Polyetheretherketone Composites Research Articles

Significantly enhanced wear resistance of PEEK by simply filling with modified graphitic carbon nitride

Graphitic carbon nitride (g-C3N4) was synthesized and the tribological behaviors of g-C3N4 reinforced poly-ether-ether-ketone (PEEK) were investigated. It was demonstrated that the addition of as-synthesized g-C3N4 (AS-CN) enhanced dramatically the wear resistance of PEEK, and meanwhile the friction coefficient was increased. Moreover, interlayer hydrogen bonds (H-bonds) of g-C3N4 played an important role in the tribological characteristics of PEEK composites. In comparison to AS-CN, thermal-etched g-C3N4 led to a lower friction coefficient owing to destruction of the H-bonds. On the contrary, hydroxylated g-C3N4 (h-CN) possessed strengthened interlayer H-bonds and a denser stacking structure, and hence further enhanced the wear resistance. Compared to carbon fibers, conventionally employed for developing anti-wear polymer composites, h-CN was identified to be significantly more effective for improving the wear resistance of PEEK, i.e. a very low specific wear rate of 4.0×10−7mm3/Nm was achieved by simply filling with 10vol% h-CN. Characterizations of tribofilms' nanostructures manifested that significant fraction of g-C3N4 transferred onto the counterface and led to generation of a load-carrying tribofilm. It is expected that the output of the present work will pave a route for developing binary and eco-friendly anti-wear materials.

Influence of processing conditions on tensile property of continuous glass fiber–reinforced PEEK composites fabricated by the co-wrapped yarn method

This study focused on the effect of processing conditions on the tensile properties of continuous glass fiber–reinforced polyether ether ketone composites, fabricated by co-wrapped yarn method, under different conditions. Their tensile properties were investigated in terms of thermal and fracture characterizations. The cooling rate significantly affected only the tensile modulus. However, both holding temperature and holding time had a significant effect on the tensile strengths and modulus. Although the effects of both were the same, the optimal increase of the holding time was found to be more beneficial.

Influences of surface treatments with abrasive paper and sand-blasting on surface morphology, hydrophilicity, mineralization and osteoblasts behaviors of n-CS/PK composite

The surfaces of nano-calcium silicate (n-CS)/polyetheretherketone (PK) composites were treated with abrasive paper and sand-blasting, and the surfaces performances of the as-treated composites were studied. The results showed that the surface roughness, hydrophilicity and mineralization of the simulated body fluid (SBF) of the composites surfaces were significantly improved, and the properties of the composites treated by with sand-blasting were better than those treated with abrasive paper. Moreover, the treated composites significantly promoted osteoblasts responses, such as cell attachment, spreading, proliferation and alkaline phosphatase (ALP) activity, compared to un-treated composites, and the cellular responses to the composites treated with sand-blasting were better than those treated with abrasive paper. The results suggested that surface treatment with sand-blasting was an effective method to greatly improve the surface bioperformances of the n-CS/PK composite, and this treated composite with improved bioactivity and cytocompatibility might be a promising implant material for orthopedic applications.

Influence of amorphous carbon layers on tribological properties of polyetheretherketone composite in contact with nitrided layer produced on Ti6Al4V titanium alloy

