Polyetheretherketone Polymer Research Articles

Characterization of friction stir-based linear continuous joining of aluminium alloy to structural polymer

Dissimilar continuous joining of lightweight metal alloys to structural polymer is a major manufacturing challenge, demanding feasible and reliable solutions. Through-slot extrusion joining (TSEJ) is a friction stir-based processing technique investigated in the manufacturing of continuous linear joints between aluminium alloy AA5754 overlapping structural polymer polyether ether ketone (PEEK). An intermediate rigid and thin titanium extrusion die protects the polymer locally from thermal degradation and promotes the formation of a continuous double hook-like feature of extruded aluminium into the polymer component along the joint path. The structure of the joint provides macro-mechanical interlocking between the joined components. A set of four tools, and other key process parameters, were investigated for process stability, tensile-shear strength, and microstructure. The best TSEJ condition is chosen for microstructural analysis via optical microscopy and scanning electron microscopy. Three distinct failure modes were identified. The best condition provided an average tensile-shear load of 110 kN/m. The tool position with bias toward the flow side of the extrusion slot shows to improve the strength of joints. The microstructural analysis along the interface of AA5754 to PEEK exhibits micro-mechanical interlocking, intercalated layers of these materials and adhesion as joining mechanisms.

Evaluation of Cytocompatibility of PEEK-Based Composites as a Function of Manufacturing Processes.

The biocompatible polymer polyetheretherketone (PEEK) is a suitable candidate to be part of potential all-polymer total joint replacements, provided its use is associated with better osseointegration, mechanical performance, and wear resistance. Seeking to meet the aforementioned requirements, respectively, we have manufactured a PEEK composite with different fillers: carbon fibers (CF), hydroxyapatite particles (HA) and graphene platelets (GNP). The mechanical outcomes of the composites with combinations of 0, 1.5, 3.0 wt% GNP, 5 and 15 wt% HA and 30% of wt% CF concentrations pointed out that one of the best filler combinations to achieve the previous objectives was 30 wt% CF, 8 wt% HA and 2 wt% of GNP. The study compares the bioactivity of human osteoblasts on this composite prepared by injection molding with that on the material manufactured by the Fused Filament Fabrication 3D additive technique. The results indicate that the surface adhesion and proliferation of human osteoblasts over time are better with the composite obtained by injection molding than that obtained by 3D printing. This result is more closely correlated with morphological parameters of the composite surface than its wettability behavior.

A Composite of Polyether Ether Ketone and Silica‐Coated Copper Particles for Creating Tailored Conductive Tracks via Laser Printing

AbstractConventional substrates for optoelectronic systems include inorganic or organic carrier materials; however, these systems are typically subjected to environmentally harmful multistep processes to prepare printed circuit boards. To mitigate these issues, the present article reports a polyether ether ketone (PEEK)‐based composite densely filled with copper microparticles, prepared using a simple, cost‐effective, and sustainable synthesis method. The material exhibits high thermal conductivity but is electrically nonconductive prior to undergoing laser treatment. To prevent the composite from exhibiting electrical conductivity, the copper particles are coated with a thin silica layer through a sol–gel reaction. The thermal stability of PEEK and the Cu–PEEK composites with Cu contents of up to 70 vol%, which are prepared via heat melding, is investigated by thermogravimetric analysis, differential scanning calorimetry, and Fourier‐transform infrared spectroscopy to clarify the manner in which copper affects the chemical structure of the polymer. The developed composite exhibits a significantly higher thermal conductivity than that of the unfilled PEEK polymer. This paper also describes the effects of laser treatment on the surface morphology. Overall, this study suggests that conductive tracks with low electrical resistance can be created on electrically insulating substrates with high thermal conductivity.

Rotary Friction Welding of Polyetheretherketone Biopolymer Rods Using Variable Rotational Speed.

