Semisolid Epoxy Resin Fast Cure via Fine Curative Particles
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fast cure epoxy resin systems for fibre reinforced structures face challenges such as lengthy cure cycles, exothermic reactions leading to excessive temperatures, and the need for complex formulations or solvents, which can result in environmental issues and reduced shelf-life of prepregs.
Innovation Solution
A semisolid epoxy resin composition with a curative system where at least 90% of particles are below 25 µm in size, combined with a toughener like nitrile rubber, allowing for rapid curing without solvents and simple mixing, enabling 95% cure in under 10 minutes at 120°C or 6 minutes at 130°C, and maintaining handleability and shelf-life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a more reactive resin is used to increase Tg, then the glass transition temperature is improved, but the exothermic heat released during curing increases
Solution Approach 1:
The patent changes the particle size parameter of the curative from conventional larger sizes to below 25 μm (with at least 90% of particles below this size). This parameter change enables faster dissolution and more uniform distribution in the resin, achieving rapid curing (95% cure in under 10 minutes at 120°C) with reduced exothermic peak temperature while maintaining high final Tg above 80°C
Solution Approach 2:
The curative is pre-ground to fine particles below 25 μm before mixing with the resin. This preliminary size reduction action ensures rapid dissolution and uniform distribution during mixing, enabling controlled fast curing without excessive exotherm, while achieving high Tg through the selected curative-resin combination
2Loss of time
If curing agents and accelerators are included to speed up cure cycle, then the cure time is reduced, but the exothermic reaction increases
Solution Approach 1:
The patent changes the particle size parameter of the curative to below 25 μm, which fundamentally alters the dissolution kinetics. This enables rapid curing (95% in under 10 minutes at 120°C) without requiring high concentrations of accelerators, thus achieving fast cure cycle with controlled exotherm by relying on particle size-driven dissolution rather than accelerator-driven reactivity
3Ease of operation
If solvents are used in epoxy resin formulations, then the resin viscosity is reduced and handleability is improved, but environmental damage and disposal issues arise
Solution Approach 1:
The patent extracts and eliminates solvents from the epoxy resin formulation entirely. The solvent-free composition achieves appropriate viscosity and handleability through the specific combination of semisolid epoxy resin and fine particle curative, without requiring any solvent additives, thus eliminating environmental disposal issues while maintaining workability
4Speed
If pre-reaction of resin is performed to speed up cure, then the cure rate is improved, but shelf-life and handleability are reduced
Solution Approach 1:
The patent applies preliminary action to the curative (grinding to fine particles below 25 μm) rather than to the resin (pre-reaction). This distinction is crucial: pre-grinding the curative enables fast cure upon mixing without initiating premature resin curing, thus maintaining shelf-life and handleability of the prepreg while achieving rapid cure rate when activated
Solution Approach 2:
The patent segments the curing system into two separate components: the semisolid epoxy resin and the fine particle curative. This segmentation allows the curative to be pre-processed (ground to fine particles) without affecting the resin stability. The components remain separate during storage, preserving shelf-life, but react rapidly when mixed, achieving fast cure rate
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 provides a rapid, solvent-free, and cost-effective curing process for prepregs with improved handleability and shelf-life, achieving high mechanical properties and uniformity, suitable for applications like sporting goods, while minimizing exothermic risks and environmental impact.
Implementation Method 1
The curative has a particle size such that at least 90% of the particles have a size below 25 μm at ambient temperature of 21°C
Implementation Method 2
the curing reaction itself can be highly exothermic and this needs to be taken into account in the time/temperature curing cycle
Data Source
AI summary
Fast cure resin system comprise semisolid epoxy resins and finely divided curatives of particle size less than 25 microns. The resins are dry to the touch, can be readily combined with fibrous reinforcement to provide prepregs which can be rapidly cured in a short moulding cycle.