Epoxy Resin Composition for Short Cure at Low Temperature
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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 not suitable for large-volume resin curing due to increased reactivity and exothermic reactions, limiting their application in composite materials.
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 generates exothermic energy from a low-temperature cure reaction to initiate a high-temperature cure reaction, allowing for rapid curing at temperatures below 120°C and achieving greater than 90% degree of cure in less than 10 minutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature cure reaction is used to achieve high-performance characteristics, then the degree of cure and resin performance are improved, but the cure time increases and exothermic reactions become problematic for large-volume curing
Solution Approach 1:
The curing process is segmented into two distinct reactions: a low-temperature cure reaction that occurs first and generates exothermic energy, followed by a high-temperature cure reaction that is activated by this generated heat. This segmentation allows each reaction to operate in its optimal temperature range, achieving high degree of cure without requiring prolonged high-temperature exposure throughout the entire curing process.
Solution Approach 2:
The exothermic energy, which was previously considered a harmful factor causing uncontrolled temperature rise and degradation, is converted into a beneficial heat source that activates the high-temperature cure reaction. The low-temperature cure reaction's exothermic output serves as the energy input for the high-temperature cure reaction, eliminating the need for external high-temperature heating and significantly reducing cure time.
2Object-affected harmful factors
If low-temperature cure reaction is used to reduce exothermic effects, then curing safety is improved, but the degree of cure and resin performance deteriorate
Solution Approach 1:
The curing system is divided into two sequential reactions with distinct temperature profiles. The first reaction operates at low temperature to minimize exothermic effects and ensure curing safety, while the second reaction operates at high temperature to achieve the required degree of cure and resin performance. This segmentation allows the system to benefit from both low-temperature safety and high-temperature effectiveness.
Solution Approach 2:
The low-temperature cure reaction, while limited in its own degree of cure, generates exothermic energy that is converted into the activation energy needed for the high-temperature cure reaction. This transforms the limitation of low-temperature curing into the advantage of providing controlled heat for the subsequent high-temperature reaction, ultimately achieving both safety and performance.
3Reliability
If high-temperature cure is applied to large-volume resin, then complete curing is achieved, but thermal degradation and exothermic runaways occur
Solution Approach 1:
The curing process is divided into two stages: an initial low-temperature stage that proceeds slowly with minimal exothermic effect, and a subsequent high-temperature stage that is activated by the heat generated in the first stage. This segmentation allows large-volume resin to cure completely without subjecting it to prolonged high-temperature exposure that would cause thermal degradation.
Solution Approach 2:
The low-temperature cure reaction serves the dual purpose of initiating the curing process and generating the heat required for the high-temperature cure reaction. The system is self-heating, eliminating the need for external high-temperature energy input and avoiding the thermal runaway that would occur with conventional high-temperature curing of large-volume resin.
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 properties influenced by high-temperature cure systems, achieved through a short cure time and low cure temperature, resulting in a chemically homogeneous network phase with a glass transition temperature of 110°C-150°C, suitable for advanced composite materials.
Implementation Method 1
the exothermic energy (i.e. heat) generated by a low temperature cure reaction to activate a high-temperature cure reaction
Data Source
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.