Sustainable Conversion of 3D-Printed Thermosets into Thermoplastics Using Methacrylic Anhydride as a Hydrolytic Cleavable Cross-Linker

Abstract

Vat photopolymerization (VPP)-based three-dimensional (3D) printing has been rapidly adopted by various industries, but challenges arise when attempting to print thermoplastic polymers via VPP due to mechanical and resolution limitations. Therefore, multifunctional oligomers or cross-linkers are commonly used, creating strong, rigid, and accurate prints, while printed thermosets impede recyclability due to difficulties in melting and reprocessing. To address this challenge, we propose here a sustainable conversion of the 3D-printed thermosets into processable thermoplastics by utilizing methacrylic anhydride (MAA) as a hydrolytic cleavable cross-linker. Our results show that the utilization of MAA can significantly enhance printing accuracy, mechanical performance, and thermostability of poly(isobornyl acrylate) on a VPP-based 3D printer. Importantly, the MAA cross-linker facilitates effective hydrolysis, transforming the printed thermosetting polymers into processable thermoplastics. Through systematic thermal, optical, and chemical analyses together with prototype fabrication demonstrations, we validate this sustainable conversion. Moreover, our results suggest that this sustainable conversion method shows no obvious compromise in mechanical performance, as observed in the prevailing dynamic bonding approaches. This highlights its potential as a more sustainable pathway for developing eco-friendly and mechanically robust materials for future 3D printing industry applications.