Abstract
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.
Highlights
Nozzles with a small diameter give an acceptable resolution in fused deposition modeling (FDM), they limit the capacity or processing throughput
In Delayed Extrusion of Cold Masterbatch (DECMA), the scope is to shift the burden from materials to the processing method, so otherwise unprintable materials can be used for 3D printing
The use of DECMA allows the printability of these residues
Summary
Nozzles with a small diameter give an acceptable resolution in fused deposition modeling (FDM), they limit the capacity or processing throughput. The incorporation of cellulose-based fillers has been reported to increase the Tg of polymers such as epoxies,[46] but this is not always the case.[47] The bioepoxy used in this study showed low tensile stress (Figure 4C) compared with other bioepoxies available in the literature, which have shown tensile strengths of up to 88 MPa.[48] The incorporation of fillers substantially changed the material’s mechanical behavior by decreasing the stress and strain at break. In other words, it made the material more brittle. Kumar et al.[49] reported a reinforcing effect in epoxies; the incorporation of 7.5% sawdust increased stress at breaking (from 10 to 22 MPa), which supports the hypothesis that the decrease in mechanical properties is due to the presence of bubbles
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