The global plastic waste crisis is intensified by the challenge of upcycling mixed polymer streams, especially the incompatible phases of polyethylene and polypropylene. Here, we present a strategy to address this issue by converting post-consumer recycled polypropylene into a re-processable thermoset with adaptable chemical bonds. By cross-linking modified polypropylene with a tetrafunctional epoxy, we create a material that improves the properties of mixed plastic waste. Characterization through rheology, gel content analysis, and microscopy confirms the formation of a robust adaptable network, which provides superior mechanical properties, including high tensile strength and improved dimensional stability under deformation. These vitrimeric blends maintain their structure and performance across multiple reprocessing cycles, demonstrating potential for closed-loop recycling. We further show their application in additive manufacturing through fused granulate fabrication, converting low-value waste into feedstock for three-dimensional printing. Finally, computational simulations clarify the molecular mechanisms underlying this compatibilization. Fabrication of a cross-linked, covalent vitrimeric network with controlled mechanical properties and optimal tensile strength is possible through upcycling of mixed plastic waste from milk packets characterized through rheology, gel content analysis, and scanning electron microscopy.
Dey et al. (2026) studied this question.