Polyetheretherketone (PEEK) is a promising biomaterial due to its excellent mechanical properties. Most PPEK manufacturing methods include additive manufacturing, injection molding, grinding, pulse laser drilling, or incremental sheet forming. Rotary friction welding (RFW) is a promising bonding technique in many industries. However, very few studies have focused on the RFW of PEEK. Conventionally, the number of revolutions is fixed during the welding process. Remarkably, the rotary friction welding of PEEK polymer rods using an innovative variable rotational speed is investigated in this study. The average bending strength of the welded part using a three-stage transformation rotational speed was enhanced by about 140% compared with a rotational speed of 1000 rpm. The advantage of computer numerical controlled RFW of PEEK using variable rotational speed is a reduced cycle time of RFW. A reduction in cycle time of about 6% can be obtained using the proposed RFW with a three-stage transformation rotational speed. The innovative approach provides low environmental pollution and high energy efficiency and complies with sustainable development goals.

Sulfonated Polyether Ketone Membranes Embedded with Nalidixic Acid-An Emerging Controlled Drug Releaser.

The effective administration of medication has advanced over decades, but the medical community still faces significant demand. Burst release and inadequate assimilation are major drawbacks that affect wound healing efficiency, leading to therapy failure. The widespread application of polymers in biomedical research is significant. The polyether ether ketone (PEEK) family is known for its biocompatibility, inertness, and semi-crystalline thermoplastic properties. In our present studies, we have chosen a member of this family, polyether ketone (PEK), to explore its role as a drug carrier. The PEK backbone was subjected to sulfonation to increase its hydrophilicity. The response surface methodology (RSM) was used to optimize the sulfonation process based on the time, degree of sulfonation, and temperature. The PEK polymer was sulfonated using sulfuric acid at 150 °C for 6 h; back titration was performed to quantify the degree of sulfonation, with 69% representing the maximum sulfonation. SPEK and nalidixic sodium salt were dissolved in dichloroacetic acid to create a thin membrane. The physiological and morphological properties were assessed for the SPEK membrane. The studies on drug release in distilled water and a simulated body fluid over the course of 24 h revealed a controlled, gradual increase in the release rate, correlating with a mathematical model and demonstrating the zero-order nature of the drug release. Hemolysis on the SPEK membrane revealed lower toxicity. The SPEK membrane's biocompatibility was established using in vitro cytotoxicity tests on the Vero (IC50: 137.85 g/mL) cell lines. These results confirm that the SPEK membranes are suitable for sustained drug release.

Machinability of 3D printed peek reinforced with short carbon fiber

The new manufacturing technologies are advancing and developing rapidly, gradually causing some conventional processes used until now to become obsolete or relegated to second place. One of the challenges of emerging manufacturing processes is sustainability, decreasing raw materials and recycling used components. Additive manufacturing is among these new technologies, allowing the fabrication of complex geometries and the reduction of waste by producing parts close to their commissioning (i.e., net-shape or near-net-shape manufacturing) and the recycling of used components to develop raw material.One of the most widely used thermoplastic materials in manufacturing is polyether ether ketone (PEEK), mainly due to its good mechanical properties. The use of fibers as a means of reinforcement in polymeric materials has witnessed a significant surge in recent times to enhance mechanical properties. Recycling these fibers from other components after service life, giving a second life to these materials, would have a high impact in terms of sustainability. CFRPs have been widely used in different sectors in the last decades, providing a source of carbon fibers suitable for use as polymer reinforcement in additive manufacturing.Processing operations are often necessary to reach dimensional and joining (e.g., assembly) specifications. Despite its widespread use in the industry requiring certain postprocessing operations, just a few publications analyze the machinability of PEEK polymer. The addition of carbon fiber reinforcement influences the machinability of the polymer. This study uses orthogonal cutting tests to focus on the machinability of 3D printed PEEK with and without short carbon fiber reinforcement through orthogonal cutting tests.The additive process procedure is analyzed in terms of printing orientations. The effect of machining parameters (cutting speed and the depth of cut) on the force generation, the superficial damage, and the temperature reached in the samples are also analyzed and related with the addition of reinforcement.

Effects of the Applied Potential on the Performance of Polysulfone Membranes Functionalized with Sulfonated Polyether Ether Ketone Polymers.

