Bio-based polymer composites obtained by vat photopolymerization of photocurable resins modified with biochar as sustainable filler

• Biochar-based polymer composites were prepared via LCD vat-photopolymerization. • 3D printed objects with very complex structures and high level of definition were realized by adding biochar to an AESO photocurable resin. • Thermal, morphological, and mechanical properties were extensively studied together with cell viability and cytocompatibility. The present work focuses on the preparation and characterization of novel bio-based photocured composites realized by vat photopolymerization (VP) 3D printing. Acrylate epoxidized soybean oil (AESO) resin was selected as the monomeric starting material and mixed with isobornyl methacrylate (IBOMA), used as reactive diluent at 50 wt%, in the presence of phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), as radical photoinitiator. The polymerization process was carried out by using a VP technology as the liquid crystal display (LCD) 3D printing. Biochar (BC), deriving from biomass pyrolysis, was added to the resin from 0.5 up to 2 wt% to obtain the final bio-based composites formulations. Rheological measurements were firstly performed to evaluate the viscosity and the printability of the photocurable formulations, and photo-DSC analysis was carried out to study the photo-curing phenomenon and the effects of the BC presence on the curing process within the 3D printer. After determining the optimal printing parameters, different geometries were printed, leading progressively to the realization of more complex parts with a high number of layers and good dimensional accuracy, such as alternative forearm splints prototypes for biomedical applications. The bio-based composites loaded with biochar underwent several characterization measurements to investigate their thermal, morphological, and mechanical properties. Finally, cell viability and cytocompatibility tests were carried out to study the real applications as bio-based materials for prosthesis development.