Processing–structure–property relationships and post-print conditioning effects in TPU/ZnO nanocomposites for fused deposition modeling

초록

Fused deposition modeling (FDM) is widely used for rigid and flexible polymers; however, printable materials that combine high strength with flexibility remain limited. This study systematically investigates processing–structure–property relationships and post-print conditioning behavior of a thermoplastic polyurethane (TPU) nanocomposite reinforced with 5 wt% zinc oxide (ZnO) nanoparticles for FDM. Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and thermal analyses confirmed that ZnO was physically blended into the TPU matrix without chemical alteration, achieving uniform filler dispersion, dense filament morphology, and processing stability within the FDM temperature window. Direct comparison with neat TPU confirmed that ZnO addition improved compressive strength by 109% (p < 0.001) while reducing the minimum printable nozzle temperature by 25–30 °C. Importantly, compressive strength progressively increased by approximately 50% over the first 14 days after printing and then plateaued, revealing a time-dependent stabilization phenomenon often overlooked in elastomeric FDM materials. Two-way ANOVA confirmed nozzle temperature as the dominant parameter (p = 0.0011), with a significant temperature–speed interaction (p = 0.009). Cyclic compression showed 3–6% stress softening, residual strain below 6%, and energy dissipation of 0.86–1.06 MJ m⁻³ , demonstrating excellent elastic recovery and viscoelastic damping. Furthermore, higher nozzle temperatures increased interlayer bonding, thereby increasing strength and energy absorption. The results demonstrate that TPU–ZnO composites offer significant potential for flexible load-bearing and energy-absorbing applications.

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