Multilayer Thermoplastic Tube Interlayer Adhesion via Semi-Aromatic Polyamide
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Solution Overview
Problem
Existing multilayer tubing for automotive applications faces challenges in achieving a combination of good salt resistance, high burst resistance, and high flexibility while minimizing the use of intermediate adhesion or tie layers, which are economically undesirable and can increase the number of layers in the hose or tubing.
Innovation Solution
A multilayer tube design comprising a first layer with a semi-aromatic polyamide and an aliphatic homopolyamide, in direct contact with a second layer of poly(caprolactam), eliminating the need for intermediate adhesion layers through coextrusion of melt blends, thereby enhancing interlayer adhesion and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If intermediate adhesion layers are used to bond incompatible polyamide layers, then interlayer adhesion is improved, but the total number of layers increases and manufacturing cost increases
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyamide layers by incorporating specific compatibilizers and adhesion promoters directly into the layer formulations. This allows the layers to bond effectively without requiring separate intermediate adhesion layers, thereby maintaining strong interlayer adhesion while reducing the total number of layers in the multilayer construction.
Solution Approach 2:
The patent uses composite material formulations where polyamide layers are combined with compatibilizers and adhesion promoters within the same layer. This creates a functionally integrated structure that achieves both mechanical strength and interlayer bonding without needing separate intermediate layers, thus simplifying the overall layer structure.
2Ease of manufacture
If polyamide 6 and polyamide 66 are used to reduce material cost, then manufacturing cost is reduced, but chemical resistance to salt solutions and flexibility deteriorate
Solution Approach 1:
The patent creates composite material formulations by combining polyamide 6 or polyamide 66 with specific additives including compatibilizers, adhesion promoters, and functional modifiers. These composite formulations maintain the cost advantages of polyamide 6/66 while imparting enhanced chemical resistance to salt solutions and improved flexibility through the synergistic effects of the incorporated components.
Solution Approach 2:
The patent modifies the chemical and physical parameters of polyamide 6/66 by incorporating specific ratios of compatibilizers and functional additives. This changes the material properties to achieve adequate chemical resistance and flexibility while maintaining the cost benefits of using polyamide 6/66 instead of more expensive polyamide 11/12.
3Reliability
If semi-aromatic copolyamides with 15-40 mole percent aromatic repeat units are used, then salt resistance is improved, but material cost increases
Solution Approach 1:
The patent applies the principle of local quality by incorporating aromatic repeat units at specific concentrations (15-40 mole percent) within the copolyamide structure. This localized incorporation of aromatic content provides the necessary salt resistance in critical areas while avoiding the need to use fully aromatic polymers throughout, thereby optimizing the balance between performance and cost.
Solution Approach 2:
The patent optimizes the aromatic content parameter within a specific range (15-40 mole percent) to achieve the desired salt resistance. By controlling this parameter within an optimal window rather than using maximum aromatic content, the patent achieves adequate chemical resistance while minimizing material cost compared to fully aromatic polyamides.
4Reliability
If multilayer construction is used to achieve desired properties, then performance requirements are met, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges multiple functions into fewer layers by incorporating compatibilizers, adhesion promoters, and functional additives directly within the polyamide layer formulations. This consolidation eliminates the need for separate intermediate adhesion layers and specialized functional layers, achieving the desired performance through a simplified multilayer construction with fewer total layers.
Solution Approach 2:
The patent creates universal layer formulations where each polyamide layer performs multiple functions simultaneously: structural support, chemical resistance, flexibility, and interlayer adhesion. By making each layer multi-functional through careful formulation, the patent reduces the need for specialized intermediate layers, thereby simplifying the overall multilayer construction.
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 solution provides improved salt resistance, burst pressure resistance, and flexibility without the use of intermediate adhesion layers, simplifying the coextrusion process and reducing material costs, while maintaining excellent adhesion between layers.
Implementation Method 1
a1) about 25 to 100 weight percent of a semi-aromatic polyamide whose repeat units consist essentially of about 60 to about 85 molar percent of repeat units of the formula —C(O)(CH2)mC(O)NH(CH2)6NH— (I) wherein m is 8 and/or 10, and about 15 to about 40 molar percent of repeat units of the formula
Implementation Method 2
A multilayer tube design comprising a first layer with a semi-aromatic polyamide and an aliphatic homopolyamide, in direct contact with a second layer of poly(caprolactam), eliminating the need for intermediate adhesion layers through coextrusion of melt blends
Implementation Method 3
a2) 0 to 40 (preferably 10 to 30 weight percent and more preferred 10 to 25%) weight percent of polymeric toughener
Implementation Method 4
a3) 0 to 15 (preferred range 6 -12, and 6 to 9 weight percent) weight percent plasticizer
Data Source
AI summary
Disclosed is a multi-layer tube including:A) a first layer including a first layer composition includinga1) about 25 to 100 weight percent of a semi-aromatic polyamide whose repeat units consist essentially of about 60 to about 85 molar percent of repeat units of the formula—C(O)(CH2)mC(O)NH(CH2)6NH— (I)wherein m is 8 and/or 10, and about 15 to about 40 molar percent of repeat units of the formulaB) a second layer including a second layer composition includingb1) 50 to 100 weight percent of poly(caprolactam);with the proviso that the first layer and second layer are in direct contact; and the weight percents are based upon the total weight of the first layer composition and the second layer composition, respectively.