Polyetheretherketone Polymer Research Articles

Tribological Characterization of Polyether Ether Ketone (PEEK) Polymers Produced by Additive Manufacturing for Hydrodynamic Bearing Application

The coating materials commonly used in hydrodynamic bearings are the so-called “Babbitt metals” or “white metals”, as defined by ASTM B23-00. Their low Young’s modulus and yield point have encouraged researchers to find new coatings to overcome these limitations. In this paper, the friction and wear of PEEK are studied in a dry sliding environment (without lubrication) using a ball-on-disk tribometer and compared to those of Babbitt metal. Furthermore, the bond strength tests between PEEK and metals/alloys are evaluated. PEEK polymer samples were obtained from cylindrical rods, manufactured by an innovative process for polymer bonding on bearing surfaces, using additive manufacturing technology. The morphologies of the degraded surfaces were examined using a high-resolution metallurgical optical microscope (OM) and a scanning electron microscope (SEM). The coefficients of friction (CoF) were obtained under the alternating ball-on-disk dry tribometer. The results of the experimental activity show that PEEK polymers have CoFs of about 0.22 and 0.16 under the 1 and 5 N applied load, respectively. The CoF and wear volume loss results are reported and compared to the reference Babbitt coating.

A novel approach of restoring endodontically treated tooth by using cad-cam milled peek post and core system: A case report

The choice of appropriate definitive restoration of endodontically treated teeth should be guided by the amount of remaining hard tissues as well as functional and aesthetic considerations. Post and-core materials with biomechanical properties similar to the dentin could also be advantageous in reducing the risk of root fractures. The high performance polymer Poly-ether-ether-ketone (PEEK) is an example of one such type of material. This case report describes the restoration of endodontically treated mandibular premolar with the use of CAD-CAM milled post and core system followed by restoration with full coverage porcelain fused to metal crown.

Performance of PEEK based telescopic crowns, a comparative study

ObjectiveTelescopic crowns are suitable components of partial dentures to efficiently anchor dental supra-structures to teeth or dental implants and achieve high chewing performance and wear comfort.Usually alloy- or metal-based structures are used for the primary and the secondary crowns. The advantage is the possibility to produce precise structures with a high perfection and sufficient friction force, but the disadvantage is the corrosion instability. The recent introduction of zirconia ceramics has enabled the fabrication of ceramic primary crowns, thus reducing corrodibility.The novel application of the high-performance polymer polyetheretherketone (PEEK) as another metal-free alternative material offers a new perspective for such applications.Therefore, the aim of this work was to assess the performance of telescopic crowns of PEEK by comparing telescopic crowns based on the combination of PEEK (prim. crown) + PEEK (sec. crown) with the pairings ZrO2 (prim. crown) + PEEK (sec. crown) and CoCr-alloy (prim. crown) + PEEK (sec. crown). MethodsAll specimens were CAD/CAM planned and manufactured based on a model of a tooth 26. One master dental technician performed the post-treatment. For each group of material pairing, n = 9 telescopic crown pairs were manufactured and tested. Herein not only the maximum retention force was measured but also the retention force vs. pull-off distance were analyzed. As there is no commonly accepted test protocol available, the influence of various pull off speeds were tested as well. All measurements were first made with three blocks of three crowns (3C), subsequently with three blocks of two crowns (2C) and finally with nine single crowns (1C). The long-term behavior was estimated by performing 10.000 cycles, which is related to a life-time of more than 10 years. ResultsThe maximum retention force in case of PEEK + PEEK was higher in comparison to the other tested material pairings. In the range between 1 and 10 mm/ min pull off speed there was no significant influence by the pull off speed. More influence on the friction force would be expected by changes of the number of the crowns acting simultaneously. The friction force was decreasing with decreasing number of crowns but not linearly in any tested case. The long-term test has shown that the friction force remained constant. SignificanceThe performance of PEEK + PEEK telescopes is comparable with the usually applied material pairings. Over long time no loss in retention force could be observed. The retention force - distance progression in the PEEK + PEEK pairing offers more security against a possible loss of retention during repair or relining. For further tests of the performance of telescopic crowns or to estimate of friction force limits, a setup with at least two, but preferably three, crowns tested in parallel is suggested.

