A recyclable, reshapable and UV-curable polybenzoxazine vitrimer enabling closed-loop 3D printing applications

Abstract

The additive manufacturing of a bio-based, UV active, recyclable and reshapable polybenzoxazine is demonstrated. A new ditelechelic benzoxazine monomer (CHDM-PA-mea) was prepared by esterification of phloretic acid (PA) and cyclohexane dimethanol (CHDM)-both chosen for sustainability-and then reacting the product with monoethanolamine (mea) and paraformaldehyde (PFA). This yielded a molecule with two benzoxazine rings, two ester groups and two aliphatic hydroxyls. UV-curability was obtained through partial acylation of the aliphatic hydroxyls to form methacrylates. The modified benzoxazine monomer was then 3D printed via UV-assisted materials extrusion, with thermal post-treatment yielding complex parts composed of a fully cured polybenzoxazine vitrimer. The influence of the degree of methacrylation on vitrimer characteristics was explored with the aim of balancing photopolymerisation and printability with vitrimeric properties, as assessed by reshaping and recycling abilities. This work identifies an optimal benzoxazine precursor enabling the production of complex 3D printed vitrimer parts that can be reshaped and recycled, with a T_α of 105 °C, a compressive modulus of 810 MPa and excellent dimensional stability. Ground 3D printed parts were used as viscosity modifiers for new prints, closing the successful recycling loop for this material.