A Comparative Study of the Physico-Mechanical Properties of Material Extrusion 3D-Printed and Injection Molded Wood-Polymeric Biocomposites

The present study evaluates the effect of material extrusion 3D-printing and injection moulding (IM) on the physico-mechanical properties of polylactic acid (PLA)-wood flour (WF) biocomposites. The effect of both WF, at high levels, and a plasticizer on physico-mechanical properties was systematically evaluated and reported. All formulations were compounded using a batch melt-compounder with WF concentrations of 10 to 40 wt% with and without polyethylene glycol (PEG, 5 and 10 wt%) as plasticizer to provide filaments with uniform diameter by using a simple single screw extruder. Filaments with different weight% of wood content up to as high as 40 wt% were prepared, extruded, and 3D-printed using a low-cost desktop fused deposition modelling (FDM) 3D printer without any nozzle clogging for the first time. All filaments, 3D-printed, and injection-moulded parts were analysed for their physico-chemical, thermal, and mechanical properties in order to highlight the difference between IM and 3D printing in producing wood-based biocomposites, along with the importance of 3D printing optimization. The mechanical results indicated that the IM specimens had higher tensile strength and modulus compared to 3D-printed samples. Meanwhile, increasing PEG reduced the tensile strength and modulus, due to external plasticization, with the IM composites being more obvious in property changes. Morphological analysis showed evidence of voids for both methods, but 3D-printed samples were more pronounced.