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In the present study, the feasibility to achieve localized induction heating and debonding of multi-material composite structures is assessed in testing coupons prepared by Automated Fiber Placement (AFP) and extrusion-based additive manufacturing (AM) technologies. Nano-compounds of Polyether-ketone-ketone (PEKK) with iron oxide nanoparticles acting as electromagnetic susceptors have been processed in a parallel co-rotating twin-screw extruder to produce filament feedstock for extrusion-based AM. The integration of nanocomposite interlayers as discrete debonding zones (DZ) by AFP-AM manufacturing has been investigated for two types of sandwich-structured laminate composites, i.e., laminate-DZ-laminate panels (Type I) and laminate-DZ-AM gyroid structures (Type II). Specimens were exposed to an alternating magnetic field generated by a radio frequency generator and a flat spiral copper induction coil, and induction heating parameters (frequency, power, heating time, sample standoff distance from coil) have been investigated in correlation with real-time thermal imaging to define the debonding process window without compromising laminate quality. For the optimized process parameters, i.e., 2–3 kW generator power and 20–25 mm standoff distance, corresponding to magnetic field intensities in the range of 3–5 kA m−1, specimens were effectively heated above PEKK melting temperature, exhibiting high heating rates within the range of 5.3–9.4 °C/s (Type I) and 8.0–17.5 °C/s (Type II). The results demonstrated that localized induction heating successfully facilitated debonding, leading to full unzipping of the debonding zones in both laminate structures. Further insight on PEKK nanocomposites debonding performance was provided by thermal, morphological characterization and non-destructive inspection via X-ray micro-computed tomography at different processing stages. The developed framework aims to contribute to the development of rapid, on-demand joining, repair and disassembly technologies for thermoplastic composites, towards more efficient maintenance, repair and overhaul operations in the aviation sector and beyond. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) enables the automated production of complex geometries with low waste and lead time, notably through Material Extrusion (MEX). This study explores Large Format Additive Manufacturing (LFAM) with carbon fiber-reinforced polyaryletherketones (PAEK), particularly a slow crystallizing grade by Victrex. The research investigates how extrusion parameters affect the mechanical properties of the printed parts. Key parameters include line width, layer height, layer time, and extrusion temperature, analyzed through a series of controlled experiments. Thermal history during printing, including cooling rates and substrate temperatures, was monitored using thermocouples and infrared cameras. The crystallization behavior of PAEK was replicated in a Differential Scanning Calorimetry (DSC) setup. Mechanical properties were evaluated using three-point bending tests to analyze the impact of thermal conditions at the deposition interface on interlayer bonding and overall part strength. The study suggests aggregated metrics, enthalpy deposition rate and shear rate under the nozzle, that should be maximized to enhance mechanical performance. The findings show that the common practice of setting fixed layer times falls short of ensuring repeatable part quality. [ABSTRACT FROM AUTHOR]

The present work deals with the effect of Multi-walled Carbon Nanotube (MWCNT) and functionalized (carboxyl and amine) MWCNT on the mechanical properties of the PAEK (Poly Aryl Ether Ketone) polymer composite. The MWCNT and functionalized (carboxyl and amine) MWCNT concentration varied as 0.25, 0.5 and 0.75 weight percentages. Compositeswere prepared by using a melt compounding method using a twin-screw extruder and all testing samples were prepared using an injection molding machine as per American Society for Testing and Materials (ASTM) standards. Samples were tested for tensile strength, impact strength, flexural strength, heat deflection temperature, hardness, and density. There is an increase in the tensile strength, impact strength, flexural strength, and heat deflection temperature, with percentage increase in filler loading up to 0.5 %, followed by decrease in it with higher filler loading. The increase is maximum for amine functionalized MWCNT.

Regarding the dynamic development of 3D printing technology, as well as its application in a growing part of industries, i.e., in the automotive industry, construction industry, medical industry, etc., there is a notable opportunity for its application in producing dental implants, which presents a promising alternative to traditional implant manufacturing methods. The medical industry is very restrictive regarding the applied materials, and it is necessary to use materials that exhibit very good mechanical and thermal parameters, show clinical indifference and biocompatibility, are non-allergenic and non-cancerous, and are likely to sterilize. Such materials are poly(aryl-ether-ketone)s (PAEK)s, mainly poly(ether-ether-ketone) (PEEK) and poly(ether-ketone-ketone) (PEKK), that are found to be high-performance polymers and can be defined as materials that retain their functionality even in extreme conditions. In the present paper, two types of PEEKs and PEKK were compared regarding their structural, mechanical, and thermal properties along with the biological activity toward selected strains. The tested samples were obtained with Fused Deposition Modeling (FDM) technology. The PEKK, after heat treatment, exhibits the most promising mechanical properties as well as less bacterial adhesion on its surface when compared to both PEEKs. Consequently, among the evaluated materials, PEKK after heat treatment stands out as the optimal selection for a dental prosthesis. [ABSTRACT FROM AUTHOR]

