferably C9, C10, C11 and C12, linear aliphatic diamine, and where T is terephthalic acid, said copolyamide having a melting point: 250°C < Tf ≤ 300°C as determined according to standard ISO 1 1357-3 (2013).