Solvent-Free Upcycling Vitrimers through Digital Light Processing-Based 3D Printing and Bond Exchange Reaction

Vitrimers, a type of dynamically crosslinked polymers that combine the solvent- and heat-resistance of thermosets with the reprocessability of thermoplastics, offer a new solution to the problem of plastic pollution. However, the current recycling approaches of vitrimers greatly constrain the shapes of recycled vitrimers to simple geometries, thus significantly limiting the application scopes of recycled vitrimers. Here, a simple but universal method for upcycling vitrimer wastes is reported by developing a UV curable recycling (UVR) solution system. Conventional unprintable vitrimer powders can be mixed with the UVR solution, and the resulting mixture is compatible with digital light processing based 3D printing to fabricate 3D structures with high resolution (up to 20 µm) and high geometric complexity. Heat treatment triggers bond exchange reactions in the printed structures, and greatly enhances the mechanical properties. This method allows to cyclically print vitrimer wastes multiple times. Moreover, the UVR-vitrimer mixture solution can work as an adhesive to bond printed small parts together to build a larger and more complex structure which cannot be printed. The upcycling method reported in this work extends the application scope of recycled vitrimers and provide a practical solution to address environmental challenges associated with plastic pollution.