CAS-SC: Universal polymer compatibilization for recycling mixed plastic waste

NON-TECHNICAL SUMMARY: The main goal of this project is to find a practical and scalable way to recycle mixed plastic waste. Most plastics do not mix well, making it hard to recycle them using current methods. Traditional recycling methods are designed for specific types of plastics and do not work well for mixed plastic waste. Although there have been some new recycling techniques, none have successfully solved the problem of mixed plastic waste. To address this, two new methods will be investigated, both making use of a special type of chemistry that can form and break bonds easily. Method 1 will introduce chemical bridges between different plastic types while they are being melt processed together, facilitating them to stick together better. Method 2 will use pre-made materials that mechanically interlock different plastic molecules during melt processing. Both methods are designed to work with diverse type of plastics, making them potentially applicable for recycling various plastics together. If successful, this project could introduce a new universal strategy for recycling mixed plastics together, helping to reduce the global problem of plastic pollution. The proposed study will provide great opportunities to train graduate and undergraduate students, including minority and women students working on this project. TECHNICAL SUMMARY: The primary goal of this project is to develop a practical and scalable approach for the universal compatibilization of polymers, facilitating the recycling of mixed plastic waste. The inherent immiscibility of most plastics poses a significant challenge to mechanical recycling efforts. Traditional compatibilization methods, tailored to specific polymer compositions, are impractical for addressing mixed plastic waste. Despite the emergence of various innovative recycling methods, an effective solution for recycling mixed plastic waste remains elusive. To tackle this challenge, this project will investigate two innovative compatibilization methods, both based on dynamic covalent chemistry. In Aim 1, a robust dynamic covalent crosslinking chemistry will be developed to efficiently introduce dynamic crosslinks during melt extrusion, chemically connecting different polymer chains as in situ-formed compatibilizers. In Aim 2, pre-made vitrimers will be explored as compatibilizers for immiscible polymer blends, creating mechanical interlocks during melt extrusion. Both approaches share the distinctive feature of independence from specific polymer structures, potentially offering universal applicability for compatibilizing diverse plastics. This project aligns with the CAS-CS focus on “Developing enhanced methods for recycling and upcycling of chemicals and materials, especially as related to circular technologies”. If successful, the project could introduce a new, universal strategy for polymer compatibilization, addressing the global environmental challenge of plastic pollution through the recycling of mixed plastic waste. The proposed study will provide great opportunities to train graduate and undergraduate students, including minority and women students working on this project. . This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.