Multilayer Polyamide Tube for Refrigerant Barrier and Burst Resistance
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Solution Overview
Problem
Current tubular structures for transporting refrigerant fluids in automotive air conditioning systems fail to simultaneously meet the requirements of water permeability, hot bursting resistance, chemical resistance, mechanical strength, flexibility, and thermal resistance, while also being impermeable to refrigerant gases and water, due to the antagonistic properties of long-chain and short-chain polyamides.
Innovation Solution
A multilayer tubular structure comprising at least one layer of long-chain polyamide with 10 to 15 carbon atoms and another layer of short-chain polyamide with 4 to 9 carbon atoms, both with a high percentage of aliphatic units, and optionally a third layer of short-chain polyamide or semi-aromatic polyamide, without continuous fibers, to achieve the necessary properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long-chain polyamides are used, then water permeability is improved, but hot bursting resistance deteriorates
Solution Approach 1:
The tubular structure is divided into multiple layers, with the internal layer made of long-chain polyamide for water permeability and the external layer made of short-chain polyamide for hot bursting resistance. This segmentation allows each layer to specialize in one property, resolving the contradiction between water permeability and hot bursting resistance.
Solution Approach 2:
Different layers of the tubular structure have different material properties tailored to their specific functions. The internal layer has high water permeability while the external layer has high hot bursting resistance, creating local quality differentiation that satisfies both requirements simultaneously.
2Strength
If short-chain polyamides are used, then hot bursting resistance is improved, but water permeability deteriorates
Solution Approach 1:
The tubular structure is divided into multiple layers, with the internal layer made of long-chain polyamide for water permeability and the external layer made of short-chain polyamide for hot bursting resistance. This segmentation allows each layer to specialize in one property, resolving the contradiction between water permeability and hot bursting resistance.
3Reliability
If multilayer structure is implemented, then barrier properties are improved, but device complexity increases
Solution Approach 1:
The barrier function is extracted and assigned to a specific layer (the internal layer based on aliphatic polyamide with 10-15 carbon atoms per nitrogen atom), while the external layer handles mechanical strength. This functional extraction simplifies the overall design by clearly defining the role of each layer.
Solution Approach 2:
The invention uses composite material structure combining different polyamide types in layers. The internal layer uses long-chain polyamide for barrier properties while the external layer uses short-chain polyamide for mechanical strength, creating a composite structure that achieves both barrier performance and structural integrity.
Data Source
AI summary
The present invention relates to a multilayer tubular structure (MLT) for transporting a heat transfer fluid, said multilayer tubular structure comprising: • at least one layer (1) comprising a composition (1) predominantly comprising at least one long-chain polyamide having 10 to 15 carbon atoms per nitrogen atom and comprising at least 50% aliphatic motifs relative to the sum of the motifs present in said long-chain polyamide, • at least one layer (2) situated below said layer (1) comprising a composition (2) predominantly comprising at least one polyamide having 4 to 9 carbon atoms per nitrogen atom, said polyamide comprising at least 50% aliphatic motifs relative to the sum of the motifs present in said polyamide, said composition (2) comprising up to 12% polyolefins, in particular up to 6% by weight of polyolefin, relative to the total weight of said composition (2),and up to 2% by weight of at least one plasticizer relative to the total weight of said composition (2), • optionally a layer (3) comprising a composition (3) as defined for composition (1) or comprising a composition (3') predominantly comprising a short-chain polyamide having 4 to 7 carbon atoms per nitrogen atom and at least 20%, preferably at least 25% by weight of at least one polyolefin relative to the total weight of said composition (3'), or a composition (4) comprising a polyamide comprising at least 50% semi-aromatic units, said layer (1) being free of continuous fibers, said layer (2) being in contact with said transported fluid when said layer (3) is not present, and said layer(s) (2) representing at least 50% of the total thickness of the tube.