Poly-ether-ether-ketone Coatings Research Articles

Electrophoretic deposition of polyetheretherketone/polytetrafluoroethylene on 316L SS with improved tribological and corrosion properties for biomedical applications

Introduction316L stainless steel (316L SS) has poor wear and corrosion resistance compared to that of the Cp-Ti and Ti-6Al-4V implants [when studied under a physiological environment using phosphate-buffered saline (PBS)]. However, 316L SS implants are cost-effective. Their wear and corrosion properties can be improved by depositing biocompatible coatings.MethodIn this research work, a polymer coating of polyetheretherketone (PEEK) and polytetrafluoroethylene (PTFE) was deposited at optimized parameters (20 V for 3 min) on 316L SS via electrophoretic deposition (EPD). We compared the performance between of the PEEK coating and hybrid PEEK/PTFE coatings for biomedical applications. The PEEK/PTFE coating was sintered at 350°C for 30 min.Results and DiscussionScanning electron microscopy (SEM) analysis revealed that the PEEK/PTFE coating showed a uniform coating with a uniform thickness of ∼80 µm. Fourier transform infrared (FTIR) spectroscopy analysis confirmed the presence of bonds attributed to the PEEK and PTFE coatings. The PEEK/PTFE coating exhibited adequate average surface roughness (Ra) of 2.1 ± 0.2 µm with a high value of contact angle of 132.71 ± 3, indicating the hydrophobic nature of the PEEK/PTFE coating. Scratch tests evaluated that the PEEK/PTFE coating demonstrated a 7 N load, which indicated the good adhesion between the coating and 316L SS. Furthermore, the PEEK/PTFE coating demonstrated good wear resistance, capable of withstanding a 7 N load under dry conditions, and showed a specific wear rate of ∼0.0114 mm3/Nm. Electrochemical analysis conducted using the phosphate-buffered saline (PBS) solution demonstrated that the corrosion rate of 316L SS was reduced from 0.9431 mpy to 0.0147 mpy by depositing the PEEK/PTFE coating. Thus, the developed coatings present suitable wear and corrosion resistance and are thus considered for potential orthopedic applications.

Wear-Resistant Low-friction Atmospheric Pressure Plasma Spray Coatings for Sustainable (Bio-based Recyclable) Materials

Coatings from polyetheretherketone (PEEK), polyamide 12 (PA12), molybdenumdisulfide (MoS2), zinc (Zn), and graphite (C) powder mixtures were deposited on PA6, PA12, and PEEK substrates by an atmospheric pressure plasma (APP) spray jet system. Several tenth of µm thick coatings on PA6 and PA12 substrates result in an almost halved surface roughness Ra ~8 µm, Rq ~10 µm and Rz ~60 µm, whereas a significant increase of all surface roughness parameters is observed for PEEK substrates (Ra < 1 µm → 4 µm, Rq < 1 µm → 5 µm, Rz < 5 µm → 20 µm). The surface roughness, powder composition, and selected APP process parameter strongly influence the coefficient of friction (COF) and specific wear rate ki of the APP coatings in rotational ball-on-disc tribological testing. The COF of PA12/MoS2/C coatings on PA6 substrates manufactured by selective laser sintering (SLS) is ~0.2 after 628 m sliding distance, resulting in a very low calculated ki of 6.3 × 10−7 mm3/Nm. A similarly low COF and ki was observed for PEEK coatings deposited at a current of 75 A and 60 mm jet–substrate distance on SLS PA12 substrate. Although the COF of Zn/C/MoS2 coatings on PEEK drops down below 0.1 after 1884 m sliding distance under nitrogen atmosphere the corresponding ki of 5.6 × 10−5 mm3/Nm is higher. Still all calculated specific wear rates are significantly lower than the reported values of polyamide-polytetrafluorethylene (PTFE)-polyethylene composites (1.9–8.0 × 10−2 mm3/Nm) and partly even outperform PEEK-PTFE composites (1.0 × 10−7–2.5 × 10−6), currently applied in demanding wear regimes.

