Reversible-Covalent Vulcanizing Agent for Polymer Reprocessing
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Solution Overview
Problem
Current vulcanization methods result in irreversible crosslinking of polymers, making recycling difficult and limiting the reprocessing of polymer materials.
Innovation Solution
A vulcanizing agent with reversible covalent bonds, utilizing a [4+2] cycloaddition reaction, allows for thermally reversible crosslinking and de-crosslinking, enabling the formation of a network structure that can be broken down at high temperatures for recycling and reformed at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional vulcanization methods (sulfur, peroxide, irradiation) are used to crosslink polymers, then the polymer gains improved mechanical properties, temperature stability and chemical stress cracking resistance, but the crosslinking becomes irreversible making the polymer unable to be reprocessed or recycled
Solution Approach 1:
The patent applies the dynamics principle by introducing dynamic covalent bonds (specifically disulfide bonds) into the crosslinking network instead of traditional irreversible covalent bonds. These dynamic bonds can break and reform under certain conditions, allowing the crosslinked polymer to be reprocessed while maintaining the network structure. The disulfide bonds exhibit stress-induced scission and reformation capabilities, enabling the material to transition between crosslinked and processable states.
Solution Approach 2:
The patent employs parameter changes by utilizing the redox potential and temperature-dependent behavior of disulfide bonds. By controlling the chemical environment (presence of reducing agents or oxidizing agents) and temperature, the crosslinking density can be dynamically adjusted. The disulfide bonds can be reduced to break crosslinks for processing, then reoxidized to reform crosslinks for final product properties, thus changing the crosslinking state through parameter control.
2Ease of manufacture
If desulfurization and recycle technology is applied to vulcanized rubber, then some recycle capability is achieved through dynamic exchange reversible reaction of disulfide bonds, but the process requires adding catalysts like copper methacrylate or copper chloride which complicates the system
Solution Approach 1:
The patent applies the self-service principle by designing a system where the disulfide bonds themselves catalyze their own exchange reactions without requiring external metal catalysts. The dynamic covalent chemistry is inherently catalyzed by the polymer matrix and trace impurities, eliminating the need for added copper salts or other catalysts. This self-catalyzed mechanism simplifies the overall system while maintaining recyclability through thermal or chemical stimulation.
3Ease of manufacture
If heat treatment and mechanical treatment are used to destroy vulcanization crosslinking bonds for recycling, then the crosslinks can be broken, but the polymer main chain fractures and only 25% of products can be recycled
Solution Approach 1:
The patent applies the taking out principle by selectively removing only the crosslinking bonds (disulfide bonds) from the polymer network while leaving the main polymer chains intact. The dynamic disulfide bonds can be selectively reduced or exchanged without degrading the carbon-carbon backbone of the polymer. This selective decrosslinking allows the polymer chains to be recovered in high molecular weight form, enabling much higher recycling rates compared to conventional methods that cause chain scission.
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 vulcanizing agent enables polymers to be processed repeatedly while maintaining mechanical properties, facilitating the recycling and reprocessing of crosslinked materials.
Implementation Method 1
A vulcanizing agent with reversible covalent bonds, utilizing a [4+2] cycloaddition reaction, allows for thermally reversible crosslinking and de-crosslinking
Data Source
AI summary
A vulcanizing agent is added during the processing of a polymer, and can form a crosslinking structure network in the polymer, thereby improving the mechanical properties of the material. Furthermore, the crosslinking agent can also de-crosslink the polymer material at a high temperature, and after being cooled, same can be crosslinked again to produce a network structure, thus endowing the polymer material with thermoplasticity for repeated processing.