Cyclic Economy-Driven Composites for Material Extrusion Three-Dimensional Printing: Poly(methyl methacrylate) from Recycled Scrap with Optimized Biomass-Derived Biochar Filler Content.

Environmentally friendly materials are emerging materials that find applications in an increasing number of cases when being three-dimensional printed (3D-P), as they can provide many possibilities and offer unique properties to fulfill industrial needs and requirements. As part of that effort, recycled (from sheet trimmings waste) poly-(methyl methacrylate) (PMMA) and (nature-sourced) biochar were selected to be combined and examined herein. Composites with Biochar concentration in the 0.0-10.0 wt % (step 2.0 wt %) range were assessed. Compounds were extruded into filaments, which fabricated coupons (material extrusion 3D-P) for the tests that followed. The samples were experimentally evaluated for their characteristics related to mechanical, chemical, rheological, and thermal behavior, as well as for their structure and morphology. Mechanical testing included tensile, bending, and Charpy Notched coupons' investigation. The microhardness was also measured. In addition, quality characteristics were assessed through porosity and dimensional deviation data analysis. The composite distinguished in relation to pure PMMA was PMMA/Biochar 6.0 wt % (>20% increase in the strength on the tensile and flexural experiment), as most of the investigated properties revealed their greatest values in that Biochar concentration. Furthermore, the eco-friendly biochar addition positively affected most of the recycled PMMA characterization metrics assessed, showing potential for the environmentally friendly composites developed herein for the 3D-P process.