Corrosion, surface, and tribological behavior of electrophoretically deposited polyether ether ketone coatings on 316L stainless steel for orthopedic applications

Electrophoretic deposition (EPD) of polyether ether ketone (PEEK) coatings on metallic implants has recently attracted a great deal of interest; however, further investigation into their corrosion, surface, and tribological properties is required for their clinical application. Using Potentiodynamic polarization and Mott-Schottky analysis of PEEK coatings, we analyzed the electrochemical corrosion behavior of electrophoretically deposited PEEK coatings on 316L stainless steel (SS) substrates. In addition, the tribological behavior of the coatings was determined through pin-on-disc and scratch testing. Initially, the EPD parameters were optimized using a Taguchi Design of Experiment (DoE) approach. The coatings exhibited irregular shaped grains along with ∼66 μm of thickness. Fourier transform infrared spectroscopy confirmed the presence of functional groups ascribed with PEEK. The coatings were moderately hydrophobic and had an average roughness of ∼2 μm. The corrosion studies demonstrated promising features of current density and corrosion potential, indicating that corrosion resistance significantly improves with PEEK coating. Electrochemical impedance spectroscopy also confirmed the corrosion resistance of PEEK coating. The coatings exhibited a slightly lower wear resistance than SS samples, but still possessed adequate wear and scratch resistance for biomedical applications. The current study confirmed that the PEEK coatings on metallic implants is effective for orthopedic applications where corrosion and tribology are major concerns.

Tribological and mechanical behavior of tantalum and its compounds reinforced PEEK coatings for TKR

In biomedical applications, poly-ether-ether-ketone (PEEK) is capable of modifying traditional metal components, but still lacks strength and wear resistance. In this study, a series of soft-hard phase structure coatings with modified PEEK are produced by combining PEEK as the soft-antifriction phase, as well as tantalum (Ta), tantalum carbide (TaC), and tantalum nitride (TaN) nanoparticles as the hard-wear resistance phase. The coatings of a total knee replacement system were evaluated by finite element analysis (FEA). As a result, the reinforcement of nanoparticles has a significant impact on stress distribution and transfer, improving mechanical behavior and wear resistance, whereas TaC nanoparticles have the greatest ability to enhance these properties. The implant with the modified coating (PEEK/TaC) can be expected to reduce the stress of the Ti implant substrate by about 38.3 % compared to unmodified PEEK coating. Combined the experimental and simulated results showed that the modified coatings have the potential to enhance the lifespan of TKR Ti-based implants.

Tantalum nanoparticles reinforced polyetheretherketone coatings on titanium substrates: Bio-tribological and cell behaviour

As a biomaterial for bone repair, the application of polyetheretherketone (PEEK) has been limited by its poor wear resistance and cell behaviour. Inspired by the double ‘soft-hard’ phase structure, tantalum (Ta)/PEEK composite coating was fabricated on a titanium surface. All composite coatings had a lower friction coefficient and wear resistance under fetal bovine serum conditions. The adhesion, proliferation, and osteogenic differentiation of rat bone osteoblastic cells (MC3T3-E1) and mononuclear macrophage cells (RAW264.7) on the Ta/PEEK composite coating was enhanced. In particular, composite coatings effectively reduced inflammatory markers, with cytokines TGF-β and IL-10 released. As a result, titanium alloys with Ta reinforced PEEK coatings could exhibit improved bioactivity and tribology.

Abrasive wear of PEEK and ATSP-based polymer composite coatings under lunar regolith conditions

Abrasive wear of polyether ether ketone (PEEK) and aromatic thermosetting co-polyester (ATSP) based polymer composite coatings were examined with lunar regolith simulant environment by conducting pin-on-disk experiments under dry sliding conditions, contact pressure of 17.5 MPa, and sliding speed of 0.25 m/s. Three different tribo-interfaces, namely metal-on-metal, metal-on-polymer, and polymer-on-polymer were designed to evaluate the efficacy of each polymer coating on the friction and wear improvement, as well as the extent of sand-dust mitigation at the interface. The polymer-on-polymer system resulted in significant reduction in friction up to 70%. The wear mechanism was a mixed mode of two-body and three-body abrasion for metal-on-metal and metal-on-polymer tribopairs, while the polymer-on-polymer tribopair significantly mitigated the sand and dust accumulation at the interface with three-body abrasion as the dominant wear. Both polymer composites showed similar frictional behavior, while ATSP composite showed superior abrasive wear resistance, particularly under small size dust (<38 μm size) environment.

Performance of a Direct Bonded Sub-Millimeter Peek Coating for Hydrodynamic Plain Bearings

Abstract Despite their superior tribological properties, thick-layer bearing coatings based on polyetheretherketone (PEEK) have up to now not been applied in a very high number of plain bearings for industrial applications. This can at least partly be credited to the high costs and low flexibility associated with the coating process for these materials. At the same time, while thick-layer polytetrafluoroethylene (PTFE) coatings have been successfully applied in industrial plain bearings for around 50 years, thin-layer PTFE coatings today constitute the majority of applications of PTFE in plain bearings. It is therefore reasonable to assume a similar approach for thin-layer PEEK coatings. This article reports the performance of a thin-layer PEEK coating directly applied on a mild steel substrate, with results ranging from first sample test through component tests to application in an actual machine and behavior during realistic operating conditions and induced bearing failure.