The growing use of thermoplastic composites in aviation, automotive, sports and medical industries is forcing the development of processing technology. Due to the properties of thermoplastic composite materials, their shaping is subject to many restrictions. For this reason, it is not always possible to obtain components with complex geometry and adequate quality. By using numerical analysis and experience in the production of parts using hot pressing technology, we are able to predict the course of the process and the behaviour of the material during formation. The article describes how to build a model for numerical analysis of the process of thermoforming monolithic inspection door stiffening for an ILX-34 aircraft using a Toray Cetex® TC1225 carbon composite material with a thermoplastic polyaryletherketone (PAEK) matrix. Pam-Form v2019.0 software version V1.9.N was used for modelling. The results of the analysis were compared with those of the part produced by the Institute of Aviation, Łukasiewicz Research Network. [ABSTRACT FROM AUTHOR]

(1) Background: The use of high-performance polymers for fixed restorations requires additional studies regarding their adaptability and processing with CAD/CAM technology. This in vitro study aims to assess the marginal and internal fit of PEEK and PEKK materials using microcomputed tomography. (2) Methods: Twenty-four (n = 8) MOD onlays made of PEKK (Pekkton ivory), unmodified PEEK (Juvora medical), and modified PEEK (BioHPP) were investigated. A typodont mandibular left first molar was scanned to achieve 24 resin, 3D printed abutment teeth. The onlays were fabricated with a five-axis milling machine, and after cementation of the specimens, the marginal (MG) and internal gaps (IG) were evaluated at twelve points in the mesio-distal section and thirteen points in the bucco-lingual section using microcomputed tomography. For statistical data analysis, Wilcoxon signed-rank/paired Student t-Test, Mann–Whitney/unpaired Student t-Test, and one-way ANOVA test were applied. (3) Results: Significant differences (p < 0.05; α = 0.05) were reported between the MG and IG for each material for all three polymers and also among two materials in terms of the MG and IG (except Juvora-BioHPP). The highest IG values were recorded in angular areas (axio-gingival line angle) in the mesio-distal section for all the polymers. (4) Conclusions: For all the materials, MG < IG. The type of polymer influenced the adaptability; the lowest marginal and internal gap mean values were recorded for BioHPP. The analyzed polymer used for onlays are clinically acceptable in terms of adaptability. [ABSTRACT FROM AUTHOR]

The microbiological behavior of dental polymer materials is crucial to secure the clinical success of dental restorations. Here, the manufacturing process and the machining can play a decisive role. This study investigated the bacterial adhesion on dental polymers as a function of manufacturing techniques (additive/subtractive) and different polishing protocols. Specimens were made from polyaryletherketone (PEEK, PEKK, and AKP), resin-based CAD/CAM materials (composite and PMMA), and printed methacrylate (MA)-based materials. Surface roughness (Rz; Ra) was determined using a laser scanning microscope, and SFE/contact angles were measured using the sessile drop method. After salivary pellicle formation, in vitro biofilm formation was initiated by exposing the specimens to suspensions of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Adherent bacteria were quantified using a fluorometric assay. One-way ANOVA analysis found significant influences (p < 0.001) for the individual parameters (treatment and material) and their combinations for both types of bacteria. Stronger polishing led to significantly (p < 0.001) less adhesion of S. sanguinis (Pearson correlation PC = −0.240) and S. mutans (PC = −0.206). A highly significant (p = 0.010, PC = 0.135) correlation between S. sanguinis adhesion and Rz was identified. Post hoc analysis revealed significant higher bacterial adhesion for vertically printed MA specimens compared to horizontally printed specimens. Furthermore, significant higher adhesion of S. sanguinis on pressed PEEK was revealed comparing to the other manufacturing methods (milling, injection molding, and 3D printing). The milled PAEK samples showed similar bacterial adhesion. In general, the resin-based materials, composites, and PAEKs showed different bacterial adhesion. Fabrication methods were shown to play a critical role; the pressed PEEK showed the highest initial accumulations. Horizontal DLP fabrication reduced bacterial adhesion. Roughness < 10 µm or polishing appear to be essential for reducing bacterial adhesion. [ABSTRACT FROM AUTHOR]

Some specialty polymers such as polyetheretherketone (PEEK), Polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyamideimide (PAI), and polyimide (PI) are the ideal choices for developing high performance bidirectionally reinforced composites that would excel in specific strength performance. However, these polymer composites are extremely challenging from a processing point of view and have limited choices. Most of the time, a lot of compromises are to be made on the fiber-matrix wetting issues. The current research elaborated on a method to exploit two techniques together to opt for advantages from both. Polyetherimide (PEI) solutions of various concentrations/viscosities were used as sizing agents for the fibers so as to wet the cross-over points on graphite fabric and inter-tow filaments. It was expected that the PEI and PAEK would form a blend at the interface, although fiber would necessarily be covered with only PEI. It was also anticipated that there could be an optimum amount of PEI on the fibers’ surface for the best performance properties. Based on the in-depth studies on the performance properties, it was concluded that PEI solution in the range of 5–10 wt. % would lead to the best combination of performance properties. Compared to the classical method of developing PAEK-graphite fabric composites by film technique, the current method of combination of impregnation and film technique led to excellent results.

