Acid-Labile Cross-Linking Agents for Reworkable Epoxy Resins
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Solution Overview
Problem
Epoxy-based materials are notoriously difficult to disassemble and recycle due to their highly cross-linked network, which makes them challenging to remove or rework without damaging the underlying structure, limiting their recyclability and reusability in various applications.
Innovation Solution
Development of epoxy resin compositions with acid-labile cross-linking agents, such as those described in Formulas I and II, which allow for the use of cleavable bonds in the hardener component, enabling controlled disassembly and degradation of the cured resin under specific conditions, including acidic environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy resin is cured with conventional cross-linking agents to form a highly cross-linked network, then mechanical strength and durability are improved, but reworkability and recyclability deteriorate
Solution Approach 1:
The patent changes the chemical parameter of the cross-linking agent by introducing acid-labile groups (acetal, ketal, orthoester, orthocarbonate) into the hardener structure. This allows the cured epoxy to maintain strong cross-linking under normal conditions while enabling controlled degradation when exposed to acidic environments, thus achieving both strength and reworkability
Solution Approach 2:
The patent extracts the permanent cross-linking function from the cross-linking agent by incorporating cleavable bonds that can be selectively removed under specific conditions. The acid-labile groups are taken out as removable components that break down under acidic conditions, allowing the epoxy network to be disassembled and recycled while maintaining structural integrity during service
2Reliability
If epoxy resin is cured to form an infusible three-dimensional network, then thermal stability and chemical resistance are improved, but removability and environmental sustainability deteriorate
Solution Approach 1:
The patent changes the chemical stability parameter of the cross-linking network by incorporating acid-responsive cleavable bonds. The epoxy maintains thermal stability and chemical resistance under normal service conditions, but can be selectively degraded under acidic conditions for environmentally friendly removal and recycling, reducing environmental harm
Solution Approach 2:
The patent converts the harmful environmental persistence of conventional epoxies into a beneficial feature by designing acid-labile cross-linking agents. The same chemical groups that provide structural integrity can be selectively broken down under acidic conditions, transforming the previously harmful permanent cross-linked network into a recyclable material system
3Ease of manufacture
If conventional polyamine hardeners are used for cold curing, then ease of processing and adhesion are improved, but bond permanence and resistance to removal increase excessively
Solution Approach 1:
The patent merges two previously separate functions into a single cross-linking agent: the cold-curing capability of polyamines and the controlled degradability of acid-labile groups. The resulting hybrid hardener maintains ease of processing and adhesion while enabling controlled bond breakdown, achieving both permanent bonding during service and removable bonding for recycling
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
Enables the creation of reworkable epoxy compositions that can be easily removed or recycled, maintaining mechanical and adhesive integrity, and expanding the use of epoxies in new markets by allowing for the disassembly of bonded items and the recovery of materials without damaging the underlying structure.
Implementation Method 1
enabling controlled disassembly and degradation of the cured resin under specific conditions, including acidic environments
Implementation Method 2
the epoxy resin reacts in the ambient with polyvalent nucleophiles such as polyamines to form a polymeric network of essentially infinite molecular weight
Data Source
AI summary
Compounds of formula I, uses as crosslinking agents or curing agents thereof, and resins obtained by using the compounds as crosslinking agents.