The global water crisis growth has led to a tremendous increase in membrane technology research. Membranes are favored over many other technologies for water treatment because, in principle, they require no chemical additives and can be used isothermally at low temperatures. Membranes that can reject contaminants and salts, produce adequate permeate flux values, and require minimal cleaning are highly demanded. However, most synthesized membranes on the market have associated problems, such as membrane fouling; inverse relationships between flux and solute rejection; and the high cost of synthesis, operation, and maintenance. Therefore, there is a continuied need to produce membranes with properties that make them able to sustain flux and selectivity over time. This research study focused on increasing the surface charge and hydrophilicity of polysulfone (PSf) membranes by incorporating sulfonate-functionalized poly-ether-ether-ketone (SPEEK) into PSf/N-Methyl-2-pyrrolidone (PSf/NMP) membranes. The sulfonation of the PEEK provided a net increase in negative charge on the surface of the membranes that enabled charge repulsion to take place, thus increasing the rejection of ions. In this project, the effect of the applied potential on the performance of SPEEK: PSf/NMP membranes was evaluated. The characterization of the as-synthesized membranes was carried out using the surface's structure and morphology, contact angle, and zeta potential. Furthermore, a voltage of 1.5 V was applied to the membranes in the presence of various salts (sodium chloride, calcium chloride, and potassium chloride salts) to evaluate the effects of the applied potential on solute rejection. It was found that both the permeability and the selectivity of the membranes increased when the voltage was applied. The obtained results indicate that incorporating SPEEK into PSf/NMP membranes increased the hydrophilicity of the membranes, and under the applied voltage, the incorporation allowed it to function as an electrodialysis process that is capable of removing ions from water bodies by utilizing the charge repulsion of ions.

A Comprehensive Review on Manufacturing and Characterization of Polyetheretherketone Polymers for Dental Implant Applications.

Aging, tooth trauma, and pathological infections cause partial or total tooth loss, leading to the usage of dental implants for restoration treatments. As such, mechanical and tribological properties play an important role in the osseointegration and durability of these implants. Metallic and ceramic implants are shown to have mechanical properties much higher than the natural teeth structure, leading to stress shielding-related failure of an implant. Stress shielding occurs due to the difference in the elastic modulus between the implant material and the surrounding teeth structure, leading to bone loss and implant failure. The implant's properties (i.e., mechanical) should be as close as human teeth components. To achieve this, various materials and coatings are being developed and investigated. This review is a comprehensive survey of materials, manufacturing, coating techniques, and mechanical and tribological characterizations of dental implants, with a particular focus on polyetheretherketone (PEEK) as a potential alternative dental implant material. PEEK has mechanical properties similar to natural teeth, which make it a promising material for dental implants. The findings of this review suggest that PEEK offers superior biocompatibility, osseointegration, and wear resistance for implant applications. With the help of bioactive coatings, bone growth on the implant surface can be promoted. In addition, PEEK dental implants made using three-dimensional (3D) printing technology can significantly reduce the cost of implants, making them more affordable and increasing access to dental care, which can improve oral health significantly. In summary, this review highlights the potential of PEEK as a promising alternative dental implant material, and provides an overview of various techniques, testing, and future directions for PEEK dental implants.

Comparing the shear bond strength of veneering materials to the PAEKs after surface treatments

BackgroundThis study aimed to evaluate the impact of various surface treatments on the shear bond strength (SBS) of polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) polymers to indirect laboratory composite (ILC) and lithium disilicate ceramic (LDC) veneering materials.MethodsPolymer specimens (7 × 7x2 mm) were sectioned from PEEK and PEKK discs (N = 294) and randomly allocated to 7 groups (n = 20); untreated (Cnt), plasma (Pls), 98% sulfuric acid (Sa), sandblasting with 110 µm Al2O3 (Sb), tribochemical silica coating with 110 µm silica modified Al2O3 (Tbc), Sb + Sa, Tbc + Sa. Scanning electron microscopy assessments were performed on one sample of each treatment group, and veneering materials were applied to the remaining specimens (n = 10). The specimens were subjected to the SBS test after being soaked in distilled water (24 h, 37 °C). Three-way ANOVA, independent sample t-test, and Tukey HSD test were performed for statistical analyses (α = .05).ResultsThe surface treatment, polymer, veneering material types, and their interactions were significant on SBS results according to the 3-way ANOVA (p < 0.001). The SBS values of ILC veneered groups were significantly higher than LDC groups, regardless of surface treatment and polymer type (p < 0.05). The highest SBS values were obtained for Sa-applied ILC veneered PEEK (21.55 ± 1.45 MPa) and PEKK (17.04 ± 1.99 MPa) polymer groups (p < 0.05).ConclusionThe effect of surface treatment and veneering materials may be significant on the SBS values of PAEKs. Therefore, the application parameters of surface treatments should be more specified for the applied veneering material and polymer type.