In a context of ecological transition, aeronautics is moving towards the development of hydrogen-powered aircraft for which lightweight, long-lasting and tough storage tanks must be developed. Among other properties, the tightness of tanks made of polymer and composite materials is of prime importance. This study thus aims at understanding the permeation phenomena through Poly-Ether-Ketone-Ketone (PEKK), which is one of the thermoplastic polymers considered for tank manufacture. In order to better understand the phenomena governing gas permeability, tests were carried out on different PEKK grades of different T/I ratios and degree of crystallinity. The results show that the crystallinity ratio is not the only factor that governs gas diffusion and solubility, but that permeability also depends on PEKK semi-crystalline microstructure. Even if considering crystallites organization through a tortuosity factor improves permeability predictions, permeability can be better understood using a 3 phases description of PEKK microstructure considering distinct contributions of the rigid and mobile amorphous fractions (RAF and MAF). It appears that the MAF permeation does not depend on PEKK T/I ratio, but that gas diffusion and solubility increase for RAF when increasing T/I ratio, thus counterbalancing the blocking effect of crystallites. [Display omitted] • The permeability of PEKK grades does not depend directly on the degree of crystallinity. • The T/I ratio of PEKK affects the barrier properties of the amorphous phase. • Distinct contributions of PEKK's mobile and rigid amorphous fractions to permeability. • Identical behavior of mobile amorphous phase regardless of PEKK grade. • Greater diffusion in the rigid amorphous phase than in the mobile amorphous phase. [ABSTRACT FROM AUTHOR]

This investigation highlights argon plasma treatment on Poly-aryl-ether-ketone (PAEK) and carbon fibre (CF) surface. The PAEK and CF surface is modified for 300 sec and the change in physiochemical and mechanical properties were investigated through Fourier Transform Infrared Spectroscopy (FTIR), Dynamic Contact angle, Atomic Force Microscope (AFM) and Tensile Test. FTIR of surface modified PAEK revealed the stretching of C-H, C=C and C=O functional groups. A reversal phenomenon of increased surface energy was observed through dynamic contact angle study of CF and to further examine the surface energy effect, AFM analysis on CF was carried out revealing increased roughness with numerous micro dents formation. PAEK/CF composite samples were fabricated through compression moulding technique. The change in mechanical properties due to surface modification were analysed through Tensile testing on surface modified PAEK/CF sample and untreated PAEK/CF samples. The surface treated PAEK/CF showed increased tensile strength than untreated PAEK/CF. The argon plasma treatment helped in creating depth striations that lead to better interlocking of resin matrix with the reinforced CF. The fracture surface was examined through Filed Emission Scanning Electron Microscope (FE-SEM) wherein the Micrographs of the tensile tested samples indicated failure of composite due to fibre breakage. [ABSTRACT FROM AUTHOR]

Introduction of metal-free restoration has always been a hot topic of research in the field of dentistry. Polyetheretherketone (PEEK), a polymer that is metal-free and with the similarity of modulus of elasticity with bone and dentin makes it a suitable material. In the past 2-3 years, it has gained a lot of popularity in prosthodontics however it has not been studied in depth. So the purpose of this review is to summarize the outcome of the various research conducted on this material so as to undeinvolve the following sequencerstand it in a better way and to popularize its use in clinical application. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of artificial aging on the Martens parameters of different 3D printed and milled polyaryletherketon (PAEK) materials. In total 120 specimens of 4 different polyetheretherketon (PEEK) materials (Essentium PEEK, KetaSpire PEEK MS-NT1, VICTREX PEEK 450 G and VESTAKEEP i4 G) were additively manufactured via fused layer manufacturing (FLM) in either horizontal or vertical directions (n = 15 per group). 75 specimens were milled out of prefabricated PAEK blanks from the materials breCAM.BioHPP, Dentokeep, JUVORA Dental Disc 2 and Ultaire AKP (= 15 per group). Martens hardness (HM), indentation hardness (H IT) and indentation modulus (E IT) were determined initially and longitudinally after thermocycling (5−55 °C, 10,000x) and autoclaving (134 °C, 2 bar). In each case, the surface topography of the specimens was examined for modifications using a light microscope. Data were analysed with Kolmogorov-Smirnov test, univariate ANOVA followed by post-hoc Scheffé test with partial eta squared (η p 2), Kruskal–Wallis-, Mann–Whitney-U-, Friedman- and Wilcoxon-Test. A value of p < 0.05 was considered as significant. Milled specimens showed higher Martens parameters than printed ones (p < 0.001). Artificial aging had a negative effect on the measured parameters (p < 0.001). Horizontally printed specimens presented higher Martens parameters than vertically printed ones, regardless of material and aging process (p < 0.001). Essentium PEEK and breCAM.BioHPP showed the highest and VICTREX PEEK 450G as well as Ultaire AKP the lowest values of all investigated PAEK materials initially, after thermocycling and after autoclaving (p < 0.001). Microscopic examinations showed that artificial aging did not cause any major modifications of the materials. Additively manufactured PEEK materials showed lower Martens parameters than milled ones, whereas horizontally printed specimens presented higher values than vertically printed ones. Artificial aging had a negative effect on the Martens parameters, but not on the surface topography. [ABSTRACT FROM AUTHOR]

