Additive manufacturing of wood flour/polyhydroxyalkanoates (PHA) fully bio-based composites based on micro-screw extrusion system

Abstract

Crystalline bio-based composites exhibit discontinuous feeding and warpage of printed parts in traditional filament printing. Therefore, an additive manufacturing (AM) system based on micro-screw extrusion was designed, and wood flour/polyhydroxyalkanoates (WF/PHA) composites without additives were manufactured. The differential scanning calorimetry test showed that the crystallization temperature and melting temperature of the WF/PHA composites increased by 35.7 °C and 46.1 °C, respectively. The evaluation of the extrusion stability of the micro-screw extrusion system showed that the micro-screw speed had a greater influence on extrusion output than the printing temperature. The forming process under pressure and the WF/PHA blend prevented the warpage of printed samples. The tensile and flexural strengths of the WF/PHA composites reached 38.7 MPa and 77.3 MPa, respectively, and the modulus of the WF/PHA composites significantly improved with the increase in WF content. The rheological, thermal, and mechanical properties of the printed samples were used to determine the reason for the decrease in warpage. Finally, the test printing of thin and large-area sheets provides the conditions for the application of AM in fully bio-based composites.