Intro Polycarbonate urethanes (PCUs) have promise in many biomedical applications due to their low stiffness, biocompatibility, and high strength. We sought to develop relationships between PCU structure and mechanical properties, including fatigue, for soft PCUs with varied hard to soft segment ratios processed via injection molding (IM) or 3D printing (FDM). Methods PCUs of three different hardnesses (75A, 85A, and 95A) were made into test samples via either IM or FDM. Materials were characterized and then tested in monotonic tension, compression, shear, and tensile fatigue. Results Increased hard segment content (HSC) increases stiffness and shear failure stress, and improves stress-based tensile fatigue despite minimal effects on tensile strength. Effects of HSC on failure strain, and strain-based fatigue, were influenced by interaction between phases and indicate a trade-off between material damping (due to hydrogen bonding) and strain tolerance. FDM samples matched or exceeded IM samples across the board and exhibited consistently higher tensile failure strain and an improvement in strain-based tensile fatigue (see Figures) which is attributed to differences in phase organization. DMA and DSC data suggest smaller and less developed hard domains in FDM samples, which allows greater chain mobility, despite samples being given adequate time for phase separation. Such success with FDM has not yet been demonstrated in literature, and is attributed to favorable printing parameters as well as the apparent insensitivity of PCU to a small percentage (&lt; 1%) of voids.

Fatigue of injection molded and 3D-printed polycarbonate urethane in solution

253rd National Meeting (2017)

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