The paper reports on the comparative potential of nano-particles and micro-particles of mica in glass fiber reinforced Polyaryletherketone (PAEK) composite containing graphite (10 wt%). Very high PV limit value (>100 MPa-m/s), very low specific wear rate (K 0) (2–∼8 × 10−16 m3/Nm) along with very low friction coefficient (μ) (0.04–0.08), were exhibited by the composites. The PV limit values of a nano-composite (NC) and micro-composite were 126 and 84 MPa m/s respectively. Friction and wear performance of a nono-composite was significantly better at lower PV conditions (40% lower in wear rate and 20% in friction). Worn surfaces were studied by scanning electron microscopy (SEM) and 3D profilometer, while the interaction of the constituents with a disc surface was investigated with the X-ray photoelectron spectroscopy (XPS). • Nano-particles (NPs) of mica were first time explored in PAEK tribo-composite. • Nano-particles of mica proved more beneficial as lubricant than the micro-particles. • High PV limit (112 MPa m/s) with very low μ and wear was reported by nanocomposite. • 27% improvement in wear and 16% in μ due to NPs compared to micro-particles. [ABSTRACT FROM AUTHOR]

Abstract Hexagonal boron nitride (hBN), also called as white graphite is known to exhibit excellent combination of thermal, thermo-physical, mechanical and tribological properties as a filler (solid lubricant). Not much reported on its potential as nano-particles. In this study, micro and nanocomposites of hBN were prepared with the combination of polyaryl ether ketone (PAEK) as a matrix (50%), short glass fibers (GF) (30%) as a reinforcement and natural graphite (10%) as a primary solid lubricant (SL) apart from hBN particles (10%) as a secondary SL. The micro-composite (MC) and nano-composite (NC) contained hBN particles in micron size and combination of micron and nano size (7 and 3%) respectively. The NC exhibited enhanced mechanical and tribological performance compared to the MC. Tribological tests were performed on a pin-on-disc tribometer under dry sliding regime to evaluate PV limit (pressure x velocity) values. Influence of load and sliding speed on the friction coefficient (μ) and specific wear rate (K 0) on the composites was investigated. The composites showed PV limit of 100 MPa m/s along with μ in the range of 0.04–0.08 and K 0 in the range of 2.5–7 × 10− 16 m 3 /Nm. It was also found that the superior performance of NC was due to more efficient, thin and coherent film transferred on the disc. Moreover, structural and morphological changes were studied with Raman spectroscopy and scanning electron microscopy (SEM). Wear mechanism of the worn surfaces were discussed using XPS (X-ray photoelectron spectroscopy). Highlights • Hexa boron nitride (hBN) showed better lubricating characteristics in combination with graphite. • The glass fibers were oriented along the direction of polymer melt which was explained by X-ray tomography. • Nano-hBN and graphite has synergistic effect on improving tribological behavior and PV limit of composites up to 100 MPa m/s. [ABSTRACT FROM AUTHOR]

In recent times, polymer-based biocomposites are being pitched as the future of biomedical materials for implant and prosthesis development. PAEK (Polyaryletherketone) is one such viable thermoplastic and a member of the PEKs (Polyetherketones) family, of which many homologues have already been established for biomedical applications. In this study, atomistic models of PAEK-based biocomposite with HAp (Hydroxyapatite) as reinforcement have been developed. HAp is well-known bioceramic for its similar chemical structure to that of a natural bone's inorganic conformation and thus is used to induce biocompatibility. Atomistic model for different weight concentrations of HAp i.e. 0%, 1%, 3%, 5%, 7%, and 9% are developed to understand the effects of HAp reinforcement in PAEK matrix. Since, mechanical properties are one of the most prominent parameters for the development of an implant material as they should be in the range of human bone to avoid stress-shielding. The mechanical behavior of the PAEK/HAp biocomposites have been investigated via molecular dynamics simulation. Elastic properties were determined at constant strain rate and the stress strain behavior was simulated for both tension and compression separately at 298K. The simulation results shows significant increase in ultimate tensile (2.54 times) and ultimate compressive strength (1.69 times) of biocomposite with incorporation of HAp (max at 7%). Although proportional increase in brittleness to the weight content of HAp was also observed. The study provides an approach to analyze PAEK/HAp biocomposites and concludes that this combination is a potential alternative to contemporary implant materials. • PAEK has superior properties than PEEK yet still under-researched homologue of PEKs family. • Atomistic models of PAEK-based biocomposite with HAp as reinforcement have been developed for first time. • Different weight concentrations of HAp i.e. 0%, 1%, 3%, 5%, 7%, and 9% were taken in the study. • The mechanical behavior of the PAEK/HAp biocomposites were investigated via MD simulations. • A notable increase in ultimate tensile and compressive strength of biocomposite was found with mixture of 7% HAp. [ABSTRACT FROM AUTHOR]

A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the high conductivity associated with the pendant API group. The chemical structure of QPECH/PAEK-API membranes was identified by 1H nuclear magnetic resonace spectroscopy. A variety of membrane properties, such as anion conductivity, water uptake, length swelling percentage, and thermal, mechanical and chemical stability, were investigated. The QPECH/PAEK-API1 membrane showed quite high hydroxide ion conductivity, from 0.022 S cm−1 (30 °C) to 0.033 S cm−1 (80 °C), and excellent mechanical strength, associated with the low water uptake of less than 40%, even at 80 °C. Such high conductivity at relatively low water uptake is attributed to the concentrated cationic groups, in a cross-linked structure, facilitating feasible ion transport. Further, the QPECH/PAEK-API membranes showed thermal stability up to 250 °C, and chemical stability for 30 days in a 4 NaOH solution, without significant loss of ion exchange capacity.