Surface Finishing of FDM-Fabricated Amorphous Polyetheretherketone and Its Carbon-Fiber-Reinforced Composite by Dry Milling.

In recent years, many investigations have been devoted to fused deposition modeling (FDM) of high-performance polymer-polyetheretherketone (PEEK) and carbon-fiber-reinforced PEEK (CF/PEEK) for biomedical and aerospace applications. However, the staircase effect naturally brought about by FDM restricts further applications of 3D-printed PEEK and its composites in high-temperature molds, medical implants, and precision components, which require better or customized surface qualities. Hence, this work aimed to reduce the staircase effect and improve the surface quality of 3D-printed PEEK and CF/PEEK parts by dry milling of the fluctuant exterior surface. The co-dependency between 3D printing parameters (raster angle and layer thickness) and milling parameters (depth of cut, spindle speed, and feed rate per tooth) were investigated through experiments. The difference in removal mechanisms for PEEK and CF/PEEK was revealed. It was confirmed that the smearing effect enhanced the surface quality based on the morphology analysis and the simulation model. Both the raster angle of +45°/−45° and the small layer thickness could improve the surface quality of these 3D-printed polymers after dry milling. A large depth of cut and a large feed rate per tooth were likely to deteriorate the finished polymer surface. The spindle speed could influence the morphologies without significant changes in roughness values. Finally, a demonstration was performed to verify that dry milling of 3D-printed amorphous PEEK and CF/PEEK parts could lead to a high surface quality for critical requirements.

Influence of non-thermal plasma systems and two favorable surface treatments on the shear bond strength of PAEKs to composite resin

This study aimed to investigate the effect of non-thermal plasma systems with and without two favorable surface treatment techniques on the surface roughness (Ra) and shear bond strength (SBS) of polyaryletherketone (PAEK) polymers to veneering composite resin material. A total of 288 (n = 144 for each polymer) Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) samples (7 73mm) were divided into the surface treatment methods (n = 16): untreated (CNT); dielectric barrier discharge air plasma treatment (DBD); atmospheric pressure plasma treatment with a plasma brush (APB); 98% sulfuric acid etching (SA); SA_DBD; SA_APB; tribochemical silica coating (TBC); TBC_DBD; TBC_APB. The Ra (n = 5) and scanning electron microscope (SEM) analyses (n = 1) were performed. A bonding agent was applied to the remaining samples (n = 10) and veneered with a composite resin. After storing in distilled water for 24 h at 37 °C, the SBS test was applied with a universal test machine, and the failure modes were examined with an optical microscope. The SBS and Ra data were statistically analyzed with Kruskal Wallis, two-way analysis of variance (ANOVA), and compared with Mann-Whitney_U and Tamhane tests (α = 0.05). The highest SBS value was observed in Groups SA (22.67 ± 1.48 MPa) for PEEK, Group TBC (18.91 ± 1.09 MPa) for PEKK polymer groups. The highest Ra values were determined in Group TBC_DBD for both polymers. While the TBC may enhance the SBS values of both polymers, the SA application is more effective for PEEK polymer regarding the SBS value. In contrast to the effect of DBD, APB application is beneficial for improving the bonding capacity of PAEKs.

