Cleavable Free-Radical Composite for Recyclable Crosslinked Resins
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Solution Overview
Problem
Existing free-radical curable resin composites with tightly crosslinked networks are difficult to recycle due to high crosslinking density, limiting their recyclability and sustainability.
Innovation Solution
A composite comprising a cured free-radical curable composition that is cleavable in specific environments, such as aqueous liquids, alcohols, and acids at elevated temperatures, allowing for the recovery of fillers like glass and carbon fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If free-radical curable resins with tightly crosslinked networks are used to achieve excellent mechanical and chemical resistance, then the mechanical strength and chemical resistance are improved, but the recyclability and ease of de-crosslinking deteriorate due to high crosslinking density
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by using cleavable crosslinkers with specific functional groups (oxime, hydrazone, semicarbazone, thiosemicarbazone, or hydrazone) that can be broken down under specific conditions. This allows the cured resin to maintain strong crosslinking during service but become de-crosslinkable during recycling, resolving the contradiction between mechanical strength and recyclability
Solution Approach 2:
The patent extracts the permanence characteristic from the crosslinked network by incorporating cleavable bonds that can be selectively broken. The crosslinking structure is taken out as a temporary state that can be reversed, allowing the resin to transition from a permanently cured state to a recyclable state through de-crosslinking processes
2Reliability
If high crosslinking density is achieved to improve chemical resistance, then the chemical resistance is improved, but the difficulty of de-crosslinking and filler recovery increases
Solution Approach 1:
The patent introduces intermediary cleavable bonds (oxime, hydrazone, semicarbazone, thiosemicarbazone, or hydrazone groups) within the crosslinking structure that act as weak points susceptible to specific chemical or physical stimuli. These intermediary bonds allow the robust crosslinked network to be selectively broken down, facilitating de-crosslinking and filler recovery while maintaining chemical resistance during service
3Ease of manufacture
If cleavable crosslinking polymers are used to improve recyclability, then the recyclability is improved, but the mechanical and chemical resistance may deteriorate due to lower crosslinking density
Solution Approach 1:
The patent applies local quality by placing cleavable functional groups (oxime, hydrazone, semicarbazone, thiosemicarbazone, or hydrazone) at specific locations within the crosslinking structure while maintaining overall high crosslinking density. This localized cleavability allows the majority of the network to remain intact and provide mechanical strength, while specific points can be broken to enable 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
The composition maintains mechanical and chemical resistance during its service life while enabling effective recyclability through cleavage, facilitating the recovery of valuable materials.
Implementation Method 1
free-radical curable resins are used in the production of glass fiber and carbon fiber composites. While cured composites based on free-radical polymerizable groups have excellent mechanical and chemical resistance due to their tightly crosslinked network
Implementation Method 2
the cured free-radical curable composition that is cleavable wherein the uncured free-radical curable composition comprises... a cured free-radical curable composition which is cleavable... subjecting the cured free-radical curable composition to a cleaving environment
Data Source
AI summary
A composite comprising a filler and a free-radical curable composition that is cleavable after being cured, comprising at least one crosslinker molecule component a. of general formula E1-O—C(R2)(R3)—X-E2 (1), wherein each of E1 and E2 comprises an ethylenically unsaturated free-radical polymerizable moiety, X is either oxygen (O) or sulphur (S), and optionally, at least one ethylenically unsaturated free-radical polymerizable molecule component b, not comprising the moiety —O—C(R2)(R3)—X—, wherein in case the composition is cured, the composition forms a polymer having a Tg of more than 50° C. as measured by dynamic mechanical thermal analysis (DMTA).