Anhydride Epoxy Curing System with Latent Accelerator
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Solution Overview
Problem
Anhydride-cured epoxy resin systems require high cure temperatures and long processing times, leading to energy inefficiency and poor hot wet properties, limiting their use in applications involving hot and wet environments, and current accelerators are not stable at higher loadings, causing gelation during storage.
Innovation Solution
A new anhydride curing system with a 50:50 weight ratio of anhydride to combined tertiary amine or imidazole and carboxylic acid, using a lower epoxy to anhydride ratio (1:0.4-0.6) and a hindered latent accelerator, allowing full cure in less than 2 hours at 100°C, reducing waste and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional anhydride curing systems are used, then high temperature stability and good radiation stability are achieved, but high cure temperatures and long processing times are required
Solution Approach 1:
The patent changes the chemical parameters of the curing system by introducing a carboxylic acid-modified accelerator, which alters the reaction kinetics to enable curing at lower temperatures (100°C or below) while maintaining the desired cure quality and stability properties
Solution Approach 2:
The carboxylic acid component acts as an intermediary that modifies the accelerator's function, enabling it to catalyze the anhydride-epoxy reaction more effectively at lower temperatures, thus mediating between the accelerator and the resin system
2Temperature
If conventional anhydride curing systems are used, then high temperature stability is achieved, but processing time is extended
Solution Approach 1:
The patent modifies the chemical parameters of the curing system through the carboxylic acid-modified accelerator, which increases the reaction rate and enables complete curing in less than 2 hours at 100°C, significantly reducing processing time while maintaining temperature stability
Solution Approach 2:
The curing system achieves dynamic optimization by using the carboxylic acid-modified accelerator to control the reaction kinetics, allowing the system to complete curing rapidly at lower temperatures without sacrificing the final temperature stability of the cured resin
3Productivity
If higher loading of accelerators is used, then cure speed is improved, but storage stability deteriorates due to gelation
Solution Approach 1:
The patent creates a composite accelerator system combining tertiary amine or imidazole with carboxylic acid, where the carboxylic acid component prevents gelation and improves storage stability while the amine/imidazole provides catalytic activity for fast curing
Solution Approach 2:
The carboxylic acid acts as an intermediary that prevents direct interaction between the accelerator and anhydride that would cause gelation, thereby enabling higher accelerator loadings for faster curing while maintaining storage stability
4Reliability
If conventional epoxy to anhydride ratio is used, then complete reaction is achieved, but material cost and processing complexity increase
Solution Approach 1:
The patent changes the stoichiometric parameters by using a lower anhydride to epoxy ratio (0.4-0.6), which is made effective by the enhanced catalytic activity of the carboxylic acid-modified accelerator, ensuring complete cure while simplifying formulation
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 system achieves full cure at lower temperatures, improving storage stability, reducing cycle time, and enhancing the mechanical and chemical properties of the cured products, making them suitable for applications in hot and wet environments while minimizing material waste and energy use.
Implementation Method 1
uses a higher loading of a hindered latent tertiary amine or an imidazole in combination with a carboxylic acid... With this formulated system a full cure can be achieved in less than 2 h at a significantly lower temperature (~100°C)
Data Source
Figure 1
AI summary
A curing agent composition comprising anhydride and approximately equimolar amount of tertiary amine or imidazole and carboxylic acid, the amine being 1-piperidinylethanol (N-hydroxyethyl-piperidine, NHEP) represented by the structure below or an imidazole represented by the structure below: (I) where R1 = H, a C1 -C20 straight chain or branched alkyl, or a monocyclic aryl; R2 = a C1 -C20 straight chain or branched alkyl, or a monocyclic aryl. The carboxylic acid is represented by RCOOH; R = a C1 -C20 straight chain or branched alkyl, or a monocyclic aryl. The composition comprises a lower ratio of epoxy resin to anhydride (1:0.4-0.6) than typically used (1:0.8-1.1). In addition, it uses a higher loading of the hindered latent tertiary amine or the imidazole in combination with the carboxylic acid (wt% ratio of combined amine and carboxylic acid to anhydride ~10%). With this composition a full cure can be achieved in less than 2 hr at a significantly lower temperature (~100°C).