BACT/XT Copolyamide Barrier Structure for Fluid Storage
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Solution Overview
Problem
Current polyphthalamides used in automotive and fluid storage applications lack improved barrier properties, particularly against aggressive bio-fuels, and require enhanced mechanical characteristics like burst strength, flexibility, and low permeability to hydrocarbons and their additives.
Innovation Solution
A barrier structure comprising a high Tg BACT/XT copolyamide layer devoid of strengthening fibers, with specific molar content ranges for BAC and XT units, and optional replacement by other diacids and diamines, providing improved crystallinity and processability for use in multilayer structures for fluid transport and storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyphthalamides are used for fluid storage and transport, then mechanical strength and processability are achieved, but barrier properties against aggressive bio-fuels and hydrocarbons are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the polyamide by incorporating specific cyclic aliphatic diamine units (BAC) with controlled molar content (5-50%) and adjusting the ratio of amine chain ends to acid chain ends to greater than 5. These parameter changes modify the polymer structure to achieve superior barrier properties against bio-fuels while maintaining processability through controlled crystallinity and melting temperature (260-300°C).
2Strength
If strengthening fibers are added to polyamide composites to improve mechanical strength, then burst strength and shock resistance are enhanced, but barrier properties and fuel resistance are compromised
Solution Approach 1:
The patent extracts and eliminates strengthening fibers from the polyamide composition entirely. Instead of using fiber-reinforced composites, the invention achieves the required mechanical strength through the optimized polyamide matrix itself, with specific molecular structure (high Tg, controlled crystallinity) and composition (BAC units with 5-50% molar content) that provides both mechanical integrity and superior fuel resistance without fiber additives.
3Temperature
If the glass transition temperature Tg is increased to improve temperature stability, then high-temperature mechanical properties are enhanced, but crystallization kinetics and processability deteriorate
Solution Approach 1:
The patent optimizes the ratio of amine chain ends to acid chain ends to greater than 5, which creates a molecular structure that achieves high glass transition temperature (improving temperature stability) while simultaneously maintaining favorable crystallization kinetics. This specific compositional parameter allows the polymer to crystallize efficiently during processing despite the high Tg, resolving the contradiction between temperature stability and processability.
Data Source
AI summary
The invention relates to a structure comprising at least one layer (1) comprising a BACT/XT copolyamide in which: —BACT is a unit with an amide moiety having a molar ratio of between 20 and 70%, preferably between 25 and 60%, and more preferably between 35 and 55%, where BAC is chosen from 1,3-bis (aminomethyl) cyclohexyl (1,3 BAC), 1,4-bis (aminomethyl) cyclohexyl (1,4 BAC) and a mixture of same, and T is terephthalic acid, —XT is a unit with an amide moiety having a molar ratio of between 30 and 80%, preferably between 40 and 75%, and more preferably between 45 and 65%, where X is a C9 to C18, preferably C9, C10, C11 and C12, linear aliphatic diamine, and where T is terephthalic acid, preferably a C10, C11 and C12 terephthalic acid.