Multilayer Copolyamide Barrier Pipe for High Temperature Fluid Transport
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Solution Overview
Problem
Current multilayer structures used in the transport and storage of fluids in vehicles face challenges with high temperature resistance, mechanical flexibility, chemical resistance, and barrier properties, particularly as the melting temperature of external polyamide layers is exceeded, leading to degradation and loss of fluid integrity.
Innovation Solution
A multilayer structure comprising an external layer of semi-crystalline copolyamides with a melting temperature of at least 220°C, composed of specific semi-aromatic and aliphatic units, and an internal barrier layer of functionalized tetrafluoroethylene copolymers, ensuring durability and low permeability to fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If highly carbonaceous aliphatic polyamides (PA12, PA11, PA10.10) are used as external layers, then mechanical flexibility, chemical resistance, and low water absorption are improved, but melting temperature remains below 200°C which is insufficient for high temperature applications
Solution Approach 1:
The patent employs composite materials by combining semi-aromatic polyamide (providing high temperature resistance with Tm ≥ 220°C) and aliphatic polyamide (providing mechanical flexibility and chemical resistance) in a multilayer structure. This composite approach allows the external layer to simultaneously achieve both high melting temperature and mechanical flexibility that neither material could provide alone.
2Temperature
If low carbon aliphatic polyamides (PA6, PA6.6, PA4.6) are used to increase melting temperature above 220°C, then temperature resistance is improved, but chemical resistance especially to zinc chloride and water absorption properties deteriorate
Solution Approach 1:
The patent uses composite materials where the external layer combines semi-aromatic polyamide (providing high melting temperature ≥ 220°C) with aliphatic polyamide (providing chemical resistance to zinc chloride and low water absorption). This composite structure resolves the contradiction by allowing both high temperature resistance and chemical resistance to coexist.
3Temperature
If semi-aromatic polyamides (PA6.T/6.I, PA6.T/6.I/6.6) are used to increase melting temperature above 240°C, then temperature resistance is improved, but mechanical flexibility and elongation at break deteriorate due to increased rigidity
Solution Approach 1:
The patent employs composite materials by formulating the external layer with semi-aromatic polyamide (providing high melting temperature ≥ 240°C) combined with aliphatic polyamide (providing mechanical flexibility and elongation at break). This composite approach allows the material to simultaneously achieve high temperature resistance and mechanical flexibility.
4Reliability
If multilayer structures with barrier layers are used to improve fluid barrier properties, then permeability resistance is improved, but the external polyamide layer degrades when exposed to temperatures exceeding its melting point
Solution Approach 1:
The patent applies segmentation by dividing the pipe structure into distinct functional layers: an external layer made of heat-resistant semi-aromatic polyamide (providing thermal stability at temperatures ≥ 220°C) and an internal barrier layer (providing fluid barrier properties). This segmentation allows each layer to perform its specific function without degradation from temperature exposure.
Data Source
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AI summary
The invention relates to a multilayer structure including: a so-called outer layer (L1) consisting of a composition that primarily includes one or more semicrystalline copolyamides (H), the melting point of which is at least 220ºC and which contains at least 80 mol % of the following two units (s) and (a), wherein the (s) unit denotes one or more semiaromatic (s) units consisting of one of more sub-units from aromatic diacid (sr) and one or more sub-units from aliphatic diamine (sa) having 9 to 13 carbon atoms, and the (a) unit denotes one or more aliphatic units having 8 to 13 carbon atoms per nitrogen atom, the molar ratio (s)/(a) being 1 to 3; and a layer (L2) consisting of a composition primarily containing one or more tetrafluoroethylene (TFE) copolymers, said TFE copolymer being necessarily functionalized when layer (L2) is in contact with layer (L1) or with an intermediate layer that primarily includes one or more polyamides. The invention also relates to the uses of said multilayer structure for transporting fluids in the automotive field.