Non-halogenated Two-Component Epoxy Adhesive with Flame Retardancy
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Solution Overview
Problem
Current structural adhesives face challenges in achieving rapid curing at room temperature while maintaining high mechanical and adhesive strength, especially at elevated temperatures, and require additional properties like flame retardancy and low smoke/toxic fumes emission, which existing technologies do not adequately address.
Innovation Solution
A curable adhesive precursor comprising a first part with a polyether amine epoxy curing agent, a secondary curative, and a metal salt catalyst, combined with a second part containing distinct epoxy resins, phosphorous-based flame retardants, and a core-shell polymer toughening agent, which are mixed to form a curable adhesive composition that cures quickly and exhibits excellent mechanical and flame retardant properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast curing agents are used to achieve rapid curing at room temperature, then curing speed is improved, but mechanical strength and adhesive strength at elevated temperatures deteriorate
Solution Approach 1:
The curing agent is divided into two distinct components: a primary curing agent that enables fast curing at room temperature, and a secondary curing agent that provides enhanced high-temperature strength. This segmentation allows each component to perform its specific function optimally without compromising the other.
Solution Approach 2:
The patent uses a composite curing system combining multiple curing agents with different functional properties. The primary curing agent (e.g., polyfunctional amine) provides rapid initial cure, while the secondary curing agent (e.g., latent curing agent activated at elevated temperatures) contributes to high-temperature mechanical strength, creating a synergistic effect.
2Object-affected harmful factors
If flame retardant compounds are added to achieve flame retardant properties, then flame retardancy is improved, but the weight of the adhesive increases
Solution Approach 1:
The patent optimizes the concentration and type of flame retardant compounds to achieve the minimum effective amount for flame retardancy. By carefully controlling the parameters of flame retardant addition (type, amount, distribution), the adhesive achieves required flame resistance while minimizing weight increase.
Solution Approach 2:
The patent uses halogen-free flame retardant systems that replicate the flame retardant function of traditional halogenated compounds but with lower molecular weight and better compatibility, avoiding the weight penalty associated with conventional flame retardants while maintaining safety performance.
3Ease of operation
If reactive curing agents are used to enable low temperature curing, then ease of operation is improved, but shelf life deteriorates due to premature cross-linking
Solution Approach 1:
The adhesive system is segmented into two separate components: the epoxy resin base and the curing agent. This segmentation prevents premature reaction during storage while enabling low-temperature curing when mixed. The separate storage of components eliminates the shelf-life problem associated with reactive single-component systems.
Solution Approach 2:
The patent prepares the adhesive components in advance in separate, stable forms that can be stored independently. The reactive curing agent is pre-formulated in a stable state that prevents premature cross-linking, but upon mixing with the epoxy resin, immediately initiates the desired low-temperature curing reaction.
4Object-affected harmful factors
If large amounts of flame retardant compounds are used to achieve strict flame retardant requirements, then flame retardancy is improved, but handling properties and work life deteriorate
Solution Approach 1:
The patent carefully adjusts the concentration, type, and distribution parameters of flame retardant compounds to achieve the threshold for flame retardant compliance while maintaining optimal handling properties. By optimizing these parameters, the adhesive retains good work life and applicability despite the presence of flame retardants.
Solution Approach 2:
The patent uses flame retardant compounds that are compatible with the adhesive matrix and do not significantly interfere with the working life. The formulation allows for the inclusion of sufficient flame retardant to meet safety standards while the overall system maintains adequate open time and handling characteristics for practical application.
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 solution enables fast curing with high mechanical strength, favorable smoke and non-toxic properties, and effective flame retardancy, even at elevated temperatures, making it suitable for industrial applications in aerospace and automotive manufacturing.
Implementation Method 1
a metal salt catalyst
Implementation Method 2
at least one phosphorous-based first flame retardant
Data Source
AI summary
In one aspect of the present disclosure, there is provided an adhesive precursor, comprising a first part (A) comprising: a first epoxy curing agent comprising at least one polyether amine and having an amine equivalent weight of at least 55 grams per mole of amine equivalents; a second epoxy curing agent distinct from the first epoxy curing agent or a secondary curative; a metal salt catalyst; and optionally, a toughening agent; a second part (B) comprising: a first epoxy resin; a second epoxy-based resin distinct from the first epoxy resin; at least one phosphorous-based first flame retardant; a core-shell polymer toughening agent; optionally an epoxy-based reactive diluent; and optionally, a filler material; wherein the total amount of the flame retardant system is lower than 25 wt.-% of the total curable adhesive precursor.