Curable epoxy composition and short-cure method
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Solution Overview
Problem
Current epoxy resin systems require high temperatures and long cure times to achieve high-performance characteristics, but these conditions are often impractical for large-scale production, and existing rapid-cure systems result in resins with low glass transition temperatures and propensity for exothermic reactions.
Innovation Solution
A resin composition combining multifunctional epoxy resins with aliphatic or cycloaliphatic amines and aromatic amines, optionally with imidazole as a curing accelerator, which utilizes exothermic energy from a low-temperature cure reaction to initiate a high-temperature cure reaction, allowing for rapid curing at temperatures below 120°C to achieve high glass transition temperatures and greater than 95% degree of cure within minutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature curing is used to achieve high-performance resin properties, then glass transition temperature and mechanical properties are improved, but curing time and energy consumption increase significantly
Solution Approach 1:
The patent changes the chemical parameters of the curing system by combining multiple curing agents with different reactivity profiles (aliphatic amine, aromatic amine, and imidazole) to create a multi-stage curing reaction that maintains high performance while reducing cure time and temperature requirements
Solution Approach 2:
The patent creates a composite curing system using multiple curing agents in specific ratios (aliphatic amine: 30-70 wt%, aromatic amine: 10-50 wt%, imidazole: 1-10 wt%) to achieve synergistic effects that resolve the contradiction between performance and curing efficiency
2Productivity
If rapid-cure systems are used to reduce curing time, then curing speed is improved, but glass transition temperature decreases and exothermic reactions increase
Solution Approach 1:
The patent adjusts the chemical composition parameters by incorporating aromatic amines and imidazoles in controlled amounts to maintain high glass transition temperature (>100°C) while achieving rapid cure rates of less than 10 minutes
Solution Approach 2:
The patent uses imidazole as an intermediary curing accelerator that mediates between the aliphatic and aromatic amine curing agents, enabling rapid initial cure while maintaining final network structure quality and glass transition temperature
3Ease of manufacture
If aliphatic amine curing agents are used to achieve low-temperature curing, then ease of manufacture is improved, but exothermic reactions and resin stability worsen
Solution Approach 1:
The patent modifies the thermal parameters of the curing reaction by combining aliphatic amines with aromatic amines and imidazoles, creating a multi-stage exotherm profile that reduces peak temperature and improves stability while maintaining low-temperature cure capability
Solution Approach 2:
The patent converts the potentially harmful exothermic reaction into a beneficial multi-stage curing process where the exotherm from aliphatic amine reaction provides heat for subsequent aromatic amine reaction, improving overall cure efficiency while controlling peak temperatures
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
This method enables the production of a cured resin matrix with high glass transition temperatures and rapid curing times, achieving comparable mechanical properties to traditional systems in significantly shorter times, while minimizing exothermic energy release and maintaining low cure onset temperatures.
Implementation Method 1
the exothermic energy generated by a curing reaction occurring at low temperature can be used to activate an otherwise energetically inaccessible reaction
Data Source
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AI summary
Disclosed herein is a method for utilizing the exothermic energy generated by a low temperature cure reaction to access a high-temperature cure reaction, which is otherwise energetically inaccessible at a chosen tool temperature, thereby producing a cured resin matrix with properties closely matching to those produced via high-temperature cure reactions but achieved via a short cure time and low cure temperature. Also disclosed is a short-cure resin composition containing: (a) at least one multifunctional epoxy resin having an epoxy functionality of greater than 1; (b) a hardener composition containing (i) at least one aliphatic or cycloaliphatic amine curing agent having one or more amino groups per molecule; (ii) at least one aromatic amine curing agent having one or more amino groups per molecule; and optionally, (iii) an imidazole as curing accelerator. The improved properties of this resin composition include being curable at a temperature of ≤ 120°C for a time period of less than 10 minutes to achieve a degree of cure higher than that derived from the same composition with just (i) aliphatic/cycloaliphatic amine or (ii) aromatic amine in isolation.