Universal Dynamic Crosslinkers for Reprocessable Immiscible Plastics
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Solution Overview
Problem
There is no effective closed-loop solution for recycling mixed plastics, particularly polar/apolar polymer mixtures, as they are typically incompatible and phase separate, leading to materials with inferior properties.
Innovation Solution
Introduce a compatibilization strategy using dynamically forming graft multiblock copolymers by incorporating specifically designed universal dynamic crosslinkers into immiscible polymer mixtures, forming in-situ dynamic thermosets that enhance tensile strength and creep resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If mixed plastics (polar/apolar polymer mixtures) are used, then material diversity and recycling potential are improved, but compatibility and mechanical properties deteriorate due to phase separation
Solution Approach 1:
The patent introduces dynamically crosslinking agents as intermediary substances that mediate between incompatible polar and apolar polymer phases. These crosslinking agents form dynamic crosslinks at the phase interfaces, creating a compatibilized structure that maintains both phase separation for property retention and interface reinforcement for mechanical integrity. The dynamic nature allows the crosslinks to form and break, enabling reprocessing while maintaining compatibility.
Solution Approach 2:
The patent creates composite materials by combining multiple polymer types (polar and apolar) with dynamically crosslinking agents. The resulting material system integrates the beneficial properties of different polymers while using the crosslinking agent to bridge the incompatibility gap. The dynamic crosslinks form a network that holds the composite structure together, enabling the mixture to function as a coherent material with improved mechanical properties.
2Strength
If static crosslinking is used to improve mechanical properties, then strength and stability are improved, but reprocessability and recyclability deteriorate
Solution Approach 1:
The patent replaces static crosslinks with dynamic crosslinks that can form, break, and reform under different conditions. The dynamic crosslinking agents incorporate reversible bonds that maintain mechanical strength during service conditions but can be disrupted under reprocessing conditions (such as elevated temperature), allowing the material to be reprocessed and recycled. This dynamic behavior enables the material to transition between a crosslinked thermoset state for strength and a processable state for recycling.
3Productivity
If dynamic crosslinking is used to enable reprocessing, then recyclability is improved, but mechanical strength and structural stability may deteriorate
Solution Approach 1:
The patent utilizes parameter changes (temperature, pressure, time) to control the dynamic crosslinking equilibrium. At service temperatures, the crosslinks remain stable providing mechanical strength. During reprocessing at elevated temperatures, the dynamic crosslinks break and reform, enabling material flow and reshaping. The concentration and distribution of crosslinking agents are optimized to ensure sufficient crosslink density for strength while maintaining dynamic behavior for reprocessability.
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 resulting thermosets exhibit intrinsic reprocessability and enhanced mechanical properties, potentially providing a facile route for recycling mixed plastics while retaining their individual properties.
Implementation Method 1
Wulff et al. (Science 2019, 366, 875) is of universal static (permanent) crosslinkers (USCs) based on symmetric molecular bis(diazirine) precursors that, upon thermal or light activation, yield highly reactive bis(carbene) species that can crosslink seemingly any polymer bearing a C—H bond through inter-chain double C—H insertion of the carbene
Implementation Method 2
Leibler et al. (Science 2011, 334, 965) demonstrated that reversibly crosslinking a polymer to a vitrimer can yield a dynamic thermoset that can be repeatedly reprocessed while maintaining properties
Implementation Method 3
compatibilization ensures that the immiscible interface(s) between the distinct phases are reinforced by (macro) molecules that tie across them-surfactants are classic examples of such species
Data Source
AI summary
Described herein are compositions of matter for novel universal dynamic crosslinkers (UDCs) and the shortest closed-loop process for upcycling of any plastics, including post-consumer plastic waste and immiscible plastic mixtures enabled by UDCs. We discovered that the specifically designed UDCs can dynamically crosslink any plastics, and more importantly mixed immiscible plastics into compatibilized living grafted multiblock copolymers. Our studies show that such UDCs can reactivate mixed plastic dead chains and dynamically crosslink them into compatibilized multiblock copolymers. The in situ generated dynamic thermosets exhibit intrinsic reprocessability as well as enhanced tensile strength and creep resistance, relative to virgin plastics. This approach avoids the need for de/reconstruction and thus provides the maximum recovery of the endowed energy and materials value of the individual plastics.