Effects on the Thermo-Mechanical and Interfacial Performance of Newly Developed PI-Sized Carbon Fiber-Polyether Ether Ketone Composites: Experiments and Molecular Dynamics Simulations.

In this study, polyether ether ketone (PEEK) composites reinforced with newly developed water-dispersible polyimide (PI)-sized carbon fibers (CFs) were developed to enhance the effects of the interfacial interaction between PI-sized CFs and a PEEK polymer on their thermo-mechanical properties. The PI sizing layers on these CFs may be induced to interact vigorously with the p-phenylene groups of PEEK polymer chains because of increased electron affinity. Therefore, these PI-sized CFs are effective for improving the interfacial adhesion of PEEK composites. PEEK composites were reinforced with C-CFs, de-CFs, and PI-sized CFs. The PI-sized CFs were prepared by spin-coating a water-dispersible PAS suspension onto the de-CFs, followed by heat treatment for imidization. The composites were cured using a compression molding machine at a constant temperature and pressure. Atomic force and scanning electron microscopy observations of the structures and morphologies of the carbon fiber surfaces verified the improvement of their thermo-mechanical properties. Molecular dynamics simulations were used to investigate the effects of PI sizing agents on the stronger interfacial interaction energy between the PI-sized CFs and the PEEK polymer. These results suggest that optimal amounts of PI sizing agents increased the interfacial properties between the CFs and the PEEK polymer.

Polyetheretherketone blends with excellent properties achieved via crosslinkable polyetherimide at high temperatures

AbstractWith the development of science and technology, polymer materials that work at high temperatures are widely needed. However, currently available polymers are limited to relatively low operating temperatures, with various properties rapidly degrading at high temperatures. Here, with crosslinked polyetherimide (c‐PEI), polyetheretherketone (PEEK) is modified by mechanical blending and extrusion granulation to prepare c‐PEI/PEEK polymer blends. Compared with the commercial polyetherimide (s‐PEI) without crosslinking groups, the construction of its crosslinking network in c‐PEI further restricts the movement of molecular segments and more significantly improves the thermodynamic properties of PEEK at high temperature. This work systematically investigates the effect of the crosslinking degree of polymer blends on performance and balances processability and other properties by controlling the crosslinking degree. Furthermore, this work demonstrates a feasible strategy to fabricate high‐performance polymer materials with high temperature resistance.

Surface grafting of Poly (ether ether ketone) on silica particles as novel filler for dental composites: Physico-chemical characterization

This study aimed to describe the fabrication of a novel dental composite by surface modification of silica fillers with polyether ether ketone (PEEK) and assess surface coverage of fillers and the effect of different concentration of modified fillers on degree of conversion, flexural strength, polymerization shrinkage, water sorption and solubility, viscosity and thermal expansion of the formulated composites. In this experimental study, aminosilane derivative of PEEK was synthesized and grafted to the silica filler surface, then evaluated using a fourier transform infrared spectroscopy (FTIR), and thermo-gravimetric analysis (TGA). Silica-PEEK fillers were then mixed with Bis-GMA/TEGDMA resin base in 10, 30, and 50 wt%. The most relevant physico-chemical properties were evaluated and compared with a control composite resin group containing conventional 3-(methacryloxypropyl) trimethoxysilane (γ-MPS) modified fillers. Data were analyzed by ANOVA and Tukey’s HSD test. (α = 5%). The experimental composite with 30% modified fillers showed highest flexural strength and degree of conversion (DC) ( p &lt; 0.05), and comparable polymerization shrinkage and viscosity to the control composites ( p &gt; 0.05). After thermocycling, the composite with 30% modified fillers showed the lowest solubility and water sorption ( p &lt; 0.05). Surface modification of silica fillers with PEEK polymer significantly increases the resistance of the filler–matrix interface to hydrolysis. The above mentioned intervention can improve mechanical properties of the composite and may be considered as a promising protocol to reduce the failure of dental composites.