Long-term surface modification of PEEK polymer using plasma and PEG silane treatment

Despite the several advantages of the Polyetheretherketone (PEEK) polymer, its wide application is limited due to its hydrophobic nature and poor surface adhesion performance. The plasma treatment can effectively transform the hydrophobic surface to hydrophilic. However, their effects are for a short duration, and the modified surfaces gradually lose their wetting and surface adhesion properties. In this work, we have reported a combined effect of plasma and PEG Silane treatment for permanent hydrophilic modification and improved adhesion strength of PEEK surfaces. The time-dependent changes in the contact angles, XPS, and ATR-FTIR spectra results were carefully recorded to investigate the surface properties of the modified surfaces. It was observed that the functional groups and polar component of surface energy played a pivotal role in long-term modification of PEEK surfaces. The Plasma and PEG Silane treated PEEK surface retained a very low contact angle and high content of hydroxide, carboxylic acid, and peroxide groups as compared to the plasma-treated PEEK surfaces. The lap shear test confirms the long-term effects of Plasma and PEG Silane treatment on adhesion properties with high bonding strength after 48 days of sample storage, which was dropped for Plasma treated surface just after 7 days of storage.

Effect of CF/PEEK plasticity behavior on the mechanical performance of interference‐fit joint

AbstractCarbon fiber reinforced polyetheretherketone polymer (CF/PEEK) thermoplastic composites have a marked plastic yield stage compared to thermoset composites with epoxy matrix. During the interference fit riveting process, extrusion between rivet and composites laminate creates plastic deformation on the hole wall, which will enhance the bearing capacity of composites hole. Therefore, it is expected that the interference fit will play a greater advantage in enhancing the bearing strength of CF/PEEK riveted joint. Numerical and experimental study are applied to investigate the effect of interference fit on bearing strength of CF/PEEK riveted joint. Results show that the plastic deformation of CF/PEEK composites hole wall is positively correlated with the bearing strength of CF/PEEK riveted joint. When the interference fit size exceeds 2.6%, the bearing capacity of CF/PEEK riveted joint reduces because of the increase of fiber damage. It is concluded that the plastic deformation of riveted hole wall can enhance the bearing capacity of CF/PEEK riveted joint, while fiber damage reduces the bearing capacity of CF/PEEK riveted joint. As the increase of interference‐fit size, bearing strength of CF/PEEK riveted joint raises first then decreases, the appropriate interference‐fit size is in the range of 2.0% ~ 2.6%, which is larger than that of thermoset composites.

Effect of different surface treatments on the shear bond strength of PAEKs to composite resin

The present study aimed to evaluate the effects of surface treatment techniques on the shear bond strength (SBS) of Polyetheretherketone (PEEK) and Polyetherketoneketone (PEKK) polymers to composite resin. Eighty-eight rectangular (7 × 7×2 mm) specimens were prepared for each polymer and randomly divided into eight groups (n = 11): untreated (Cnt); treated with non-thermal plasma (Pls); etched with 98% sulfuric acid (Sa); tribochemical silica-coated with Cojet (Tb30); tribochemical silica-coated with Rocatec Plus (Tb110); 98% sulfuric acid + plasma (Sa_Pls); Cojet + plasma (Tb30_Pls); Rocatec Plus + plasma (Tb110_Pls). One specimen from each group was randomly selected for scanning electron microscope analysis. After the bonding agent and an opaquer were applied, composite resin cylinders were built on the specimens. SBS test was performed after water storage, and data were statistically analyzed by 2-way analysis of variance and Tukey’s multiple comparison tests (α = 0.05). The failure-modes were examined. 2-way ANOVA showed that the surface treatment and its interaction between polymer type were significant on SBS values (p < 0.001). Among the PEEK groups, Group Sa (22.55 ± 2.01 MPa) showed the highest SBS value, but no significant difference was observed between Group Tb30, Group Sa_Pls, and Group Tb30_Pls (p > 0.05). Within the PEKK groups, Group Tb30_Pls (22.33 ± 1.19 MPa) showed the highest SBS value, but no significant difference was observed between Group Tb30 and Group Tb110_Pls (p > 0.05). Surface treatments with non-thermal plasma, 98% sulfuric acid and tribochemical silica-coating on PEEK and PEKK increase the bond strength with composite resin. Between the PEEK and PEKK polymers, tested surface treatment effects were significantly different except for the tribochemical silica-coating.

