Impact of Raster Angle on 3D Printing of Poly(Lactic Acid)/Thermoplastic Polyurethane Blends: Effects on Mechanical and Shape Memory Properties

Abstract

In this study, a 60:40 blend of poly(lactic acid) and thermoplastic polyurethane (PLA/TPU) is fabricated using fused material extrusion. The morphological, thermal, mechanical and thermoresponsive cyclic shape memory effect (SME) characteristics of 3D-printed specimens at various raster angles are investigated. This work introduces the innovative utilization of TPU's fibrillar alignment within a PLA matrix to achieve enhanced mechanical anisotropy and consistent shape memory performance. Morphological analysis reveals excellent printability, with the immiscible TPU phase forming submicron-diameter fibrils (≈0.78 ± µm) within the PLA matrix, leading to significant improvements in toughness and elongation at break when aligned with the printing direction and the load. Tensile test demonstrates anisotropy, with 0° raster specimens achieving a UTS of 16.1 ± 0.2 MPa and elongation at 305.5 ± 71.9%, compared to 4.5 ± 0.6 MPa and 10.8 ± 1.5% at 90°. Notably, despite the mechanical anisotropy, shape fixity ratios exceeded 95% and recovery ratios between 91 and 95% were achieved across all raster angles, demonstrating robustness in thermomechanical properties. These findings offer valuable insights into the relationship between morphology, mechanical characteristics, and shape memory behavior of PLA/TPU blends fabricated using fused material extrusion, positioning the material as a strong candidate for biomedical applications requiring precise shape recovery performance.