Thermosetting Epoxy Resin Bonding Dissimilar Substrates
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Solution Overview
Problem
Thermosetting epoxy resin compositions fail to provide adequate mechanical properties and durability when bonding substrates with different coefficients of thermal expansion, leading to adhesive bond failure, deformation, or 'freezing' of tension, making them sensitive to static, dynamic, and shock stresses.
Innovation Solution
A method involving a one-component thermosetting epoxy resin composition with an epoxy resin having multiple epoxy groups, a latent curing agent, and a toughness improver, specifically a terminally blocked polyurethane prepolymer, applied to substrates and heated to 100-220°C, ensuring a maximum linear expansion of ≥1.65 mm during cooling, thereby enhancing the epoxy resin's tolerance to thermal expansion differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermosetting epoxy resin composition is used for bonding substrates with different coefficients of thermal expansion, then structural bonding strength is achieved, but high tension develops during cooling causing adhesive bond failure or deformation
Solution Approach 1:
The patent modifies the chemical composition parameters of the epoxy resin by incorporating specific flexible chain compounds and toughening agents, changing the material's physical properties to accommodate thermal expansion differences while maintaining bond strength
Solution Approach 2:
The invention creates a composite adhesive system combining epoxy resin with flexible chain compounds and toughening agents, leveraging the complementary properties of each component to achieve both strength and thermal expansion tolerance
2Ease of manufacture
If substrates with different coefficients of thermal expansion are bonded together, then structural assembly is achieved, but high tension during cooling leads to deformation of substrates
Solution Approach 1:
The adhesive composition is modified to change its thermal and mechanical parameters, specifically incorporating flexible chain compounds that can accommodate dimensional changes during thermal cycling without transmitting excessive stress to the substrates
3Strength
If conventional epoxy resin is used for structural bonding, then adequate mechanical properties are achieved, but the adhesive bond becomes sensitive to static, dynamic and shock stresses
Solution Approach 1:
The patent develops a composite adhesive material combining epoxy resin with flexible chain compounds and toughening agents, where the flexible chains act as stress absorbers and the toughening agents prevent crack propagation under various stress conditions
Solution Approach 2:
The flexible chain compounds and toughening agents are incorporated into the adhesive formulation in advance to provide cushioning effect against future static, dynamic, and shock stresses that the bonded structure may encounter during its service life
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 method ensures that the bonded substrates withstand high stresses without failure, maintaining mechanical integrity and reducing the risk of adhesive bond weakening due to thermal expansion differences.
Implementation Method 1
If two substrates having different coefficients of linear thermal expansion are bonded to one another by structural bonding, the result of the curing step in the oven at temperatures of 120-220° C. is that the two substrates expand to different lengths.
Data Source
AI summary
A method of bonding substrates having different coefficients of thermal expansion, especially in the shell construction of modes of transport or white goods, using a one-component thermosetting epoxy resin composition containing toughness improvers based on terminally blocked polyurethane prepolymers.