Laser Superficial Fusion of Gold Nanoparticles with PEEK Polymer for Cardiovascular Application.

This paper analyses the possibility of obtaining surface-infused nano gold particles with the polyether ether ketone (PEEK) using picosecond laser treatment. To fuse particles into polymer, the raw surface of PEEK was sputtered with 99.99% Au and micromachined by an A-355 laser device for gold particle size reduction. Biomimetic pattern and parameters optimization were key properties of the design for biomedical application. The structures were investigated by employing surface topography in the presence of micron and sub-micron features. The energy of the laser beam stating the presence of polymer bond thermalisation with remelting due to high temperature was also taken into the account. The process was suited to avoid intensive surface modification that could compromise the mechanical properties of fragile cardiovascular devices. The initial material analysis was conducted by power–depth dependence using confocal microscopy. The evaluation of gold particle size reduction was performed with scanning electron microscopy (SEM), secondary electron (SE) and quadrant backscatter electron detector (QBSD) and energy dispersive spectroscopy (EDS) analysis. The visibility of the constituted coating was checked by a commercial grade X-ray that is commonly used in hospitals. Attempts to reduce deposited gold coating to the size of Au nanoparticles (Au NPs) and to fuse them into the groove using a laser beam have been successfully completed. The relationship between the laser power and the characteristics of the particles remaining in the laser irradiation area has been established. A significant increase in quantity was achieved using laser power with a minimum power of 15 mW. The obtained results allowed for the continuation of the pilot study for augmented research and material properties analysis.

Investigation of in vitro behavior of plasma sprayed Ti, TiO2 and HA coatings on PEEK

Orthopedic implants are one of the most reliable and widely used equipments to increase the quality of human life by enhancing or replacing damaged body parts and ensuring the problematic parts of the body to become operative after a short time period. Polyether ether ketone (PEEK) is a semi-crystal high-performance thermoplastic polymeric implant material which emerged as an alternative for metallic implants that used in orthopedic surgery. Although PEEK has some superior properties such as high melting point, superb wear resistance, excellent fatigue behavior, non-toxicity for bone tissue and elasticity modulus similar to human bone, PEEK has some disadvantages such as biologically inert behavior and low bioactivity. In this context, coating the implant surface to improve its osteointegration behavior is widely accepted. Coating PEEK polymers with bioactive materials such as Hydroxyapatite (HA) is among one of the solutions for this problem. In this study, in order to increase surface bioactivity of PEEK biomaterials, Titanium (Ti), Titanium dioxide (TiO2) and Hydroxyapatite (HA) powder combinations was coated on PEEK samples by using Atmospheric Plasma Spray (APS) method. Morphological and chemical characterization showed produced coatings are suitable for implantation process. Also in vitro tests performed in Simulated Body Fluid (SBF) revealed that HA, Ti + HA and TiO2 + HA coatings have bioactive property.

Nozzle flow characteristics of P.E.E.K (Poly-ether ether ketone) material used in 3D-printing

Abstract Fused deposition modelling (FDM) is one of the predominant processes in additive manufacturing technique in which polymer materials are printed. Polyether ether Ketone (PEEK) is one such polymer which in its pure form has elastic modulus of 4 GPa and its composites have still more higher elastic modulus values of up to 15 GPa. An increased tensile strength of the material and its composites results in increased mechanical strength. The material has higher thermal, chemical stability along with bio compatibility making it suitable for high temperature, corrosive environments and for biomedical applications. The cost of FDM printers using PEEK material is relatively high when compared with other 3D printers. Digital printing of the PEEK polymer material requires special design of the nozzle arrangements along with preheating mechanisms. This is because of the controlled thermal environments required during the printing process. The present work aims at understanding the thermal and fluid flow characteristics of the PEEK material when passing through a commercial nozzle. Experiments are done along with a validated numerical model using COMSOL Multiphysics to avoid thermal degradation of the P.E.E.K material during the melt extrusion process.

