Comprehensive characterization of 3D-printed TPU/carbon black composites: Morphological, thermal, and mechanical properties

This study explores the impact of incorporating varying weight percentages of carbon black (CB) additive filler on the mechanical and microstructural properties of thermoplastic polyurethane polymer, a commonly used thermoplastic in 3D printing. Blends with distinct weight concentrations of CB (1 %, 3 %, 5 %, and 7 wt%) were prepared using the melt mixing method (Brabender internal mixer) and then 3D-printed via direct granule-based material pneumatic FDM machine. Printability, microstructure, thermal and mechanical properties were rigorously investigated. Thermogravimetric analysis (TGA) results revealed a notable shift in the initial decomposition phase to a higher temperature range and an increase in the melting transition temperature due to the presence of carbon black particles. Mechanical properties of the 3D printed samples were meticulously examined and compared with prior research. The blend samples containing 5 wt% CB exhibited significantly enhanced tensile strength, attributed to aligned short rigid urethane polymer chain reactions with CB. Samples with 5 wt% CB demonstrated superior mechanical properties compared to 7 wt% CB specimens, likely attributed to fewer potential failure points, as evidenced by Scanning Electron Microscope (SEM) analysis of fractured cross-sections of 3D-printed samples immersed in liquid nitrogen. Additionally, 3D-printed samples with combined infill orientations (0 degrees and 90 degrees) were generated and subjected to tensile strength testing. Microstructure analyses identified the piled-up agglomeration phenomenon, and the common 3D printing defects, known as void, responsible for failure modes in the 3D-printed samples.