Epoxy Adhesive with Core/Shell Rubber Particles
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Solution Overview
Problem
Epoxy resin adhesives used for bonding different materials like carbon fiber-reinforced composites and metals face challenges with high moduli of elasticity and low glass transition temperatures, leading to stress issues due to thermal expansion coefficient differences, and existing solutions that reduce modulus also lower glass transition temperatures.
Innovation Solution
A cured adhesive composition is formed by reacting an epoxy resin with polyetherdiamine or polyethertriamine, carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN), and rubber particles with a core/shell structure, which results in low moduli of elasticity and high glass transition temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If plasticizers are used to lower the modulus of elasticity of epoxy resin adhesive, then the modulus of elasticity is reduced, but the glass transition temperature is also reduced
Solution Approach 1:
The invention changes the chemical composition parameters of the adhesive system by introducing a specific curing agent (polyfunctional amine) and rubber particles, transforming the adhesive from a plasticizer-based flexibility system to a crosslinked network system with embedded rubber particles that provides flexibility without sacrificing thermal properties
Solution Approach 2:
The invention creates a composite adhesive system combining epoxy resin, polyfunctional amine curing agent, and rubber particles with core/shell structure, where the rubber particles act as flexible domains within the rigid crosslinked network, achieving low modulus while maintaining high glass transition temperature
2Strength
If conventional adhesives are used for bonding different materials with different thermal expansion coefficients, then bonding is achieved, but stresses occur due to high modulus of elasticity
Solution Approach 1:
The invention changes the mechanical properties parameter (modulus of elasticity) of the adhesive to a lower range (100-800 MPa), allowing the adhesive to deform more easily and accommodate thermal expansion differences between bonded substrates, thereby reducing thermal stress while maintaining bonding strength
3Strength
If impact modifiers are added to reduce modulus of elasticity, then flexibility is improved, but glass transition temperature decreases considerably
Solution Approach 1:
The invention uses rubber particles with core/shell structure where the shell provides protective interface and the core provides flexibility, creating a durable flexible phase that does not degrade thermal properties unlike conventional plasticizers and impact modifiers
Solution Approach 2:
The invention employs a composite approach with rubber particles having core/shell structure, where the core provides flexibility and the shell provides interfacial compatibility with the epoxy matrix, achieving flexibility enhancement without the detrimental effect on glass transition temperature seen with conventional impact modifiers
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 achieves a modulus of elasticity of less than 800 MPa and a glass transition temperature above 100°C, effectively bonding materials with different thermal expansion coefficients while maintaining mechanical strength and performance.
Implementation Method 1
an adhesive composition containing a prepolymer which can be obtained by curing a reaction mixture containing: (a) at least one epoxy resin; (b) at least one polyetherdiamine or polyethertriamine
Implementation Method 2
at least one carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN)
Implementation Method 3
rubber particles having a core/shell structure
Data Source
AI summary
The present invention relates to adhesive compositions containing a prepolymer which can be obtained by reacting a reaction mixture containing: at least one epoxy resin; at least one polyetherdiamine or polyethertriamine; at least one carboxyl-terminated butadiene-acrylonitrile copolymer (CTBN); and rubber particles having a core/shell structure. The invention also relates to methods for curing said compositions, to the cured adhesive compositions thus obtained, to the use thereof for bonding components and to the components thus obtained.