Solid Additives and their Lubrication Effects on Polyetheretherketone Polymers – A Review

Solid Additives and their Lubrication Effects on Polyetheretherketone Polymers – A Review

Comprehensive Biological Evaluation of Biomaterials Used in Spinal and Orthopedic Surgery.

Biological acceptance is one of the most important aspects of a biomaterial and forms the basis for its clinical use. The aim of this study was a comprehensive biological evaluation (cytotoxicity test, bacterial colonization test, blood platelets adhesion test and transcriptome and proteome analysis of Saos-2 cells after contact with surface of the biomaterial) of biomaterials used in spinal and orthopedic surgery, namely, Ti6Al4V ELI (Extra Low Interstitials), its modified version obtained as a result of melting by electron beam technology (Ti6Al4V ELI-EBT), polyether ether ketone (PEEK) and polished medical steel American Iron and Steel Institute (AISI) 316L (the reference material). Biological tests were carried out using the osteoblasts-like cells (Saos-2, ATCC HTB-85) and bacteria Escherichia coli (DH5α). Results showed lack of cytotoxicity of all materials and the surfaces of both Ti6Al4V ELI and PEEK exhibit a significantly higher resistance to colonization with E. coli cells, while the more porous surface of the same titanium alloy produced by electron beam technology (EBT) is more susceptible to microbial colonization than the control surface of polished medical steel. None of the tested materials showed high toxicity in relation to E. coli cells. Susceptibility to platelet adhesion was very high for polished medical steel AISI 316L, whilst much lower for the other biomaterials and can be ranked from the lowest to the highest as follows: PEEK < Ti6Al4V ELI < Ti6Al4V ELI-EBT. The number of expressed genes in Saos-2 cells exposed to contact with the examined biomaterials reached 9463 genes in total (ranging from 8455 genes expressed in cells exposed to ELI to 9160 genes in cells exposed to PEEK). Whereas the number of differentially expressed proteins detected on two-dimensional electrophoresis gels in Saos-2 cells after contact with the examined biomaterials was 141 for PEEK, 223 for Ti6Al4V ELI and 133 for Ti6Al4V ELI-EBT. Finally, 14 proteins with altered expression were identified by mass spectrometry. In conclusion, none of the tested biomaterials showed unsatisfactory levels of cytotoxicity. The gene and protein expression analysis, that represents a completely new approach towards characterization of these biomaterials, showed that the polymer PEEK causes much more intense changes in gene and protein expression and thus influences cell metabolism.

Lattice design and 3D-printing of PEEK with Ca10(OH)(PO4)3 and in-vitro bio-composite for bone implant

The addition of biomaterials such as Calcium Hydroxyapatite (cHAp) and incorporation of porosity into poly-ether-ether-ketone (PEEK) are effective ways to improve bone-implant interfaces and osseointegration of PEEK composite. Hence, the morphological effects of nanocomposite on surfaces biocompatibility of a newly fabricated composite of PEEK polymer and cHAp for a bone implant, using additive manufacturing (AM) were investigated. Fused deposition modeling (FDM) method and a surface treatment strategy were employed to create a microporous scaffold. PEEK osteointegration was slow and, therefore, it was accelerated by surface coatings with the incorporation of bioactive cHAp, with enhanced mechanical and biological behaviors for bone implants. Characterization of the new PEEK/cHAp composite was done by X-ray diffraction (XRD), differential scanning calorimetry (DSC), mechanical tests of traction and flexion, thermal dynamic mechanical analysis (DMA). Also, the PEEK/cHAp induced the formation of apatite after immersion in the simulated body fluid of DMEM for differentdays to check its biological bioactivity for an implant. In-vivo results depicted that the osseointegration and the biological activity around the PEEK/cHAp composite were higher than that of PEEK. The increase in the mechanical performance of cHAp-coated PEEK can be attributed to the increase in the degree of crystallinity and accumulation of residual polymer.

Thermal, structural and morphological characterization of dental polymers for clinical applications.

