Epoxy-Cyanate Adhesive with Core-Shell Rubber for Thermal Impact Resistance
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Solution Overview
Problem
Conventional epoxy adhesive compositions exhibit reduced adhesion and impact resistance at elevated temperatures, and existing thermal-resistant epoxy compositions lack high shear adhesive strength and fast curability.
Innovation Solution
A thermal-resistant epoxy structural adhesive composition is developed, incorporating an epoxy-cyanate ester intermediate with core-shell rubber particles, a tetrafunctional epoxy monomer with flame retardant and core-shell rubber, and monomers with vinyl and multifunctional thiol groups to achieve high adhesive strength, fast curability, and impact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional epoxy adhesive composition is used, then high adhesive strength is achieved, but impact resistance is reduced at low and room temperature due to rigidity of epoxy
Solution Approach 1:
The patent uses a composite system combining epoxy resin with polythiol curing agent and rubber particles. The epoxy resin provides adhesive strength while the rubber particles (5-20 parts by weight per 100 parts epoxy resin) absorb impact energy, and the polythiol curing agent creates flexible crosslinked structures. This composite approach resolves the contradiction between rigidity for strength and flexibility for impact resistance.
Solution Approach 2:
The patent modifies the chemical composition parameters by introducing polythiol curing agents with specific molecular weights and structures, and controlling the ratio of rigid to flexible components. By adjusting these parameters, the cured adhesive achieves both high strength and improved impact resistance at room temperature.
2Strength
If conventional epoxy adhesive composition is used, then high adhesive strength is achieved, but adhesion is rapidly reduced at temperature of 120°C or higher
Solution Approach 1:
The patent changes the chemical composition by selecting specific polythiol curing agents with high thermal stability and controlling their ratio to epoxy resin (0.5-2.0 equivalents). This compositional parameter change enables the adhesive to maintain strength at elevated temperatures up to 150°C while retaining room temperature performance.
Solution Approach 2:
The composite system of epoxy resin, polythiol curing agent, and rubber particles creates a network structure that resists thermal degradation. The polythiol-based crosslinked structure provides thermal stability, allowing the adhesive to maintain both strength and flexibility at high temperatures.
3Temperature
If thermal-resistant epoxy composition is used, then thermal resistance is improved, but shear adhesive strength and curability are reduced
Solution Approach 1:
The patent optimizes the molecular weight and structure parameters of the polythiol curing agent to balance reactivity and thermal stability. By controlling these parameters, the adhesive cures rapidly at room temperature or moderate temperatures while achieving high thermal resistance in the cured state.
Solution Approach 2:
The polythiol curing agent acts as an intermediary that enables both fast curability and thermal resistance. Its specific chemical structure allows rapid reaction with epoxy groups while the resulting crosslinked network provides thermal stability, mediating between the requirements of speed and temperature resistance.
4Temperature
If thermal-resistant epoxy composition is used, then thermal resistance is improved, but shear adhesive strength is reduced
Solution Approach 1:
The patent creates a composite adhesive system where epoxy resin provides baseline strength, polythiol curing agent creates flexible crosslinked networks for high shear strength, and rubber particles provide toughness. This composite approach achieves both thermal resistance and high shear adhesive strength (30 MPa or greater at room temperature, 28 MPa or greater at 150°C).
Solution Approach 2:
The patent introduces rubber particles with specific properties (core-shell structure, specific hardness) to local regions within the adhesive matrix. These localized rubber domains provide stress concentration and energy absorption, enhancing shear strength and toughness while the polythiol-crosslinked matrix maintains thermal resistance.
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 composition demonstrates high shear adhesive strength and thermal resistance at both room and elevated temperatures, while maintaining excellent impact resistance and storage properties, effectively addressing the limitations of existing epoxy adhesives.
Implementation Method 1
an epoxy group of the epoxy resin reacts with the curing agent that connects an epoxy resin compound via polyaddition reaction to obtain a cured product
Implementation Method 2
The latent curing accelerator has a function of accelerating the curing reaction to shorten a curing time and lower a curing temperature
Implementation Method 3
incorporating an epoxy-cyanate ester intermediate with core-shell rubber particles
Implementation Method 4
a monomer having a vinyl group at an end thereof and a monomer having a thiol group at an end thereof are simultaneously introduced to realize high adhesive strength and fast curable properties
Implementation Method 5
high shear adhesive strength such as 30 MPa or greater at room temperature or 28 MPa or greater at 150°C to maintain thermal-resistant properties
Data Source
Figure 1~2
AI summary
The present invention relates to an adhesive composition which realizes high adhesive strength and at the same time has properties of impact resistance and heat resistance and, more specifically, to a structural epoxy adhesive composition which exhibits both high adhesive strength and heat resistance due to a heat-resistant epoxy intermediate prepared according to the present invention, exhibits excellent impact resistance due to uniform dispersion of polymer particles in suitable heat-resistant epoxy monomers, and realizes high adhesive strength and fast curability through simultaneous introduction of monomers respectively having a vinyl group and a thiol group at ends thereof. Thus, the adhesive composition is useful for bonding of eco-friendly automobile parts and industrial parts. The structural epoxy adhesive composition having impact resistance according to the present invention comprises: (a) a first component comprising an epoxy-cyanate ester intermediate and core-shell rubber particles; (b) a second component comprising a flame retardant dispersed in a tetrafunctional epoxy monomer, and core-shell rubber particles; and (c) a third component comprising two types of monomers respectively having a vinyl group and a multifunctional thiol group at ends thereof. Also, a method for preparing a heat-resistant structural epoxy adhesive composition having impact resistance according to the present invention comprises: a first step for mixing, with core-shell rubber particles, an epoxy-cyanate ester intermediate prepared by heating liquid epoxy resin and cyanate ester at 80 °C for 30 minutes, followed by stirring at 100 °C for 3 hours and cooling to room temperature, to prepare a first component; a second step for mixing a tetrafunctional epoxy monomer with a flame retardant, stirring the mixture at 80 °C for 30 minutes, and then mixing the stirred mixture with core-shell rubber particles, followed by stirring at 80 °C for 30 minutes and slowly cooling to room temperature, to prepare a second component; a third step for preparing a third component comprising two types of monomers respectively having a vinyl group and a multifunctional thiol group at ends thereof; and a fourth step for mixing the first component and the second component at room temperature for 10 minutes, adding the third component and a curing accelerator thereto, mixing same while stirring for 30 minutes, and then slowly cooling the resultant mixture to room temperature.