Influence of biobased plasticizers on 3D printed polylactic acid composites filled with sustainable biofiller

Abstract

Three-dimensional (3D) printing is extensively explored in scientific research and engineering applications; however, little is known about the feasibility of 3D printing multi-material composites. This paper investigates the effect of three different plasticizers including epoxidized soybean oil (ESO), polyethylene glycol (PEG), and glycerol on mechanical and thermal properties of PLA filled with distillers dried grains with solubles (DDGS) filaments for 3D printing. The composite filaments were extruded using a twin-screw extruder equipped with a collector to achieve uniform diameter. The eco-friendly PLA-DDGS-plasticizer based filaments were then used to print dog-bone and flexural samples. The results showed that the PLA-DDGS blends plasticized with ESO have improved elongation at break compared to pure PLA and those plasticized with glycerol and PEG. These results were evidenced by SEM micrographs showing PLA-plasticizers phase separations and formation of voids in fracture surface of PLA-DDGS plasticized by PEG and glycerol. DMA and FT-IR measurements confirmed the compatibility between PLA and ESO. PLA-DDGS blend containing 10 % ESO exhibited 6 % higher storage modulus in comparison with PLA samples, while the addition of 12.5 % ESO reduced storage modulus by 27 %. Storage modulus in 3D printed samples plasticized by PEG and glycerol showed a reduction of 32 % and 89 %, respectively. The same trend was observed in the mechanical properties of 3D printed composite filaments. Among all samples, PLA-DDGS blends plasticized by 15 % ESO exhibited higher elongation at the break while a significant reduction of 21 % was observed in ultimate tensile strength. The study confirmed that the types and amounts of plasticizer dictates the morphology and mechanical properties of PLA-DDGS composite.