The key issue in bone implants biomechanics is – besides using biocompatible materials - the optimization of tribological properties of friction pairs occurring in joint implants e.g. knee and hip endoprothesis. Increasingly important role in these systems, alongside ceramics-on-ceramics and metal-on-metal, have metal-on-polymer friction pairs. Commonly used in orthopedics ultra-high molecular weight polyethylene (UHMWPE) does not meet the requirements of modern bone implants, mainly because of its harmful wear products which can cause inflammation and osteolysis of surrounding tissues after several years of using the endoprosthesis. Therefore, other polymer materials have been developed to replace UHMWPE, as well as several surface engineering methods are used for enhancing biocompatibility and tribological properties of applied materials. One of the materials to replace UHMWPE is increasingly used in medicine polyetheretherketone (PEEK) – a polymer material with a high biological indifference and mechanical properties.The article presents characteristics of TiN+Ti2N+αTi(N) nitrided layer produced on Ti6Al4V titanium alloy using glow discharge assisted nitriding process at the plasma potential, also known as the active screen plasma nitriding process and hydrogenated amorphous carbon doped with nitrogen layer a-C:N:H produced via RFCVD process on PEEK-based composite consisting of 10% graphite, 10% carbon fibers and 10% PTFE. Tribological properties of a-C:N:H – TiN+Ti2N+αTi(N) friction pair using “ball-on-disc” and “block-on-roll” tests were examined in correlation with microstructure (TEM, SEM, Raman spectroscopy) and surface morphology and topography (SEM, AFM, optical profilometer).The goal of this work is to present a new possibility of material solution for a ‘head-acetabulum’ friction pair in hip joint endoprosthesis using PEEK (PEEK T) as a replacement for commonly used UHMWPE and nitrided layer produced on Ti6Al4V titanium alloy using active screen plasma nitriding process.Amorphous carbon layer, 200nm thick, produced on PEEK composite significantly improved tribological properties of PEEK composite – TiN (nanocrystalline)+Ti2N+αTi(N) layer friction pair, decreasing the friction coefficient by 2 times and minimizing wear of both used materials in the point contact (“ball-on-disc” method) and in surface contact (“block-on-roll” method).

Functionalization of polyethetherketone for application in dentistry and orthopedics

AbstractSince late 1990s, polyetheretherketone (PEEK) has presented a promising polymeric alternative to metal implant components, particularly in orthopedic and traumatic applications. However, PEEK is biologically inert, which has constrained its potential applications. In this manner, enhancing the bioactivity of PEEK is a huge challenge that must be comprehended to completely understand the potential advantages. Up to now, two noteworthy methodologies are discussed to enhance the bioactivity of PEEK, including bulk and surface modification. Although the latter is extremely challenging due to the very high physical and chemical stability of the high performance polymer, there are some stated modification reactions in the literature, which will be collocated with in the literature-reported PEEK composites in the present article. We will furthermore add information on polymer-based drug delivery systems and the biofunctionalization of polymers in general and discuss their applicability for PEEK, as we estimate that these strategies will gain greater attention in the future. At the end of the article, our own research on the development of a PEEK-associated biodegradable drug-delivery system with potential application in dentistry or orthopedics will be highlighted.

Significant friction and wear reduction by assembling two individual PEEK composites with specific functionalities

In the present work, two polyetheretherketone (PEEK) composites, i.e. conventional composite filled with short carbon fibers (SCF) and nanocomposite filled with SiO2 nanoparticles, were mechanically assembled side-by-side using adhesive. The tribological behavior of the assembled sample was investigated using a Pin-On-Disc tribometer with the two composites' surfaces rubbing in succession along the same wear track on a steel counterpart. It was demonstrated that the assembled sample exhibited a greatly enhanced tribological performance in comparison to those obtained when the composites ran respectively. A synergetic role of the conventional composite and the nanocomposite was therefore identified. Moreover, it was manifested that the assembled sample showed a tribological performance comparable to the hybrid nanocomposite filled with combined SCF and SiO2 nanoparticles. The tribological mechanisms dominating the synergetic effect of the two composites were analyzed based on direct comparisons of tribofilm morphologies. It is expected that the present work provides a new design concept for tribo-enginnering components, i.e. assembling individual composites with specific functionalities.

Dynamic mechanical properties of carbon fibre-reinforced PEEK composites in simulated body-fluid

The work presents the fatigue mechanical properties of a composite material made of polyetheretherketone (PEEK) polymer and carbon fibres (CF) designed for structural biomaterials. Composite samples with various types of carbon fibre reinforcements were studied. The mechanical durability of the composite samples in simulated body solution was analysed. The samples were loaded for a predetermined number of cycles for various applied-force levels, at a frequency of 50Hz under a bending force, and at 1Hz under compression force. The mechanical changes were analysed taking into consideration the anisotropic structure of the composite samples made of fibre roving 1D, 2D tissue and carbon fibres in the form of braided fibre sleeves (MD). The ultrasonic method was applied to determine the changes in velocities measured in the composites. The average variations of mechanical stability of the composite samples kept in simulated body fluid were not significant after fatigue testing up to 1*106 cycles.