Characteristics of Hybrid Bioglass-Chitosan Coatings on the Plasma Activated PEEK Polymer

Polyetheretherketone (PEEK) is a biocompatible, chemically and physically stable radiolucent polymer that exhibits a similar elastic modulus to the normal human bone, making it an attractive orthopedic implant material. However, PEEK is biologically inert, preventing strong enough bonding with the surrounding bone tissue when implanted in vivo. Surface modification and composite preparation are the two main strategies for the improvement of the bioactivity of PEEK. In this study, the plasma activated PEEK surfaces with the embedded bioglass, chitosan, and bioglass-chitosan mixed layers applying from the solution dip-coating technique were investigated. The most prominent factors affecting the coating biocompatibility are strictly connected with the composition of its outer surface (its charge and functional groups), hydrophilic-hydrophobic character, wettability and surface free energy, and topography (size of pores/substructures, roughness, stiffness), as well as the personal characteristics of the patient. The obtained surfaces were examined in terms of wettability and surface-free energy changes. Additionally, FTIR (Fourier Transformation Infrared Spectrometry) and SIMS (Secondary Ion Mass Spectrometry) were applied to establish and control the coating composition. Simultaneously the structure of coatings was visualized with the aid of SEM (Scanning Electron Microscopy). Finally, the obtained systems were incubated in SBF (Simulated Body Fluid) to verify the modifications' influence on the bioactivity/biocompatibility of the PEEK surface. Different structures with variable compositions, as well as changes of the wettability, were observed depending on the applied modification. In addition, the incubation in SBF suggested that the bioglass-chitosan ratio influenced the formation of apatite-like structures on the modified PEEK surfaces.

Comparative analysis of stress and deformation distribution in implant supported telescopic systems made of different materials

Background/Aim. In implant prosthetics, there is an increasing use of materials that, with their mechanical characteristics, can alleviate the negative consequences of implant stress. The aim of this study was to conduct a comparative analysis of stress distribution and deformation of implant-supported telescopic systems and surrounding structures made of different materials using the finite element method. Methods. The 3D finite element models were prepared using the SolidWorks program (SolidWorks 2018, Concord, MA, USA). Two models of telescopic crowns with the characteristics of polyetherether-ketone (PEEK) polymer and cobalt-chromium (Co-Cr) alloy faceted with feldspar ceramics were used. The models were loaded with an axial force of 150 N in the region of the central fossa. The analysis of stress and strain distribution was per-formed by the finite element method in the Ansys software (ANSYS Workbench 16; Ansys Inc., Pittsburg, PA, USA). Results. Implant-supported telescopic crowns made of PEEK polymer significantly reduced stress in the implant and abutment neck area compared to the conventional Co-Cr crown veneered ceramic. At the level of bone structure, both models showed a concentration of stress at the level of the cortical bone, while the trabecular bone was significantly less exposed to stress. Under the same conditions, the degree of deformation of the secondary telescopic crown was more pronounced in models with PEEK polymer characteristics. Conclusion. Owing to their mechanical characteristics, PEEK polymers can be the materials of choice in the fabrication of superstructures on implants. Given that this in vitro study was accompanied by limitations, further research is needed to confirm the superior role of PEEK material in implant prosthetics.

Ultrasonic Welding of Additively Manufactured PEEK and Carbon-Fiber-Reinforced PEEK with Integrated Energy Directors

The thermoplastic polymer polyether ether ketone (PEEK) offers thermal and mechanical properties comparable to thermosetting polymers, while also being thermally re-processable and recyclable as well as compatible with fused filament fabrication (FFF). In this study, the feasibility of joining additively manufactured PEEK in pure and short carbon-fiber-reinforced form (CF-PEEK) is investigated. Coupon-level samples for both materials were fabricated using FFF with tailored integrated welding surfaces in the form of two different energy director (ED) shapes and joined through ultrasonic polymer welding. Using an energy-driven joining process, the two materials were systematically investigated with different welding parameters, such as welding force, oscillation amplitude and welding power, against the resulting weld quality. The strengths of the welded bonds were characterized using lap-shear tests and benchmarked against the monotonic properties of single 3D-printed samples, yielding ultimate lap-shear forces of 2.17kN and 1.97kN and tensile strengths of 3.24MPa and 3.79MPa for PEEK and CF-PEEK, respectively. The weld surfaces were microscopically imaged to characterize the failure behaviors of joints welded using different welding parameters. Samples welded with optimized welding parameters exhibited failures outside the welded region, indicating a higher weld-strength compared to that of the bulk. This study lays the foundation for using ultrasonic welding as a glue-free method to join 3D-printed high-performance thermoplastics to manufacture large load-bearing, as well as non-load-bearing, structures, while minimizing the time and cost limitations of FFF as a fabrication process.