Abstract While designing the ambitious advanced composites based on PAEK (50 wt%), glass fibers (30 wt %) and natural graphite (10 wt %), it was proposed to include one more solid lubricant (10 wt %) from the category of metal chalcogenides. Particles of MoS 2 and WS 2 in micron and nano-sizes were selected for inclusion in combination with natural graphite. The themes for investigations were; which one is the better performer amongst MoS 2 and WS 2 , and nano-particles can impart beneficial effect or not; and the last how efficient would be these tribo-composites in terms of friction, wear resistance and PV limit values. The composites were characterized in detail for physical, mechanical, thermal and tribological performance. The WS 2 proved more beneficial till moderate PV conditions but not for severe conditions as compared to MoS 2. The composites proved excellent tribo-materials in terms of low friction (∼0.04), wear rate (2.2 × 10−16 MPa m/s) and PVsafe values (84 MPa m/s). The chemistry of the counterface surface was studied using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (RS) while the morphology of the worn pins surface and counterface surface was observed using a combination of 3D profilometer and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

In this study, the Taguchi method was utilized to optimize fused filament fabrication (FFF) additive manufacturing with the goal of maximizing the flexural strength of 3D printed polyaryletherketone specimens. We analyzed 3D printed (3DP) carbon fiber reinforced poly-etherketoneketone (CFR PEKK), 3D printed and pressed (3DP + P) CFR PEKK, and injection molded medical grade polyetheretherketone (PEEK) as a control. Fracture surfaces were analyzed via scanning electron microscopy (SEM). The parameters that were varied in the optimization included nozzle diameter, layer height, print speed, raster angle, and nozzle temperature. We analyzed the flexural strength and flexural modulus determined from 3-point bending (ASTM D790). Using Taguchi optimization, the signal to noise ratio (SNR) was calculated to determine the relationship between the input parameters and flexural strength and to determine optimal print settings. Results were confirmed with analysis of variance (ANOVA). The raster angle and layer height were determined to have the greatest impact on the flexural strength of specimens printed in the FFF process for 3DP CFR PEKK. The optimized printing parameters were found to be 0/90 Raster Angle, 0.25 mm layer height, 0.8 mm Nozzle Diameter, 375 °C nozzle temperature, and 1100 mm/min print speed. The optimized 3DP CFR PEKK test samples had a flexural strength of 111.3 ± 5.3 MPa and a flexural modulus of 3.5 GPa. 3DP + P CFR PEKK samples had a flexural strength of 257.2 ± 17.8 MPa and a flexural modulus of 8.2 GPa. Statistical comparisons between means demonstrated that pressing significantly improves both flexural strength and flexural modulus of 3DP CFR PEKK. The results of this study support the hypothesis that post consolidation of 3DP specimens improves mechanical properties. Post-processing composites via pressing may allow greater design freedom within the 3DP process while improving mechanical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

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Improving the energy efficiency of mechanical systems and reducing the usage of lubricant oils and related additives are challenging tasks of the 21st century. Consequently, the application of tribopolymers increases due to their easy processing (injection moulding) and lower density (mass reduction). Among them are the poly(ether-ether-ketone) (PEEK) and the poly(aryl-ether-ketone) (PAEK) with outstanding mechanical properties, and poly(tetrafluorethylene) (PTFE), a solid lubricant. This work produced powder-like PAEK + PTFE blends (2%–30% PTFE) by low and high-energy grinding processes; then, the specimens were shaped by hot pressing. The morphology and composition of the post-grinding particles were analysed by white light interferometry (WLI), scanning electron microscopy (SEM) and X-ray dispersive energy spectroscopy (EDS). The fractography and thermal analysis of the specimens were performed via SEM-EDS and differential scanning calorimetry (DSC). For tribological evaluation, reciprocating (2Hz, 10 mm) cylinder-on-flat tests were conducted to determine the lubricious regime duration, the friction coefficient (COF) during the steady-state regime, and wear rates, where the worn volumes (specimen and counterbody) were measured by WLI. High-energy grinding leads to smaller and more plastically deformed particles. In addition, the incorporation of PTFE into PAEK is more homogeneous with a higher crystalline degree. The self-lubricating effect is manifested from 5% of PTFE, and the best results are reached for 15% of solid lubricant, with an average wear rate of 9.4 × 10−16 mᶟ/Nm and COF of 0.08, against 5.3 × 10−14 mᶟ/nm and 0.32 for pure PAEK, respectively. • The two mixing methods used to produce the blend (PAEK + PTFE) resulted in completely different blends structural morphology. • But high energy method induces the formation of polymers with higher crystallinity degrees. • Higher tribological performance was reached from 5% of PTFE concentration. [ABSTRACT FROM AUTHOR]