Effects of carbon fillers on the conductivity and tensile properties of polyetheretherketone composites

Polyetheretherketone (PEEK)‐based composites are used in aerospace applications due to their high mechanical strengths at temperatures >250°C, excellent chemical resistance properties, and outstanding dimensional stability. In this work, varying amounts of three different carbon fillers (carbon black [CB], graphene nanoplatelets [GNP], and carbon fiber [CF]) were added to PEEK to produce conductive composites for aerospace applications. Researchers extruded, injection molded, and performed electrical and thermal conductivity (TC) and tensile tests on GNP/PEEK, CB/PEEK, CF/PEEK, and CB/CF/PEEK composites. Five formulations could be used for electrostatic dissipative applications: 15 wt% GNP/PEEK, 20 wt% CF/PEEK, 2.5 wt% CB/10 wt% CF/PEEK, and 2.5 wt% CB/20 wt% CF/PEEK. Seven formulations could be used for electrically conductive applications: 30 wt% CF/PEEK, 5 wt% CB/PEEK, 7.5 wt% CB/PEEK, 10 wt% CB/PEEK, 2.5 wt% CB/30 wt% CF/PEEK, 5 wt% CB/30 wt% CF/PEEK, and 7.5 wt% CB/30 wt% CF/PEEK. The most conductive composite produced was 7.5 wt% CB/30 wt% CF/PEEK, which had an electrical resisitivity (1/electrical conductivity) of 0.56 Ω cm, a TC twice that of the neat PEEK, a tensile strength of 145 MPa, and a tensile modulus of 18.4 GPa. Per the authors' knowledge, properties on these GNP/PEEK, CB/PEEK, and CB/CF/PEEK composites have not been previously reported in the open literature. POLYM. COMPOS., 39:E807–E816, 2018. © 2016 Society of Plastics Engineers

Influence of femtosecond laser on the osteogenetic efficiency of polyetheretherketone and its composite

Objective: This study aimed to evaluate the effect of a femtosecond laser on the osteogenetic efficiency of polyetheretherketone (PEEK) and its composite for clinical applications. Methods: One hundred pieces of PEEK and its composite (6 × 4 × 2 mm3) were randomly divided into four groups and treated as follows: group A1, PEEK; group A2, PEEK + femtosecond laser; group B1, PEEK composite; and group B2, PEEK composite + femtosecond. The surface morphology of the pieces of each group was observed through scanning electron microscopy. The surface roughness and wettability, which were considered as the main parameters affecting cell adhesion characteristics of implants, were measured. The animals whose mandibles were implanted with the four groups of materials were killed at the end of 6 and 12 weeks. Various characterization tests, such as Cone Beam Computed Tomography (CBCT), push-out test, microscope test, and bone implant contact , were conducted to investigate the healing effect between materials and bones. Results: In group B1, the nanoparticles in PEEK were uniformly distributed. In groups A2 and B2, many periodic nanostructures were observed. The surface roughness and wettability of group B2 were significantly increased compared to those of the other groups ( p < 0.05). At each time point, the number of trabecular bones, contact strength, and BIC of group B2 were higher than those of the three other groups ( p < 0.05). Compared with those of group A1, the test results of group B1 were significantly improved. Conclusion: Femtosecond lasers can effectively enhance the biological activity of PEEK and its composite; PEEK composite exhibits better biological activity than PEEK.

Bioactive carbon–PEEK composites prepared by chemical surface treatment

Polyetheretherketone (PEEK) has attracted much attention as an artificial intervertebral spacer for spinal reconstruction. Furthermore, PEEK plastic reinforced with carbon fiber has twice the bending strength of pure PEEK. However, the PEEK-based materials do not show ability for direct bone bonding, i.e., bioactivity. Although several trials have been conducted for enabling PEEK with bioactivity, few studies have reported on bioactive surface modification of carbon–PEEK composites. In the present study, we attempted the preparation of bioactive carbon-PEEK composites by chemical treatments with H2SO4 and CaCl2. Bioactivity was evaluated by in vitro apatite formation in simulated body fluid (SBF). The apatite formation on the carbon–PEEK composite was compared with that of pure PEEK. Both pure PEEK and carbon-PEEK composite formed the apatite in SBF when they were treated with H2SO4 and CaCl2; the latter showed higher apatite-forming ability than the former. It is conjectured that many functional groups able to induce the apatite nucleation, such as sulfo and carboxyl groups, are incorporated into the dispersed carbon phase in the carbon–PEEK composites.

