3D printing of PLA-TPU with different component ratios: Fracture toughness, mechanical properties, and morphology

In this study, three PLA-TPU compounds were prepared by the melt mixing method and after the process of compounding, filament preparation, and 3D printing with Fused Deposition Modeling (FDM). The mechanical properties under compression, tensile, bending, shear modes, and fracture toughness were comprehensively and experimentally assessed. Also, for thermal analysis and microstructural evaluation, Dynamic Mechanical Thermal Analysis (DMTA) and Scanning Electron Microscopy (SEM) were used. The thermal analysis of the PLA-TPU compounds showed an increase and decrease in the loss and storage modulus with increasing PLA value, while all compounds had almost the same glass transition temperature. The results of mechanical tests showed that by raising the amount of PLA, the strength and formability increased and decreased, respectively in all loading modes. The UTS values for PLA50, PLA70, and PLA90 were achieved 27.27 MPa, 40.91 MPa, and 54.18 MPa, respectively. Also, the fracture toughness results were consistent with the mechanical properties. The PLA90 had 1.69 and 2.36 times higher fracture toughness than the PLA70 and PLA50 compounds, respectively. SEM images showed that with the increase in the amount of TPU, the voids caused by the printing and neck growth due to the incomplete integration of the inter and intralayer rasters rises, which is the reason for the decrease in strength and printability. The shear test results also confirmed the SEM images quantitatively and showed that the connection between the layers and density improves with increasing the amount of PLA.