Polymers are used in dentistry on a daily basis due to their mechanical, functional and aesthetic properties. However, such biomaterials are subject to deterioration in the oral environment. Thus, this study aimed to evaluate the structural properties of five commonly used dental polymers to determine their best clinical indications. Four hundred-fifty samples of five dental polymers (polyethylenterephthalat - glycol modified (PG), polymethyl methacrylate (PA), ethylene vinyl acetate(E), polycarbonate (PC), polyetheretherketone (PK) were prepared to investigate their thermal, structural and chemical characteristics using energy dispersive spectroscopy (EDS), Fourier transform infrared analysis(FTIR), scanning electron microscopy (SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), X-ray diffraction(XRD), and Shore D hardness test. Data were analyzed using one-way ANOVA, Tukey's HSD, and Levene's tests (α=0.05). PK (87.2) and PA (82.4) displayed the highest hardness values and smooth surfaces, as observed with SEM (p<0.001). Silica was detected in PK, PA, and E by EDS and XRD. The highest glass transition temperature was recorded for PC (145.00±2.00°C) and PK (143.00±1.87°C), while the lowest value was measured for E (50.00±2.12°C)(p<0.001).The highest mass loss was detected for PG (91.40±1.40%) by TGA. PA and PK polymers can be used for stress-containing treatments due to their mechanical properties. These two materials are also advantageous in terms of plaque accumulation as these polymers reveal smoother surfaces than other groups. Insufficient physical and thermal properties require the use of E with caution and only in limited clinical indications.

Observation of Tribological Wear on PEEK Shaft with Artificial Defect under Radial Rolling Sliding Point Contact

This paper’s aim is to develop the tribological repair method in PEEK (Poly-ether-ether-ketone) polymer mechanical parts with surface damage. The radial rolling sliding contact tests were carried out by using a machined PEEK shaft with an artificial defect as surface damage. An alumina ball and a PTFE composite pin contacted a PEEK shaft specimen under cyclic compressive stress with friction. The particle as solid lubricant from a PTFE composite pin filled up the crevice of the artificial defect. After that, the artificial defect was covered with the deformed microgrooves on the PEEK shaft surface. Due to adhesion by compressive stress and friction, the crevice of the artificial defect was closed. In a running-in process, the artificial defect could be reduced by the adhesion repair.

Interfacial Fracture Toughness Comparison of Three Indirect Resin Composites to Dentin and Polyether Ether Ketone Polymer.

Objectives Advances in laboratory composites and their high wear resistance and fracture toughness have resulted in their growing popularity and increasing use for dental restorations. This study sought to assess the fracture toughness of three indirect composites bonded to dental substrate and polyether ether ketone (PEEK) polymer. Materials and Methods This in vitro study was conducted on two groups of dental and polymer substrates. Each substrate was bonded to three indirect composite resins. Sixty blocks (3 × 3 × 12 mm) were made of sound bovine anterior teeth and PEEK polymer. Sixty blocks (3 × 3 × 12 mm) were fabricated of CRIOS (Coltene, Germany), high impact polymer composite (HIPC; Bredent, Germany), and GRADIA (Indirect; GC, Japan) composite resins. Composites were bonded to dentin using Panavia F 2.0 (Kuraray, Japan). For bonding to PEEK, Combo.lign (Bredent) and Visio.Link (Bredent) luting cements were used. In all samples, a single-edge notch was created by a no. 11 surgical blade at the interface. The samples were subjected to 3,500 thermal cycles, and their fracture toughness was measured in a universal testing machine (Zwick/Roell, Germany) by application of four-point flexural load. Statistical Analysis Data were analyzed using one-way analysis of variance, Kruskal–Wallis. Results The fracture toughness of CRIOS–PEEK interface was significantly higher than HIPC–PEEK. The fracture toughness of GRADIA–PEEK was not significantly different from that of HIPC and CRIOS. The fracture toughness of GRADIA–dentin was significantly higher than HIPC–dentin. Conclusion Considering the limitations of this study, GRADIA has the highest bond strength to dentin, while CRIOS shows the highest bond strength to PEEK.