Advanced engineering polymers of the polyaryletherketone (PAEK) family with carbon fibre reinforcement are finding application in engineering systems as tribological bearing surfaces under severe operating conditions that cyclically move the polymer into and beyond the glass transition temperature region. To support such an application, the friction in high-speed and low-load PAEK-steel sliding contacts was investigated both unlubricated and lubricated with a trinonyl trimellitate ester, a base fluid for high temperature industrial lubricants. Four polymers in the PAEK family, PEEK, PEK, PEKEKK and PEKK, with 30 wt% of carbon fibre whiskers were tested against an AISI 4140 steel disc. When unlubricated, low friction depended upon the formation of a PAEK transfer film on the steel disc and when this became unstable in the glass transition region the friction increased to much higher levels with associated polymer surface damage. Frictional heating due to the high sliding speed dominated the differences in glass transition behaviour between the four PAEKs. When lubricated, the lubricant film controlled friction and there was no significant effect of the glass transition of any of the PAEKs. The irreversible nature of the glass transition in PAEKs in such tribological applications, due to high surface damage at high temperature, means that it is essential to ensure effective lubrication in both fluid film and boundary lubrication. [ABSTRACT FROM AUTHOR]

A novel type of graphite (thermographite) having higher thermal conductivity (TC) due to a patented treatment is commercialized recently. It was anticipated that such particles would be more effective in conducting away frictional heat generated on the tribo-surfaces leading to the enhanced performance. Hence two composites were developed based on high performance Polyarylether ketone (PAEK) (50% by wt) containing 30% short glass fibers (GF) and hexa-boron nitride (hBN) 10% apart from 10% graphite. First composite designated as C NG contained 10% natural graphite (NG) while the other designated as C TG contained 10% thermographite (TG). These were processed by identical method (twin screw extrusion followed by injection molding). The tribo-performance was evaluated in a pin on disc (mild steel) configuration under very high load and speeds. It was observed that both the composites exhibited excellent tribo-performance. However, C NG performed better than the C TG in all respects only under severe operating conditions. Under low PV conditions, difference was not clear. It showed lower friction coefficient, and wear rate as compared to C TG . C NG showed PV limit value 96.6 MPa-m/s which was decisively superior to C TG (91 MPa-m/s). C NG could sustain higher speed (3.45 m/s) than the C TG (3.25 m/s) under 900 N in spite of slightly lower TC. It was concluded that during treatment (patented by the company) TG has slightly distorted layer-lattice structure as compared to the natural graphite, which could be responsible for transferring less beneficial film under severe operating conditions. SEM and EDAX studies were conducted to understand wear mechanisms. Such composites with such high PV limit values low, µ (0.04) and low wear rates (1×10 − 16 m 3 /Nm) are not reported in the literature and may prove as ideal materials for dry bearings in harsh operative conditions. [ABSTRACT FROM AUTHOR]

Two kinds of phthalonitrile end-capped poly (aryl ether ketone) oligomers (CN-o-PEEK and 2CN-o-PEEK) have been synthesized. The two molecular structures were identified using Fourier transform infrared, nuclear magnetic resonance, and elemental analysis. Hydroxy-containing CN-o-PEEK can be thermal polymerized by duration at 225°C for various times, even in the absence of curing additives. Char yields at 800°C after heat treatment for 60 min were 55%. 2CN-o-PEEK was cured in the presence of p-bis[4-(4-aminophenoxy) phenyl]sulfone via heating its powders up to 275–375°C. The synthesized oligomers have good solubility, whereas the cured samples become insoluble in common organic solvents. The resulting cured samples exhibit no glass transition temperature up to 400°C as measured by differential scanning calorimetry and possess excellent thermal stability. [ABSTRACT FROM AUTHOR]

In the present research, the synthesis and characterization of poly(arylene ether ketone) (PAEK)–cadmium sulfide (CdS) nanocomposites prepared using carboxylic-functionalized PAEK (PCA-PAEK) as the ligand in dimethylformamide solution from cadmium acetate and thiourea is reported. The resulting CdS/PCA-PAEK nanocomposites were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, ultraviolet–visible (UV-vis) spectroscopy, and photoluminescence (PL) spectroscopy, confirming the formation of CdS quantum dots (QDs) with small particle size. The results of PL measurement showed that the nanocomposite exhibited distinct luminescence properties. Furthermore, the effects of reaction time, CdS/PCA-PAEK ratio, and Cd2+/thiourea ratio on the PL of CdS QDs were also investigated. Thus, a novel simple route was successfully developed for synthesizing nanohybrids based on QDs and high-performance polymers with incorporated carboxylic moiety. [ABSTRACT FROM PUBLISHER]