Surface Modifications of High-Performance Polymer Polyetheretherketone (PEEK) to Improve Its Biological Performance in Dentistry.

This comprehensive review focuses on polyetheretherketone (PEEK), a synthetic thermoplastic polymer, for applications in dentistry. As a high-performance polymer, PEEK is intrinsically robust yet biocompatible, making it an ideal substitute for titanium-the current gold standard in dentistry. PEEK, however, is also inert due to its low surface energy and brings challenges when employed in dentistry. Inert PEEK often falls short of achieving a few critical requirements of clinical dental materials, such as adhesiveness, osseoconductivity, antibacterial properties, and resistance to tribocorrosion. This study aims to review these properties and explore the various surface modification strategies that enhance the performance of PEEK. Literatures searches were conducted on Google Scholar, Research Gate, and PubMed databases using PEEK, polyetheretherketone, osseointegration of PEEK, PEEK in dentistry, tribology of PEEK, surface modifications, dental applications, bonding strength, surface topography, adhesive in dentistry, and dental implant as keywords. Literature on the topics of surface modification to increase adhesiveness, tribology, and osseointegration of PEEK were included in the review. The unavailability of full texts was considered when excluding literature. Surface modifications via chemical strategies (such as sulfonation, plasma treatment, UV treatment, surface coating, surface polymerization, etc.) and/or physical approaches (such as sandblasting, laser treatment, accelerated neutral atom beam, layer-by-layer assembly, particle leaching, etc.) discussed in the literature are summarized and compared. Further, approaches such as the incorporation of bioactive materials, e.g., osteogenic agents, antibacterial agents, etc., to enhance the abovementioned desired properties are explored. This review presents surface modification as a critical and essential approach to enhance the biological performance of PEEK in dentistry by retaining its mechanical robustness.

Effect of 3D printing process parameters on surface and mechanical properties of FFF-printed PEEK

Fused filament fabrication (FFF), as one of the most commonly used additive manufacturing (AM) technology, draws lots of attention in fabrication of polymer-based materials because of its simplicity and relatively low-cost. Recent advances in FFF printing enables fabrication of high-temperature and high-performance polymeric materials such as polyether ether ketone (PEEK). The objective of this work is to evaluate the effects of different process parameters of FFF printing on mechanical and tribological properties of PEEK polymers. The properties of interest include surface mechanical properties measured through indentation and roughness tests as well as bulk mechanical properties defined by tensile tests. We used the Taguchi method along with the analysis of variances (ANOVA) to determine the process parameters with the most significant effect on the outcomes. The process parameters of interest are nozzle temperature, platform temperature, infill percentage, layer height, and print speed. Nozzle temperature and layer height were the process parameters that significantly influenced the resultant roughness as well as the elastic modulus measured via indentation test (Nozzle temperature: p = 0.001, contribution = 36.1 % &p = 0.008, contribution = 41.9 %; layer height: p < 0.001, contribution = 41 % &p = 0.026, contribution = 29.7 % for roughness & elastic modulus measured by micro-indentation, respectively). There were no process parameters significantly affecting hardness and creep. For the bulk mechanical properties measured by tensile test, such as elastic modulus, yield strength, ultimate strength and modulus of resilience, infill percentage (p < 0.001 for all the measured properties), platform temperature (elastic modulus: p < 0.001, contribution = 8.9 %; ultimate strength: p = 0.024, contribution = 5.5 %), nozzle temperature (elastic modulus: p = 0.013, contribution = 3.5 %; ultimate strength: p = 0.041, contribution = 3.9 %; modulus of resilience: p = 0.034, contribution = 18.2 %) and layer height (elastic modulus: p = 0.005, contribution = 5.9 %; ultimate strength: p = 0.026, contribution = 4 %) were among the factors that show the most significant effect. Our results suggested that through an accurate control of FFF process parameters, this simple yet affordable three-dimensional (3D) printing technology can be utilized to fabricate PEEK polymers with desired mechanical and tribological performance.

