Thermo-Mechanical Behavior of Poly(ether ether ketone): Experiments and Modeling.
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ABSTRACT:
SUBMITTER: Drozdov AD
PROVIDER: S-EPMC8199459 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Herein, the interface of epoxy and graphene oxide (GO) is tailored through hydroxylated poly(ether ether ketone) (HPEEK). The resultant modification (HPEEK-g-GO) improved the interfacial adhesion between epoxy and carbon fiber (CF) in the laminates. This strategy resulted in improved tensile strength, modulus, and storage modulus by 8, 10, and 26%, respectively, with respect to control samples (epoxy/CF laminates). The HPEEK-g-GO was thoroughly characterized using spectroscopic techniques and was infused using vacuum-enhanced resin infusion technology into the epoxy/CF laminates. To address the challenges involved with primary agglomeration, the composite formulation was subjected to mechanical stirring coupled with bath sonication throughout the mixing process. The improved structural properties in epoxy/CF laminates were attributed to HPEEK-g-GO "interconnects", which provided the necessary reinforcement owing to better interfacial adhesion with the CF mat as inferred from the fracture surface morphology assessed using SEM. In addition, the epoxy laminates containing HPEEK-g-GO also showed flame-retardant properties along with good thermal stability. The electromagnetic interference shielding capability of the modified laminates was also evaluated in the frequency range of 12-18 GHz. It was observed that the laminates exhibited a shielding effectiveness of -50 dB. Thus, this strategy offers some promise in fabricating epoxy/CF laminates with multifunctional properties through HPEEK-g-GO "interconnects".
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Project description:Spinal fusion devices can be fabricated from composites based on combining hydroxyapatite and poly(ether ether ketone) phases. These implants serve as load-bearing scaffolds for the formation of new bone tissue between adjacent vertebrae. In this work, we report a novel approach to covalently bond hydroxyapatite and poly(ether ether ketone) to produce a novel composite formulation with enhanced interfacial adhesion between phases. Compared to non-linked composites (HA_PEEK), covalently linked composites (HA_L_PEEK), loaded with 1.25 vol% hydroxyapatite, possessed a greater mean flexural strength (170 ± 5.4 vs 171.7 ± 14.8 MPa (mean ± SD)) and modulus (4.8 ± 0.2 vs 5.0 ± 0.3 GPa (mean ± SD)). Although the mechanical properties were not found to be significantly different (p > 0.05), PEEK_L_HA contained substantially larger hydroxyapatite inclusions (100-1000 µm) compared to HA_PEEK (50-200 µm), due to the inherently agglomerative nature of the covalently bonded hydroxyapatite and poly(ether ether ketone) additive. Larger inclusions would expectedly weaken the HA_L_PEEK composite; however, there is no significant difference between the flexural modulus of poly(ether ether ketone) with respect to HA_L_PEEK (p = 0.13). In addition, the flexural modulus of HA_PEEK is significantly lower compared to poly(ether ether ketone) (p = 0.03). Ultimately, covalent linking reduces hydroxyapatite particulate de-bonding from the polymeric matrix and inhibits micro-crack development, culminating in enhanced transfer of stiffness between hydroxyapatite and poly(ether ether ketone) under loading.
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Project description:A strategy for the preparation of bioactive poly-ether-ether-ketone/hydroxyapatite (PEEK/HA) composites was proposed in this study with the aim of controlling the biological and mechanical properties of different parts of the composites. The strategy integrated solvent-based extrusion freeforming 3D printing technology in order to print high-resolution HA scaffolds and compression molding processes for the production of bioactive PEEK/HA composites. To this end, an optimized model, established using response surface methodology, was employed to optimize the extrusion process parameters on the basis of accurate characterization of the extrusion pressure, and the effects of the filament/pore sizes on the PEEK infiltration depth into the HA scaffold were investigated. The results of scanning electron microscopy and computed tomography analyses revealed that the PEEK/HA composites exhibited a uniform microstructure and a good interface between the HA filaments and the PEEK matrix following the optimization of the process parameters. The HA scaffolds were fully infiltrated by PEEK in both vertical and lateral directions with an infiltration depth of 3 mm while maintaining the HA network structure and uniformity. The biological and mechanical performance test results validated that the PEEK/HA composites possessed excellent biocompatibility as well as yields and compressive strengths within the range of human cortical bone suitable for load-bearing applications.
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Project description:Rapid cooling in fast-rate manufacturing processes such as additive manufacturing and stamp forming limits the development of crystallinity in semicrystalline polymer nanocomposites and, therefore, potential improvements in the mechanical performance. While the nucleation, chain mobility, and crystallization time from rapid cooling are known competing mechanisms in crystallization, herein we elucidate that the crystalline morphology and architecture also play a key role in tuning the mechanical performance. We explore how modifying the spherulite morphology via a cellulose nanocrystal (CNC) and graphene nanoplatelet (GNP) hybrid system in their pristine form can improve or preserve the mechanical properties of poly(ether ether ketone) (PEEK) nanocomposites under two extreme cooling rates (fast -460 °C/min and slow -0.7 °C/min). A scalable manufacturing methodology using water as the medium to disperse the powder system was developed, employing a CNC as a dispersing agent and stabilizer for PEEK and GNP. Despite the expected limited mechanical reinforcement due to thermal degradation, CNCs significantly impacted PEEK's crystalline architecture and mechanical performance, suggesting that surface interactions via lattice matching with PEEK's (200) crystallographic plane play a critical role in engineering the microstructure. In fast cooling, the CNC and CNC:GNP systems reduced the crystallinity, respectively, yet led to minimizing the reduction in the tensile strength and maintaining the tensile modulus at the Neat level in slow cooling. With slow cooling, crystallinity remained relatively unchanged; however, the addition of CNC:GNP improved the strength and modulus by ∼10% and ∼16%, respectively. These findings demonstrate that a hybrid nanomaterial system can tailor PEEK's crystalline microstructure, thus presenting a promising approach for enhancing the mechanical properties of PEEK nanocomposites in fast-rate processes.
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