Study of the Thermal and Hydrothermal Aging Effects on the Properties of <scp>3D</scp> ‐Printed Thermoplastic Polyurethane

ABSTRACT In this study, the thermal and hydrothermal aging of TPU produced with the FDM technique was simulated and subjected to a series of tests. The alterations in the internal structures of the samples that had been subjected to tensile, hardness, adhesive wear tests, DSC, and optical microscopy analyses were examined. Mechanical tests revealed an increase in tensile strength, hardness, and elastic modulus in aged samples. Tribological tests showed an increase in the coefficient of friction in both types of aging, with the thermally aged sample exhibiting the highest value. DSC analyses revealed that hydrothermal aging led to an increase in crystallinity, while thermal aging resulted in a decrease in crystallinity despite an increase in rigidity in the amorphous regions. Microstructural analysis showed that the number of voids decreased and interlayer bonds strengthened after aging. The results obtained indicate that aging processes significantly affect the mechanical and tribological performance of TPU. In particular, hydrothermal aging causes a marked increase in modulus and crystallinity, while thermal aging has been the most influential method on hardness and coefficient of friction. The absence of mass loss in the samples during wear tests indicates that surface deformation remains limited with aging, suggesting that aging provides a more stable surface behavior. These findings highlight the necessity of optimizing aging conditions specifically for the application.