Epoxy Adhesive Composition with Hydrazide Curative and Urea Accelerator
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Solution Overview
Problem
Epoxy resin-based adhesives used in aerospace industry face challenges such as short out-life, need for accurate measurement and mixing, limited success in reducing curing time, expansion issues, and retention of mechanical properties under humid conditions, which are inefficient for large-volume industrial applications and structural bonding in Fiber Reinforced Metal Laminates (FML).
Innovation Solution
An adhesive composition comprising an epoxy resin system with a hydrazide curing agent and a urone-based accelerator, specifically adipic dihydrazide and 4,4'-methylene bis(phenyl dimethyl) urea (MDI urone), which is curable at 100-150°C within 30-120 minutes, providing excellent self-adhesive properties and mechanical strength, even at elevated temperatures, without the need for additional curing agents or fillers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two-component epoxy resin adhesive systems are used, then bonding strength and versatility are improved, but the need for accurate measurement and mixing increases complexity and reduces efficiency
Solution Approach 1:
The patent combines the epoxy resin and curative into a single pre-mixed adhesive composition, eliminating the need for separate measurement and mixing of multiple components. This single-component system maintains the bonding strength of epoxy systems while removing the complexity of multi-component handling, directly resolving the contradiction between strength and operational complexity.
Solution Approach 2:
The curative and epoxy resin are pre-combined in the correct proportions during manufacturing, so that when the adhesive is applied, the curing reaction is already primed to occur. This preliminary mixing action eliminates the need for on-site measurement and mixing operations, reducing complexity while preserving the strength benefits of epoxy curing.
2Productivity
If the curing reaction time is reduced by selecting appropriate epoxy resin and curative, then productivity is improved, but the mechanical properties of the adhesive are compromised
Solution Approach 1:
The patent modifies the chemical parameters of the curing system by selecting specific epoxy resin types and curative formulations that enable faster curing kinetics without sacrificing the crosslink density and network structure necessary for mechanical strength. This parameter optimization allows the adhesive to cure quickly while maintaining required mechanical properties.
Solution Approach 2:
The adhesive composition uses a composite curing system combining multiple curatives or a specially formulated curative with the epoxy resin, creating a synergistic effect that accelerates curing while preserving mechanical strength. This composite approach to the adhesive formulation resolves the trade-off between curing speed and final material properties.
3Ease of operation
If a one-component adhesive curable at elevated temperature is used, then ease of operation is improved, but expansion occurs which is not desired for structural bonding
Solution Approach 1:
The patent adjusts the curing temperature parameter and curative selection to achieve curing at lower temperatures or with minimal thermal expansion. By changing the chemical composition and curing parameters, the adhesive can be applied simply as a one-component system while minimizing expansion during the curing process, thus maintaining dimensional stability for structural applications.
4Ease of operation
If the adhesive composition is simplified to reduce mixing requirements, then ease of operation is improved, but the ability to control curing reaction is reduced
Solution Approach 1:
The patent incorporates a latent curative or catalyst system that acts as an intermediary, remaining inactive during storage and application but activating under specific conditions (temperature, humidity, or time). This intermediary mechanism allows the one-component adhesive to maintain simplicity of use while ensuring reliable and controlled curing when needed, resolving the contradiction between ease of operation and curing control.
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 adhesive composition exhibits desirable shear and peel properties, tackiness, and retains mechanical properties under humid conditions, suitable for bonding metal substrates in aerospace applications, with improved handling and storage stability, and enhanced bonding strength for FML applications.
Implementation Method 1
An adhesive composition comprising an epoxy resin system with a curative system comprising a hydrazide curing agent and a urone-based accelerator, which is curable at 100-150°C within 30-120 minutes
Data Source
AI summary
An adhesive composition comprising (a) at least one epoxy resin; and (b) a curative system comprising a hydrazide curing agent, and wherein the curative system further comprises a urone based accelerator.