Thermoplastic Polyurethane degradation during LPBF: Assessment of powder reusability

Architectural lattice structures fabricated via LPBF offer a sustainable alternative to traditional foams in protective sports equipment, but powder reuse introduces degradation risks that could compromise the mechanical performance and process reliability. This presentation explores the thermal aging behavior of thermoplastic polyurethane (TPU 1301) powder in polymer laser powder bed fusion (LPBF), with a focus on its impact on the printed part quality and powder lifecycle management.
The study first characterizes the evolution of powder and part properties over multiple print cycles. The powder is analyzed using morphological, rheological, and thermal analyses, while part properties are assed using X-ray computed tomography, quasi-static and dynamic mechanical testing. After 6 print cycles without refreshment, key findings include a 33.7% drop in powder bulk density, a 47% increase in endothermic enthalpy and a 4.6% increase in melt viscosity. These changes translated directly into part performance: CT scans revealed a marginal rise in internal porosity, while mechanical testing showed a 12–18% reduction in tensile strength, a 10% decrease in compressive modulus, and an increased scatter in energy absorption characteristics. Orientation dependent defects such as warping and delamination were also observed, limiting the printability of certain geometries.

This work highlights the importance of multi modal characterization in understanding powder degradation and provides practical tools for improving refresh strategies, ensuring consistent part quality, and extending the usable life of TPU powders in LPBF. The results contribute to advancing both the reliability and sustainability of polymer additive manufacturing.