The Biologic Response to Polyetheretherketone (PEEK) Wear Particles in Total Joint Replacement: A Systematic Review.

BackgroundPolyetheretherketone (PEEK) and its composites are polymers resistant to fatigue strain, radiologically transparent, and have mechanical properties suitable for a range of orthopaedic applications. In bulk form, PEEK composites are generally accepted as biocompatible. In particulate form, however, the biologic response relevant to joint replacement devices remains unclear. The biologic response to wear particles affects the longevity of total joint arthroplasties. Particles in the phagocytozable size range of 0.1 µm to 10 µm are considered the most biologically reactive, particularly particles with a mean size of < 1 µm. This systematic review aimed to identify the current evidence for the biologic response to PEEK-based wear debris from total joint arthroplasties.Questions/purposes(1) What are the quantitative characteristics of PEEK-based wear particles produced by total joint arthroplasties? (2) Do PEEK wear particles cause an adverse biologic response when compared with UHMWPE or a similar negative control biomaterial? (3) Is the biologic response affected by particle characteristics?MethodsEmbase and Ovid Medline databases were searched for studies that quantified PEEK-based particle characteristics and/or investigated the biologic response to PEEK-based particles relevant to total joint arthroplasties. The keyword search included brands of PEEK (eg, MITCH, MOTIS) or variations of PEEK types and nomenclature (eg, PAEK, CFR-PEEK) in combination with types of joint (eg, hip, knee) and synonyms for wear debris or immunologic response (eg, particles, cytotoxicity). Peer-reviewed studies, published in English, investigating total joint arthroplasty devices and cytotoxic effects of PEEK particulates were included. Studies investigating devices without articulating bearings (eg, spinal instrumentation devices) and bulk material or contact cytotoxicity were excluded. Of 129 studies, 15 were selected for analysis and interpretation. No studies were found that isolated and characterized PEEK wear particles from retrieved periprosthetic human tissue samples.ResultsIn the four studies that quantified PEEK-based particles produced using hip, knee, and spinal joint replacement simulators, the mean particle size was 0.23 µm to 2.0 µm. The absolute range reported was approximately 0.01 µm to 50 µm. Rod-like carbon particulates and granular-shaped PEEK particles were identified in human tissue by histologic analysis. Ten studies, including six animal models (rat, mouse, and rabbit), three cell line experiments, and two human tissue retreival studies, investigated the biologic response to PEEK-based particles. Qualitative histologic assessments showed immunologic cell infiltration to be similar for PEEK particles when compared with UHMWPE particles in all six of the animal studies identified. However, increased inflammatory cytokine release (such as tumor necrosis factor-α) was identified in only one in vitro study, but without substantial suppression in macrophage viability. Only one study tested the effects of particle size on cytotoxicity and found the largest unfilled PEEK particles (approximately 13 µm) to have a toxic effect; UHMWPE particles in the same size range showed a similar cytotoxic effect.ConclusionsWear particles produced by PEEK-based bearings were, in almost all cases, in the phagocytozable size range (0.1–10 µm). The studies that evaluated the biologic response to PEEK-based particles generally found cytotoxicity to be within acceptable limits relative to the UHMWPE control, but inconsistent when inflammatory cytokine release was considered.Clinical RelevanceTo translate new and advanced materials into clinical use more quickly, the clinical relevance and validity of preclinical tests need to be improved. To achieve this for PEEK-based devices, human tissue retrieval studies including subsequent particle isolation and characterization analyses are required. In vitro cell studies using isolated wear particles from tissue or validated joint replacement simulators, instead of manufactured particles, are also required.