Abstract: This study is focused on performing tribological tests on new materials for orthopaedic implants applications, PAEK (poly aryl ether ketone) polymer group. The experiments were performed in physiological liquid, at 37°C, for simulating the human body fluid. PAEK''s tribological properties that are wear rate of polymers and wear mechanisms on common metallic alloys used as orthopaedic implants: Co–Cr, 316L SS and Ti–6Al–4V are compared to the gold standard used for hip joint prosthesis, the UHMWPE (ultra high molecular weight polyethylene) on the same metal alloys. PEEK (poly ether ether ketone) and PEKK (poly ether ketone ketone)/CF (carbon fibers) show the lowest wear rate on every counter metallic material; the system UHMWPE on any metal alloys exhibit the highest wear rate although having the lowest friction coefficient. From microscopic images and the evolution of the friction coefficient, a wear mechanism was suggested for each polymeric material. [Copyright &y& Elsevier]

In the current study, the potential of MWCNTs (functionalized with hydroxyl group) was explored for enhancing the performance properties of a high-performance polymer matrix, i.e., polyetherketoneketone (PEKK). The dispersion and distribution of MWCNTs (0, 0.1, 0.3, 0.5, and 1 wt %) were ensured by rigorous probe-ultra sonication and confirmed with FESEM (Field Emission-Scanning Electron Microscopy). The nano-composites and their surfaces were characterized for physical, thermal, and mechanical properties, including tensile strength, micro-hardness (Scratch and Vickers's), lap shear strength (LSS), contact angle, surface free energy and friction. MWCNTs led to reduction in friction but enhancement in mechanical properties. It was concluded from the studies that the addition of MWCNTs at 0.3 wt % led to best combination of performance properties such as LSS, tensile strength and modulus, micro-hardness, etc. The current study concluded that among the three effects offered by MWCNTs in the adhesives on LSS viz. reinforcement (a positive one), increasing interfacial adhesion with the adherend (a positive one) and friction–reducing (a negative one), the first two overweighed the third one significantly and led to a net improvement in LSS. It was also concluded that PEKK proved to have highest LSS followed by PAEK (Polyaryletherketone) and then PEEK (polyetheretherketone). Their nanocomposites also showed the same trend. [Display omitted] • Maiden approach to achieve good dispersion & distribution of MWCNTs in PEKK, PAEK PEEK. • Amount optimization of MWCNTs for best performance. • Significant performance improvement in nano-composites and nano-adhesives. • Effect of variation of matrices on lap shear strength of nano-adhesives. • Validation of various theoretical models for PEKK-MWCNT nano-composites. [ABSTRACT FROM AUTHOR]

The PEKK material can be used in prosthodontics for framework manufacturing and is commonly laminated with veneering composites to achieve a better esthetics. Various surface treatment methods including sandblasting, etching, laser and cold plasma treatments were reported to enhance the adhesive properties of dental polymers. Both tensile and shear bond test were employed to quantify the bond strength between PEKK and veneering composites. The present in vitro study aims to evaluate the influence of acetylene, argon, air, nitrogen and oxygen plasma on the shear bond strength between PEKK and one veneering composite. Firstly, to determine which bond test type should be applied, n = 40 PEKK specimens were treated with argon plasma. Both shear and tensile bond tests were performed and compared to the control group (n = 40). In shear bond testing, values were 8.14 ± 1.70 MPa for Argon plasma while 5.83 ± 1.42 MPa for control group. In tensile bond testing, Argon plasma 1.50 ± 0.51 MPa while control group 0.58 ± 0.50 MPa. Afterwards n = 160 PEKK specimens were treated with rocatec sandblasting (n = 20), adhesive (n = 20), acetylene (n = 20), argon (n = 20), air (n = 20), nitrogen (n = 20), oxygen (n = 20) plasma types and compared to the untreated control group (n = 20) using shear bond strength test (SBS). Additionally surface roughness and scanning electron microscopy analyses were performed. The following SBS values were revealed: 10.22 ± 1.06 MPa for rocatec; 9.89 ± 3.08 MPa for acetylene, 9.16 ± 1.48 MPa for adhesive, 7.54 ± 1.52 MPa for argon, 7.09 ± 1.99 MPa for air, 7.03 ± 1.48 MPa for nitrogen, 5.69 ± 1.59 MPa for oxygen plasma types and 4.71 ± 1.54 MPa for the control group. All groups, except control group, showed SBS over 5 MPa, which means that they are suitable for the clinical application, according to ISO 10477. Acetylene showed the highest SBS among all plasma types (p < 0.0001), which was on a level of rocatec sandblasting group. Rocatec and acetylene groups demonstrated Ra values significantly different to the reference group (p < 0.0001). Plasma treatment especially with acetylene gas can be an effective more convenient surface treatment method for strengthening the bond strength between PEKK and veneering composites than traditional sandblasting/adhesive treatment. • Influence of plasma with various feeding gases on the bond strenght between PEKK and veneering resin wasn't investigated yet. • Plasma treatment with acetylen may provid the shear bond strenght results comparable to the adhesive application. • Acetylene plasma provided the highest bond strength elevation among air, argon, oxygen and nitrogen feeding gases. [ABSTRACT FROM AUTHOR]

