Preparation of polylactic acid (PLA)/thermoplastic polyurethane (TPU) composite filaments for FDM 3D printing: thermal, rheological, and mechanical characterization

Abstract

Polylactic acid (PLA) is widely used in fused deposition modeling (FDM) for its printability and biodegradability, yet its brittleness restricts engineering applications. This study incorporated thermoplastic polyurethane (TPU, 10–50 wt%) to fabricate PLA/TPU composites via melt blending, followed by the preparation of honeycomb-structured specimens. The influence of TPU content on thermal behavior, rheology, mechanical performance, and fracture morphology was systematically investigated. Results indicated that TPU suppressed PLA crystallization, reducing its cold crystallization temperature, crystallization enthalpy, and melting enthalpy. Rheological analysis showed that the addition of 20–30 wt% TPU effectively reduced viscosity while preserving melt elasticity. The melt flow rate exhibited a decreasing trend with increasing TPU content. Notably, at 50 wt% TPU, toughness and elongation at break increased by 571.7 % and 575.6 %, respectively, albeit with concomitant decrease in tensile strength. Furthermore, an L ₉ (3 ⁴ ) orthogonal design optimized printing parameters (nozzle temperature, printing speed, layer height, and infill density) for PLA/TPU (50/50) honeycomb structures. The optimal parameters were identified as a nozzle temperature of 210 °C, printing speed of 60 mm/s, layer height of 0.25 mm, and infill density of 75 %. These findings provide a theoretical basis for the additive manufacturing of high-performance, impact-resistant PLA honeycomb components.