Influence of surface activated carbon nano fiber on thermo-mechanical properties of high performance polymeric nano composites

This investigation highlights the influence of plasma modified carbon nano fiber (CNF) on the various properties of poly ether ketone (PEK). CNFs were modified with oxygen plasma under low pressure to enhance the interfacial adhesion between the reinforcement and matrix. Significant changes are evident in the elemental composition of oxygen and carbon on the plasma modified CNFs as observed by X-ray photo electron spectroscopy. Based on results from compression and tensile strength, significant change in the mechanical properties of the composites is observed. Dynamic mechanical thermal analysis (DMTA) reveals that the storage modulus increases on reinforcing modified CNF in PEK. The increase in modulus is noticeable only up to 1.5% wt reinforcement of CNF, while higher percentage of reinforcement leads to decline in properties. DMTA studies also clearly shows that the dispersion of CNF is not uniform after 1.5% of CNF reinforcement. However, differential scanning calorimeter and thermo gravimetric analysis studies reveal that the thermal properties of the CNF reinforced composite do not vary significantly. Thermal conductivity results show a substantial increase in the thermal conductivity of polymeric composites on increasing the reinforcements. Transmission electron microscopy (TEM) analysis reveals that there is uniform dispersion of CNF in PEK. TEM also clearly shows that higher percentage of CNF leads to agglomeration. Physico-chemical analysis indicates that the contact angle increases on increasing the reinforcements. These findings would be highly useful to make way for PEK composites for high temperature and high strength application.

Effect of the type, size and concentration of solid lubricants on the tribological properties of the polymer PEEK

Poly-ether-ether-ketone (PEEK) is a high-performance, temperature-resistance polymer that is finding an increasing range of applications. In order to even enhance PEEK׳s mechanical and tribological properties particles of different compositions, shapes and sizes are added into its matrix. PEEK has already been combined with many different particles; however, very rarely MoS2 and WS2 – two state-of-the-art solid-lubricants – were added into the PEEK matrix. Furthermore, a comprehensive tribological study combining MoS2 and WS2 particles of different sizes and concentrations has not yet been reported. In this investigation we looked at the effect of micro- and nanosized MoS2 and WS2 particles in PEEK on the dry-sliding tribological behaviour against stainless steel (100Cr6). A non-conventional technique, i.e., the sintering of dry-pressed compacts, was used to prepare the PEEK composites. The results show that all the particles, irrespective of their composition and size, reduce the friction (up to 30%); however, the nanoscale particles require a higher concentration to form an effective low-friction tribofilm. The formation of a tribofilm is necessary to reduce the wear of all the composites (up to 51%); this is strongly promoted by the addition of nano- or microparticles of both the MoS2 and WS2 materials. In addition, the hardness, which is greatly increased by the addition of all the particles, significantly improves the wear behaviour. The results of XPS analyses showed that the oxidation occurs during tribological sliding, which reduces particles beneficial wear behaviour effects.

Polyetheretherketone (PEEK) for medical applications.

Polyetheretherketone (PEEK) is a polyaromatic semi-crystalline thermoplastic polymer with mechanical properties favorable for bio-medical applications. Polyetheretherketone forms: PEEK-LT1, PEEK-LT2, and PEEK-LT3 have already been applied in different surgical fields: spine surgery, orthopedic surgery, maxillo-facial surgery etc. Synthesis of PEEK composites broadens the physicochemical and mechanical properties of PEEK materials. To improve their osteoinductive and antimicrobial capabilities, different types of functionalization of PEEK surfaces and changes in PEEK structure were proposed. PEEK based materials are becoming an important group of biomaterials used for bone and cartilage replacement as well as in a large number of diverse medical fields. The current paper describes the structural changes and the surface functionalization of PEEK materials and their most common biomedical applications. The possibility to use these materials in 3D printing process could increase the scientific interest and their future development as well.

Characterization of New PEEK/HA Composites with 3D HA Network Fabricated by Extrusion Freeforming.

Addition of bioactive materials such as calcium phosphates or Bioglass, and incorporation of porosity into polyetheretherketone (PEEK) has been identified as an effective approach to improve bone-implant interfaces and osseointegration of PEEK-based devices. In this paper, a novel production technique based on the extrusion freeforming method is proposed that yields a bioactive PEEK/hydroxyapatite (PEEK/HA) composite with a unique configuration in which the bioactive phase (i.e., HA) distribution is computer-controlled within a PEEK matrix. The 100% interconnectivity of the HA network in the biocomposite confers an advantage over alternative forms of other microstructural configurations. Moreover, the technique can be employed to produce porous PEEK structures with controlled pore size and distribution, facilitating greater cellular infiltration and biological integration of PEEK composites within patient tissue. The results of unconfined, uniaxial compressive tests on these new PEEK/HA biocomposites with 40% HA under both static and cyclic mode were promising, showing the composites possess yield and compressive strength within the range of human cortical bone suitable for load bearing applications. In addition, preliminary evidence supporting initial biological safety of the new technique developed is demonstrated in this paper. Sufficient cell attachment, sustained viability in contact with the sample over a seven-day period, evidence of cell bridging and matrix deposition all confirmed excellent biocompatibility.

