title: Influence of the aspect ratio of bioactive nanofillers on rheological behavior of PMMA-based orthopedic materials.
abstract: In this investigation, calcium-deficient hydroxyapatite (CDHA) nanocrystals with needle-like geometry were synthesized and incorporated with Poly(methyl methacrylate), PMMA, to form CDHA-PMMA nanocomposites. Rheological behaviors of the PMMA-CDHA melting suspensions were systematically investigated in terms of solid loading and aspect ratio of the CDHA nanoparticles. The maximum solid loadings of nano-CDHA particles with aspect ratios of 7.2, 10.4, and 17 were determined to be 28, 31, and 57%, respectively. An increase in solid concentrations causes pronounced shear-thinning behavior. This result suggests that a strong interaction, including Van der Waals attraction and mechanical interlocking, between the nano-CDHA particles makes the nanocomposite mixture more non-Newtonian. Furthermore, it was found that packing efficiency and yield strength in the suspension were strongly influenced by the aspect ratio, especially above the critical value of 8.8. The obtained critical aspect ratio and solid content provide not only appropriate design in the PMMA-CDHA polymeric suspension for fabrication process but also optimal conditions for the fabrication of orthopedic devices via injection molding or extrusion.
authors.affiliation: Department of Materials Science and Engineering, National Chiao-Tung University, 1001 Ta-hsueh Rd., Hsinchu, Taiwan, Republic of China.
authors.forename: Tse-Ying
authors.initials: TY
authors.lastname: Liu
authors.forename: San-Yuan
authors.initials: SY
authors.lastname: Chen
authors.forename: Dean-Mo
authors.initials: DM
authors.lastname: Liu
mesh_terms: D001672:Biocompatible Materials; D003188:Composite Resins; D017886:Durapatite; D008422:Materials Testing; D009983:Orthopedic Equipment; D019904:Polymethyl Methacrylate; D012212:Rheology; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D003188:Composite Resins; D019904:Polymethyl Methacrylate; D017886:Durapatite