Low-Extraction HNBR Hose Layers Bonded Directly to Polyamide
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Solution Overview
Problem
Existing multilayer hose designs require cumbersome and messy adhesive application processes, often using Substances of Very High Concern (SVHC) ingredients like bisphenol A, which pose health hazards and result in inconsistent adhesion and high permeation rates.
Innovation Solution
A hydrogenated nitrile butadiene rubber (HNBR) formulation with a peroxide cure system that forms strong covalent linkages to polyamide thermoplastics, eliminating the need for adhesives and ensuring low permeation and residue extraction, suitable for fluid conveyance hoses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If external epoxy or acrylic glue is applied to adhere layers together, then adhesion between layers is achieved, but the process becomes cumbersome and messy, and SVHC ingredients like bisphenol A are introduced
Solution Approach 1:
The patent removes the external adhesive layer entirely by incorporating adhesion functionality directly into the HNBR rubber formulation. The rubber composition includes specific compounds (carboxylic acid-containing compounds, hydroxyl-containing compounds, isocyanate compounds) that react with polyamide barrier layers to form covalent bonds, eliminating the need for separate glue application processes and removing SVHC ingredients.
Solution Approach 2:
The adhesive function is merged with the rubber material itself. The HNBR rubber composition is formulated to simultaneously provide elastomeric properties and adhesion to polyamide layers through chemical reactions. This combines the bonding function with the structural material, eliminating the need for a separate adhesive layer and simplifying the manufacturing process.
2Strength
If external glue adhesive is used to bond layers, then adhesion is achieved, but adhesion coverage becomes sporadic and inconsistent
Solution Approach 1:
The rubber composition self-bonds to the polyamide barrier layer through chemical reactions between functional groups in the rubber (carboxylic acid, hydroxyl, isocyanate) and the polyamide. This self-adhesion mechanism ensures consistent coverage across the entire bonding surface without relying on external adhesive application, eliminating sporadic coverage issues.
3Ease of operation
If traditional rubber formulations with waxes and plasticizers are used, then processing ease is improved, but extraction of residues occurs that can foul downstream components
Solution Approach 1:
The patent changes the chemical composition parameters of the rubber formulation by selecting specific compounds with appropriate molecular weights and functional groups. The use of high molecular weight plasticizers (>500 g/mol) and controlled amounts of waxes reduces extractability while maintaining processing properties. The functional groups are selected to provide adhesion without excessive extraction.
4Strength
If adhesive layers are used to bond rubber to polyamide, then bonding is achieved, but permeation rates increase due to imperfect adhesion
Solution Approach 1:
The functional groups in the rubber composition (carboxylic acid, hydroxyl, isocyanate) act as chemical intermediaries that form covalent bonds with the polyamide barrier layer. This chemical mediation creates a strong, continuous bond that maintains the integrity of the barrier layer and prevents permeation pathways that would occur with mechanical adhesion alone.
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 HNBR formulation achieves robust adhesion without adhesives, reducing permeation rates and health hazards, while maintaining high thermal stability and fluid compatibility, meeting SAE J1527 and J30R9 specifications.
Implementation Method 1
a specific peroxide cure system that facilitates strong covalent linkages to polyamide thermoplastic without an intervening adhesive layer
Implementation Method 2
Hydrogenated nitrile rubber (HNBR) is a synthetic compound prepared by hydrogenation of nitrile rubber (NBR). The hydrogenation process allows for enhanced thermal stability up to about 150° C.
Implementation Method 3
components comprising maleic anhydride and malemide functionalities to generate robust covalent linkages to the N terminal amine and/or the carbon backbone of a polyamide thermoplastic resin
Data Source
AI summary
Low permeation barrier- and veneer-style multilayer fuel and air conditioning hoses are provided comprising an HNBR rubber layer directly bonded to a polyamide layer. A low extraction, peroxide cured HNBR thermoset rubber formulation is provided that directly bonds to polyamide thermoplastic during the vulcanization step without the need of external glue adhesive application.