Evaluation of Microscopic Damage of PEEK Polymers under Cyclic Loadings Using Molecular Dynamics Simulations.

Full-atomic molecular dynamics simulations were conducted to investigate the time evolution of microscopic damage in polyetheretherketone (PEEK) polymers under cyclic loading conditions. Three characteristics were used to quantify microscopic damage: entropy, distribution of the end-to-end distance of polymers, and the volume fraction of voids. Our results show that the degree of disentanglement of polymers and the volume fraction of voids increase with cyclic loading, which may lead to entropy generation. Uniaxial tensile strength simulations of the polymer system before and after cyclic loading were performed. The tensile strength after cyclic loading was lower than that before loading. Furthermore, two systems with the same entropy and different loading histories showed almost the same strength. These results imply that entropy generation is expressed as the total microscopic damage and can potentially be employed for effective evaluation of the degradation of material characteristics.

Evaluation of 3D printed PEEK and other 3D printed biocompatible materials as healthcare devices

Introduction and Aim: Additive manufacturing has sought a widespread attention and higher rate of development which can also be modeled by processing of the data acquired by medical Computer Tomography scan. The object is built on a built plate of the printer in layers to form a final required model. Thus, a patient-specific model can be created from imaging data set. Materials available for such printing are elastomers, polymers, metals, or ceramics. The polymer, Polyether ether ketone (PEEK) has been used in health care applications, such as medical devices, and implants due to its high strength, biocompatibility, and light weight. Stainless steel (316L) is commonly used due to its strength, bio-tolerance, corrosion resistance and its formability. The aim of this study was to compare the mechanical strength and biocompatibility of medical grade PEEK and stainless steel. Material and Methods: The test sample of PEEK was prepared using unreinforced PEEK (450G-Victrex Plc., Lancashire, UK) at the Prototyping Lab with a 3D-Printer - INTAMSYS - FUNMAT HT. Samples of stainless steel was printed using the iFusion SF1 Metal 3D Printer using Powder Bed Fusion (PBF) technology. The mechanical tests such as compressive, impact, and tensile tests were performed using an electromechanical universal testing machine (UTM) model- Zwick/Roell Z020 with a 20kN load cell. Biocompatibility tests were done using L929 cells to assess the cytotoxicity of the dental materials. Results: The tensile strength of PEEK polymer was 70+1.6 and the impact strength of PEEK polymer was 289 J/m. Conclusion: The tensile strength of stainless steel was higher compared to that of PEEK polymer, and the impact strength of PEEK polymer higher compared to stainless steel. Thus, it can be concluded that both biomaterial such as 316L stainless steel and PEEK are non-toxic to fibroblast.

In Situ Contact Analysis of Polyetheretherketone under Elastohydrodynamic Lubrication.

The influence of the complex material behavior of thermoplastic polymers in lubricated contacts is poorly understood. It affects the optimal design of power-transmitting thermoplastic machine elements and the exploitation of its potential, e.g., lightweight design, low-noise operation, and cost-effective manufacturing when injection-molded. This study applies the in situ thin-film sensor technology on a twin-disk tribometer in order to study the elastohydrodynamic lubrication of rolling–sliding contacts with the thermoplastic polymer polyetheretherketone. The results provide insights into the effects and relevance of its thermoplastic material properties. Pressure measurements reveal a typical hydrodynamic profile in combination with a large deformation of the contact zone. The influence of speed and slip ratio is thereby negligible. The temperature rise is low compared to elastohydrodynamically lubricated contacts with steel and is mainly influenced by the slip ratio as well as the load, whereas speed plays a subordinated role. In general, the heat generation is governed by shearing and backflow in the contact inlet zone at low slip ratios and shearing in the contact zone at high slip ratios. No effects attributed to viscoelasticity or loading frequency were observed at the operating conditions considered.