In this work, a series of four composites was developed by incorporation of two solid lubricants (SLs) (total amount 20 wt % and added in a complementary manner) viz. graphite (well known for thermal conductivity as well as good lubricity) and PTFE (Poly tetra fluoroethylene) (well known for excellent lubricity, but poor thermal conductivity) into PAEK (Poly aryl ether ketone) reinforced with short glass fibres. It was of interest to investigate how these two SLs work together, especially when with increasing contents of PTFE, thermal conductivity (TC) of the composites would decrease and lubricity should increase. The composites were characterized for density, TC and mechanical properties. Tribo-testing was done by varying load, velocity and against mild steel counterface. The composites showed very low wear rates (K 0 ≈ 10−16 m3/Nm) and ultra-low coefficient of friction (μ ≈ 0.03). With increase in PTFE contents, wear resistance and also TC decreased indicating TC was a dominating parameter to control the wear of composites. Worn surfaces were studied with scanning electron microscopy (SEM), energy dispersive X ray analysis (EDAX), Raman spectroscopy, XPS (X-ray photoelectron spectroscopy) and wettability analysis to understand the wear mechanisms. • Novel composites with very low μ ≈ 0.03 and K 0 - 1.3 × 10−16 m3/Nm were developed. • Graphite proved to be a better choice than selected grade of PTFE particles. • Thermal conductivity proved an edge over lubricity of particles. [ABSTRACT FROM AUTHOR]

A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the high conductivity associated with the pendant API group. The chemical structure of QPECH/PAEK-API membranes was identified by 1H nuclear magnetic resonace spectroscopy. A variety of membrane properties, such as anion conductivity, water uptake, length swelling percentage, and thermal, mechanical and chemical stability, were investigated. The QPECH/PAEK-API1 membrane showed quite high hydroxide ion conductivity, from 0.022 S cm−1 (30 °C) to 0.033 S cm−1 (80 °C), and excellent mechanical strength, associated with the low water uptake of less than 40%, even at 80 °C. Such high conductivity at relatively low water uptake is attributed to the concentrated cationic groups, in a cross-linked structure, facilitating feasible ion transport. Further, the QPECH/PAEK-API membranes showed thermal stability up to 250 °C, and chemical stability for 30 days in a 4 NaOH solution, without significant loss of ion exchange capacity. [ABSTRACT FROM AUTHOR]

The current work focusses on the designing and manufacturing process followed by tribo-evaluation of high-performance polymeric bearings based on tribo-optimized composition in earlier work on pin on disc configuration. A series of bearings was developed by a combination of graphite (10 wt%) as a primary lubricant and particles of metal chalcogenides (MoS 2 and WS 2) in micro and nano-form as secondary lubricants (10%) into Polyaryl ether ketone (PAEK) matrix (50%) reinforced by 30% glass fibers (GF). Tribo-performance assessment of bearings against shaft was critically done and performance of the product (bearing) and material (pin against disc) was critically compared to understand the difference in performance, from material to the product. • PAEK bearings were explored for first time. • Performance of bearings with materials were compared. • PV limit with very low μ and wear was reported. • Improvement in wear and μ due to NPs was observed compared to micro-particles. [ABSTRACT FROM AUTHOR]

Graphite is one of the most widely used solid lubricants in both, anti-friction and friction materials. The influence of particles in the composite mainly depends on its size, amount, its combination with fibers and other fillers etc. No efforts were done to optimize the amount of graphite to achieve very low friction and wear. A series of Polyaryl ether ketone (PAEK) composites with GF (short glass fibers) and increasing amount of graphite particles (10, 15, 20 and 25 wt %) were developed and characterized for various properties such as physical, mechanical, thermal along with adhesive wear performance in severe operating conditions (high pressure and velocity (PV)). Inclusion of graphite led to deterioration in strength and modulus but increase in thermal conductivity. The composites showed very low μ (friction coefficient) in the range of 0.04 and K 0 (specific wear rate) (∼2 × 10−16 m3/Nm). Composite with 15 wt % graphite proved to be significantly superior by showing highest PV limit value (154 MPa m/s) and very low μ (0.04) and K 0 (1.91 × 10−16 m3/Nm). The typical inferences were supported by various techniques such as Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), 3D profilometer, Raman spectroscopy on the worn surfaces. [ABSTRACT FROM AUTHOR]

Poly(aryl ether ketone)s (PAEKs) are promising materials for harsh environments, such as in high‐temperature steam applications. Here, the effect of high‐temperature steam on the crystallinity and mechanical properties of existing poly(ether ether ketone) (PEEK) and PEKK(T/I) polymers is investigated. Differential scanning calorimetry (DSC), wide‐angle X‐ray scattering or diffraction (WAXD), and dynamic mechanical analysis experiments show these materials undergo significant crystallization and reorganization after prolonged exposure to steam and suffer from embrittlement. In addition, we show that xanthydrol‐based crosslinks can provide the dimensional stability and stabilize the PEKK crystal structure. Mechanical tests demonstrate that the ductility is preserved for longer exposures to steam compared to neat PEKK, whereas DSC and WAXD data indicate xanthydrol crosslinks effectively stabilize the crystal structure against steam‐assisted crystallization. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47727. [ABSTRACT FROM AUTHOR]