3D-Printed Thermoset Biocomposites Based on Forest Residues by Delayed Extrusion of Cold Masterbatch (DECMA)

We developed a 3D-printing process based on thermoset biocomposites termed Delayed Extrusion of Cold Masterbatch (DECMA). DECMA is a processing method, based on controlling the degree of curing, that takes some responsibility of the 3D printing from materials and as such can be used to 3D print otherwise unprintable materials. First, a masterbatch was produced by mixing a bio-based resin (bioepoxy) and sawdust and lignin. This paste was partially cured at room temperature until reaching an apparent viscosity suitable for extrusion (≈10⁵ mPa·s at 1 s^-1). The system was next cooled (5-10 °C) to delay subsequent hardening prior to 3D printing. The printability of the biocomposite paste was systematically investigated and the merits of the delayed extrusion, via DECMA, were assessed. It was found that DECMA allowed the revalorization of sawdust and lignin via 3D printing, as direct printing led to failed prints. Our approach afforded cost-effective, shear-thinning dopes with a high bio-based content (58-71%). The bio-based 3D-printed materials demonstrated good machinability by computer numerical control (CNC). Overall, the benefits of the introduced DECMA method are shown for processing bio-based materials and for on-demand solidification during additive manufacturing.