Simultaneous reinforcement and toughening of polymer/hydroxyapatite composites by constructing bone-like structure

Inspired by the hierarchically ordered structure of natural bones with the integration of outstanding strength and toughness, we made an endeavor to engineer ultra high molecular weight polyethylene (UHMWPE)/hydroxyapatite (HA) biocomposites with bone-like structure. The gradiently oriented architecture is constructed via ingenious control over the flow field during the injection molding. In the outer layer, intense shear induces a plenty of highly oriented UHMWPE lamellae, which mimic the aligned collagen fibers in the natural bone. In the inner layer, chain relaxation gives rise to relatively disordered lamellae, contributing to a tough core that shares the similarity with the soft internal layer of natural bones. Such a unique spatial architecture remarkably strengthens the mechanical performance of structured UHMWPE/HA biocomposites. Strikingly, tensile strength and impact toughness are significantly increased by 170% and 85%, climbing up to 63.4 MPa and 103.9 kJ/m2, respectively, which is hardly achieved in the previous studies. Meanwhile, structured UHMWPE/HA exhibits good biocompatibility and bioactivity. Our work offers an efficient, time-saving and scalable approach to fabricate high performance UHMWPE/HA biocomposites, where the simultaneous enhancement of strength and toughness makes the structured UHMWPE/HA a promising candidate of replacements for cortical bones.