Abstract
This study is focused on carbon nanostructures (CNS), including both carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), reinforcement of medical‐grade polyetheretherketone (PEEK), and in vitro bioactivity for biomedical structural applications. CNS/PEEK scaffolds and bulk specimens, realized via fused filament fabrication (FFF) additive manufacturing, are assessed primarily in the low‐strain linear‐elastic regime. 3D printed PEEK nanocomposites are found to have enhanced mechanical properties in all cases while maintaining the desired degree of crystallinity in the range of 30–33%. A synergetic effect of the CNS and sulfonation toward bioactivity is observed—apatite growth in simulated body fluid increases by 57% and 77%, for CNT and GNP reinforcement, respectively, doubling the effect of sulfonation and exhibiting a fully‐grown mushroom‐like apatite morphology. Further, CNT‐ and GNP‐reinforced sulfonated PEEK recovers much of the mechanical losses in modulus and strength due to sulfonation, in one case (GNP reinforcement) increasing the yield and ultimate strengths beyond the (non‐sulfonated) printed PEEK. Additive manufacturing of PEEK with CNS reinforcement demonstrated here opens up many design opportunities for structural and biomedical applications, including personalized bioactivated surfaces for bone scaffolds, with further potential arising from the electrically conductive nanoengineered PEEK material toward smart and multifunctional structures.
Highlights
Polyetheretherketone (PEEK) is a semicrystalline high-temperature structural polymer, originally developed by Imperial Chemical Industries, UK, in 1977.[1]
We discuss the physical characteristics of the nanoengineered PEEK structures achieved via fused filament fabrication (FFF) and present the results of the bioactivity experiments, which reveal a synergy between the carbon nanostructures (CNS) reinforcement of the fibers and the sulfonation process used to increase bioactivity
We conclude that CNS reinforcement increases the degree of crystallinity, while sulfonation has no significant effect on crystallinity of the printed PEEK and PEEK nanocomposites
Summary
Polyetheretherketone (PEEK) is a semicrystalline high-temperature structural polymer, originally developed by Imperial Chemical Industries, UK, in 1977.[1]. In FFF AM, a polymer filament is fed through a preheated nozzle to enable a layer-by-layer deposition to build a 3D structure This involves motion of the print head in the X- and Y- axes, while lowering the print bed in the Z-axis.[7] After each layer of deposition, the print bed is lowered and another layer is deposited on top of the preceding layer in a pattern dictated by the desired computer-aided design (CAD) model.[8] FFF is the most widely used AM technique due to its ease of use, fast fabrication, cost effectiveness, and ability to produce complex geometries without involving postmachining.[11] A variety of polymers and their composites can be processed by FFF, such as acrylonitrile butadiene styrene,[12] polylactic acid,[13] polyamides,[14] polypropylene,[15] and polycarbonate.[16,17] AM of high-temperature structural (modulus in excess of 1 GPa) thermoplastics, such as PEEK, has received enormous attention because of their wide applicability in many areas, including aerospace, energy, and orthopedics.[18]. The bioactivity tests reveal a synergy between the CNS and the effectiveness of the chemical treatment (sulfonation) used to enhance bioactivity on the PEEK surface.[20]
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