STTR Phase I: Advanced compatibilization for mixed plastic recycling

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The broader impact of this Small Business Innovation Research Phase I project is to promote increased recycling and to enable the upcycling of two of the most common polymers found in mixed waste streams: polyethylene (PE) and isotactic polypropylene (iPP). While plastic recycling can assist in mitigating the vast and continuously growing volume of plastic waste, mixed plastic streams—notably those with PE and iPP—introduce many challenges. These polymers are immiscible but of similar density, making them unsuitable for simple melt-blending yet difficult to separate. Although additives have been developed to overcome the immiscibility issue, these additives typically need to be added at high loadings and produce resins with poor mechanical properties. This project focuses on the development of advanced additives (compatibilizers) that can be introduced in low concentrations to produce PE/iPP resins with superior durability, ductility, and industrial utility that rivals or outperforms homopolymers. Such a technology has the potential to bring superior efficiency to the mixed recycling process, advancing the field toward a more circular plastics economy. By delivering high-value products from waste streams, widespread adoption of this technology would drive improvements in plastic waste collection, recycling, and re-manufacturing, supporting jobs in these and adjacent fields.This project involves the creation of non-reactive, multi-graft copolymers capable of supporting high-quality iPP/PE blends with superior tensile strength characteristics, impact resistance, and rigidity compared to current resins. The proposed approach leverages interlocked molecular entanglements and co-crystallization to provide stronger adhesion to iPP and PE. This technology seeks capability of up to 30% iPP contamination in PE using as little as 1 wt% additive to generate high-value blended materials. Phase I development will involve: 1) optimization of polyethylene-graft-iPP copolymer compatibilization additives, 2) scale-up of optimized polyethylene-graft-iPP copolymers, 3) testing of larger scale batches for end polymer qualities, and 4) testing of compatibilizers with combinations of different grades of actual post-consumer plastic waste. The technology may contribute to an enhanced understanding of how specific copolymer architectures influence compatibilization efficiency, while also meeting the need for technologies to support compatibilization of PE and iPP for blended recycling applications.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.