Poly(Urea-Urethane) HUB Recycling for Reprocessable Composites
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Solution Overview
Problem
There is a need for polymeric materials with desired in-use performance characteristics that are malleable, repairable, and shape reprogrammable, and for recycling methods that can degrade or reversibly depolymerize these materials, particularly for composite materials like glass fiber reinforced plastics (GFRP) that are difficult to recycle due to their thermoset nature.
Innovation Solution
A process for recycling poly(urea-urethane) polymers by treating them under conditions to partially cleave urea bonds, forming a mixture of prepolymers, which can be reshaped or repaired, using dynamic hindered urea bonds (HUBs) that act as covalent adaptable networks (CANs), allowing for thermo-mechanical processing and recovery of valuable materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermosets are used to provide dimensional stability and chemical resistance, then mechanical performance and stability are improved, but recyclability and reprocessability deteriorate
Solution Approach 1:
The patent applies dynamic covalent chemistry by incorporating reversible imine bonds and disulfide bonds into the polymer network. These dynamic bonds allow the thermoset to undergo bond exchange reactions under specific conditions (pH, temperature), enabling the material to transition from a rigid, non-reprocessable state to a flexible, reprocessable state. This resolves the contradiction by making the previously static network dynamically adaptable.
Solution Approach 2:
The patent changes the chemical parameters of the polymer network by introducing functional groups that can undergo reversible reactions. The imine bonds can form and break under different pH conditions, and disulfide bonds can exchange under specific temperature and catalytic conditions. These parameter changes enable the material to switch between stable and reprocessable states, simultaneously achieving reliability and recyclability.
2Strength
If thermoset polymers are used to achieve excellent mechanical performance, then strength and stability are improved, but adaptability and reshaping capability deteriorate
Solution Approach 1:
The patent introduces dynamic covalent bonds (imine and disulfide) that can reversibly break and reform under specific conditions. This dynamic behavior allows the material to maintain structural integrity during use (providing strength) while enabling reshaping and reprocessing when exposed to triggering conditions such as pH changes or temperature variations.
Solution Approach 2:
The patent employs periodic or triggered actions to initiate bond exchange reactions. By applying specific stimuli (pH changes, temperature cycles, catalytic agents) at appropriate times, the material can periodically transition between stable and reprocessable states, enabling controlled reshaping while maintaining overall structural performance.
3Strength
If poly(urea-urethane) polymers with hindered urea bonds are used to provide desired in-use performance, then mechanical characteristics are improved, but degradability and depolymerization capability deteriorate
Solution Approach 1:
The patent changes the chemical environment parameters (pH, temperature, presence of catalysts) to trigger the depolymerization of hindered urea bonds. Under specific conditions such as acidic or basic environments, the urea bonds undergo hydrolysis or exchange reactions that break down the polymer network, enabling controlled degradation and depolymerization while maintaining mechanical performance under normal use conditions.
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 process enables the recovery and reuse of poly(urea-urethane) polymers and fillers like carbon fibers, facilitating easy repairability and recyclability, while reducing waste and carbon footprint, and providing materials suitable for various applications.
Implementation Method 1
treatment of the composition comprising the poly(urea-urethane) polymer under conditions suitable to at least partially cleave the urea bonds of the polymer
Implementation Method 2
urea bonds bearing a bulky group on the nitrogen atom resulted in hindered urea bonds (HUBs) that were dynamic and can reversibly dissociate into an amine and isocyanate based on the associative exchange mechanisms
Data Source
AI summary
The present invention relates to a process for recycling a composition comprising a poly(urea-urethane) polymer with hindered urea bonds comprising the treatment of the composition comprising the poly(urea-urethane) polymer under conditions suitable to at least partially cleave the urea bonds of the polymer to give a mixture (M1) containing prepolymers. The present invention also relates to the prepolymer obtained or obtainable according to the process, a poly(urea-urethane) polymer obtained or obtainable according to the process according to the present invention as well as the use of said prepolymer for the preparation of a poly(urea-urethane) polymer.