Lifting Lightweight Metals to a New Level—Tribological Improvement by Hybrid Surface Solutions on Aluminium and Magnesium

Nanocrystalline PEO (plasma electrolytical oxidation) coatings were performed on Al 6082 and Mg AZ31 alloys, resulting in hard, dense and wear-resistant surfaces to increase the wear resistance of those alloys. To soften the wear influence on the counter body side and to reduce friction in a tribological application, the high-performance polymer PEEK (poly-ether-ether-ketone) was added to the load-supporting PEO surface by a laser melting technique to avoid heat influence on the lightweight substrate. The usage of additives in the PEEK dispersion led to stable conditions in the tribological system by decreasing the wear on the coated substrate as well as the counter body to a minimum accompanied by a low coefficient of friction during the whole life-time. The adopted hybrid coating systems were characterized using laser scanning microscopy (LSM), secondary and back scattered electron microscopy (SEM) and energy dispersive spectroscopy (EDS). A pin-on-disc test was employed to analyze the wear behavior of the different PEO and hybrid coatings and the influences of these surfaces on the coefficient of friction.

An atomistic view of heat propagation from graphene to polyether ether ketone (PEEK)

Graphene is a two-dimensional form of carbon that has shown outstanding potential as an additive to polymer composites. Polyether ether ketone (PEEK) is a thermoplastic polymer that has been used extensively in industrial applications due to its high temperature stability, as well as other mechanical and chemical properties. In this study, we model a scenario where the graphene in a PEEK-graphene composite is heated, and then observe the response of PEEK polymer chains to the heat generated by graphene. Studying heat transfer from graphene to PEEK, as well as the effect of changes in the local chemistry at the interface between both materials, can improve the understanding of the performance of high-temperature graphene-PEEK. Using molecular dynamics and ab initio simulations, it is determined that as graphene in the composite is heated, the extent of the interfacial region between the two components changes. These changes affect the range of interactions at the interface as well as the efficiency of heat transfer. The number of graphene layers appears to play a significant role in the change in the interfacial region. Unlike monolayer and hexalayer graphene-PEEK configurations, bilayer graphene-PEEK configuration shows a decrease in the extent of the interfacial region at low temperatures, an indication of a more efficient heat transfer. The addition of approximately 5% hydroxyl functionalization of the surface of the graphene translated into a significant increase in the heat transfer.

Resistencia a la flexión del poliéter éter cetona poliéter de alto rendimiento en comparación con la aleación de metal base y la cerámica de circonio

Optimal flexural strength is a critical prerequisite for prosthetic frameworks. This study aimed to assess the flexural strength of polyether ether ketone (PEEK) polymer compared to a base metal alloy and high-strength Zirconia ceramic commonly used in prosthodontic treatments. Materials and Methods: In this in vitro, experimental study, 10 bar-shaped samples measuring 18×5×2mm were fabricated of each the PEEK polymer, nickel-chromium base metal alloy and zirconia ceramic. Half of the samples in each group were subjected to 5000 thermal cycles between 5°C - 55°C with 20 seconds of dwell time and 20 seconds of transfer time to simulate oral conditions. All samples then underwent three-point bending test. Two-way ANOVA followed by Tukey’s test were applied to compare the mean flexural strength of the groups with and without thermocycling at 0.05 level of significance. Results: The flexural strength of base metal alloy, Zirconia and PEEK was 1387.70±45.50 MPa, 895.13±13.99 MPa and 192.10±5.37 MPa, respectively. The difference was significant among the groups (p&lt;0.001). Thermocycling had no significant effect on the flexural strength of samples in any group (p=0.306). Conclusion: PEEK high-performance polymer had a lower flexural strength than base metal alloy and Zirconia ceramic, and its flexural strength was not affected by thermocycling. PEEK seems to be able to resist masticatory forces in the oral cavity pending further in vitro and clinical studies.