Effect of <scp>TPU</scp> Type and Concentration on the Rheological, Mechanical, and <scp>3D</scp> Printing‐Related Properties of <scp>PLA</scp>/<scp>TPU</scp> Blends

ABSTRACT This study investigates the effects of thermoplastic polyurethane (TPU) grades with different hardness levels on the rheological, mechanical, and viscoelastic properties of polylactic acid (PLA) blends for 3D printing applications. Rheological analysis revealed that TPU (A60), a TPU grade with a Shore A hardness of 60, exhibited high compatibility with PLA's rigid segments, while TPU (A98), another TPU grade with a Shore A hardness of 98 showed poorer interfacial interaction, leading to phase separation. TPU (A80), a TPU grade with a Shore A hardness of 80, exhibited a compatible phase morphology, enhancing processability and maintaining compatibility within the polymer matrix. Dynamic mechanical analysis (DMA) results demonstrated that TPU (A60) significantly reduced PLA's glass transition temperature (Tg) (from ~59°C to ~35°C) and modulus, leading to excessive softening and printability issues. TPU (A80) maintained an optimal Tg (~54°C) and modulus balance, enhancing impact resistance while maintaining structural compatibility. TPU (A98), with higher modulus values, exhibited limited adhesion, reducing its overall effectiveness in impact resistance enhancement. From a 3D printing perspective, TPU (A60) improved flexibility but compromised dimensional accuracy, while TPU (A98) provided rigidity at the expense of interlayer adhesion. TPU (A80) emerged as the most suitable option, offering stable filament extrusion, enhanced viscosity control, and improved interlayer bonding.