Response of Human Osteoblast to n-HA/PEEK--Quantitative Proteomic Study of Bio-effects of Nano-Hydroxyapatite Composite.

Nano-sized hydroxyapatite (n-HA) is considered as a bio-active material, which is often mixed into bone implant material, polyetheretherketone (PEEK). To reveal the global protein expression modulations of osteoblast in response to direct contact with the PEEK composite containing high level (40%) nano-sized hydroxyapatite (n-HA/PEEK) and explain its comprehensive bio-effects, quantitative proteomic analysis was conducted on human osteoblast-like cells MG-63 cultured on n-HA/PEEK in comparison with pure PEEK. Results from quantitative proteomic analysis showed that the most enriched categories in the up-regulated proteins were related to calcium ion processes and associated functions while the most enriched categories in the down-regulated proteins were related to RNA process. This enhanced our understanding to the molecular mechanism of the promotion of the cell adhesion and differentiation with the inhibition of the cell proliferation on n-HA/PEEK composite. It also exhibited that although the calcium ion level of incubate environment hadn’t increased, merely the calcium fixed on the surface of material had influence to intracellular calcium related processes, which was also reflect by the higher intracellular Ca2+ concentration of n-HA/PEEK. This study could lead to more comprehensive cognition to the versatile biocompatibility of composite materials. It further proves that proteomics is useful in new bio-effect discovery.

Feasibility of polyetherketone (PEK) composites: a solution for long-term nuclear waste storage

This investigation highlights the effect of radiation, chemical and thermal environments on mechanical and thermal properties of polyetherketone (PEK) composites and its rationale for long-term nuclear waste storage. The tests are conducted on samples manufactured using PEK and PEK reinforced with modified carbon nano fibre (CNF). The specimens are subjected to gamma radiation doses of 5 MGy, which is equivalent to the cumulative dosage of radiation from spent nuclear fuel until the radioactivity neutralises completely. Studies under transmission electron microscopy (TEM) reveal that there is a uniform dispersion of modified CNF in PEK. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) indicate that there are no significant changes in thermal properties of PEK and PEK composite when exposed to aggressive environments. It is observed that tensile strength of polymeric samples remains unchanged when exposed to gamma radiation and thermo-chemical environment.

Research on Progress of Tribological Modification of Polyetheretherketone

The characteristics and application of poly ether ether ketone (PEEK) has been reviewed in the paper. The tribological modification of PEEK composites which were reinforced by inorganic fillers, the fiber, polymer blends, plasma and mixed modification were introduced. Finally research progress of tribological modification of PEEK composites was forecasted.

Preparation of polyetheretherketone composites with nanohydroxyapatite rods and carbon nanofibers having high strength, good biocompatibility and excellent thermal stability

The WST-1 assay shows that the PEEK/15 vol% nHA–1.9 vol% CNF hybrid composite has excellent biocompatibility.

Investigation on polyetheretherketone composite for long term storage of nuclear waste

This investigation highlights the effect of radiation, chemical and thermal environments on mechanical and thermal properties of Polyetheretherketone (PEEK) composites, which could prove to be an alternative material for long term storage of nuclear wastes. The tests are conducted on specimens made from PEEK and PEEK reinforced with carbon short fiber. The specimens are subjected to radiation doses, equivalent to the cumulative dosage for 500 years followed by exposure under highly corrosive and thermal environments. Studies under optical microscopy reveal that the dispersion of carbon short fiber in the PEEK Composites is significantly uniform. Differential scanning calorimeter (DSC) and thermo gravimetric analysis (TGA) indicates that there are no significant changes in thermal properties of PEEK composite when exposed to aggressive environments. It is further observed that there are no significant changes in mechanical properties of the composite after exposure to radiation and thermo-chemical environment.