Reversible Elastomer Crosslinking via Boronic Ester Metathesis
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Solution Overview
Problem
Existing methods for recycling vulcanized rubber do not effectively address crosslinked elastomers and lack the ability to easily decrosslink and recrosslink, with devulcanization techniques being energy-inefficient and other decomposition methods failing to consider non-vulcanization crosslinked rubbers.
Innovation Solution
A method involving the use of an elastomer with a monoboronic acid ester-containing functional group, crosslinked and decrosslinked through contact with a diboronic acid compound in specific solvents with SP values between 10 and 13 (cal/cm3)1/2, allowing for reversible crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If devulcanization is used to recycle vulcanized rubber, then rubber content can be recovered, but energy efficiency is poor due to extremely high temperature required
Solution Approach 1:
The invention changes the chemical parameters of the crosslinking system by introducing boronic ester groups that undergo metathesis reactions at low temperatures. This replaces traditional high-temperature sulfur vulcanization with a system that can be decrosslinked at much lower temperatures, directly resolving the energy efficiency problem while maintaining rubber recovery capability
Solution Approach 2:
The boronic ester functional groups act as intermediary chemical structures that enable reversible crosslinking. These groups form dynamic covalent bonds that can be easily broken and reformed under mild conditions, serving as a mediator between the rubber polymer chains and enabling low-temperature decrosslinking and recrosslinking cycles
2Adaptability or versatility
If traditional decomposition methods are used for vulcanized rubber, then decomposition can occur at low temperature, but the method does not consider rubbers crosslinked by methods other than vulcanization
Solution Approach 1:
The invention creates a universal crosslinking system based on boronic ester metathesis that can be applied to various elastomer types regardless of their original crosslinking method. The boronic ester groups can be grafted onto different polymer backbones, making the decrosslinking method universally applicable to vulcanized rubber, crosslinked elastomers, and other polymer systems
Solution Approach 2:
The invention changes the chemical composition parameters by incorporating boronic ester functional groups into the elastomer structure. This chemical modification enables the material to undergo controlled metathesis reactions at low temperatures, making the decomposition method universally applicable across different elastomer types while maintaining low temperature operation
3Strength
If crosslinked elastomers are used, then material strength and stability are improved, but the ability to easily decrosslink and recrosslink is lost
Solution Approach 1:
The invention introduces dynamic covalent chemistry through boronic ester metathesis reactions. The crosslinks are not static but dynamically exchangeable, allowing the network to rearrange and reform. This dynamic character enables the crosslinked structure to be easily decrosslinked and recrosslinked multiple times while maintaining structural integrity and strength
Solution Approach 2:
The boronic ester groups serve as intermediary dynamic bonds within the crosslinked network. These intermediary bonds provide the mechanism for reversible crosslinking, allowing the elastomer to transition between crosslinked and uncrosslinked states easily while maintaining the strength and stability of the crosslinked structure during use
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 easy crosslinking and decrosslinking of elastomers, facilitating repeated cycles of decrosslinking and recrosslinking with maintained elastomer structure, enhancing material utilization and efficiency.
Implementation Method 1
PTL 2 discloses a method of crosslinking a polymer comprising boronic ester by addition of a functional additive carrying at least two boronic ester groups enabling the formation of a crosslinked network by boronic ester metathesis reaction
Data Source
AI summary
Provided is a method of crosslinking an elastomer that uses an elastomer that can easily be crosslinked and decrosslinked. The method of crosslinking an elastomer includes a step of causing contact of an elastomer including a monoboronic acid ester-containing functional group represented by a specific general formula (4) with a diboronic acid compound in the presence of a solvent. The solvent has an SP value of not less than 10 (cal/cm3)1/2 and not more than 13 (cal/cm3)1/2 and includes at least a single solvent having an SP value of not less than 8 (cal/cm3)1/2 and not more than 10 (cal/cm3)1/2.