Strategies to Reduce Biofilm Formation in PEEK Materials Applied to Implant Dentistry-A Comprehensive Review.

Polyether-ether-ketone (PEEK) has emerged in Implant Dentistry with a series of short-time applications and as a promising material to substitute definitive dental implants. Several strategies have been investigated to diminish biofilm formation on the PEEK surface aiming to decrease the possibility of related infections. Therefore, a comprehensive review was carried out in order to compare PEEK with materials widely used nowadays in Implant Dentistry, such as titanium and zirconia, placing emphasis on studies investigating its ability to grant or prevent biofilm formation. Most studies failed to reveal significant antimicrobial activity in pure PEEK, while several studies described new strategies to reduce biofilm formation and bacterial colonization on this material. Those include the PEEK sulfonation process, incorporation of therapeutic and bioactive agents in PEEK matrix or on PEEK surface, PEEK coatings and incorporation of reinforcement agents, in order to produce nanocomposites or blends. The two most analyzed surface properties were contact angle and roughness, while the most studied bacteria were Escherichia coli and Staphylococcus aureus. Despite PEEK’s susceptibility to biofilm formation, a great number of strategies discussed in this study were able to improve its antibiofilm and antimicrobial properties.

MECHANICAL AND TRIBOLOGICAL ANALYSIS OF MONOLITH AND COATING POLYETHERETHERKETONE

In this work, a comparative analysis of the micromechanical and tribological properties of polyetheretherketone (PEEK) in bulk and coating form was performed. The PEEK 708 coating was applied on a Ti6Al4V titanium alloy flat specimen using the electrophoretic deposition method. The micromechanical properties were determined through indentation tests performed using the Vickers method and scratch tests. Based on research work, the Vickers hardness (HV), elastic modulus (E), scratch hardness (HS), and Micro Mar Resistance (MMR) were determined. The tribological properties were defined by the coefficient of friction (fs and fw), which was obtained in scratch tests and ball-on-disk tests. The results of this research indicate, despite the slightly higher Vickers hardness (HV) of the PEEK 708 coating (HV=350 MPa, HS=300 MPa) relative to PEEK bulk (HV=300 MPa, HS=210 MPa), that there is an almost 40% difference between the scratch hardness (HS) values of these PEEK forms. It appears from the result analysis in this paper that testing methods to determine the micromechanical and tribological properties of PEEK in monolith form can be used for both PEEK coatings. Under certain test conditions, the impact of the substrate properties on the results of the PEEK 708 coating was not found.

Porous PEEK improves the bone-implant interface compared to plasma-sprayed titanium coating on PEEK

Polyether-ether-ketone (PEEK) is one of the most common materials used for load-bearing orthopaedic devices due to its radiolucency and favorable mechanical properties. However, current smooth-surfaced PEEK implants can lead to fibrous encapsulation and poor osseointegration. This study compared the in vitro and in vivo bone response to two smooth PEEK alternatives: porous PEEK and plasma-sprayed titanium coatings on PEEK. MC3T3 cells were grown on smooth PEEK, porous PEEK, and Ti-coated PEEK for 14 days and assayed for calcium content, osteocalcin, VEGF and ALP activity. Osseointegration was investigated by implanting cylindrical implants into the proximal tibiae of male Sprague Dawley rats for 8 weeks. Bone-implant interfaces were evaluated using μCT, histology and pullout testing. Cells on porous PEEK surfaces produced more calcium, osteocalcin, and VEGF than smooth PEEK and Ti-coated PEEK groups. Bone ingrowth into porous PEEK surfaces was comparable to previously reported porous materials and correlated well between μCT and histology analysis. Porous PEEK implants exhibited greater pullout force, stiffness and energy-to-failure compared to smooth PEEK and Ti-coated PEEK, despite Ti-coated PEEK exhibiting a high degree of bone-implant contact. These results are attributed to increased mechanical interlocking of bone with the porous PEEK implant surface. Overall, porous PEEK was associated with improved osteogenic differentiation in vitro and greater implant fixation in vivo compared to smooth PEEK and Ti-coated PEEK. These results suggest that not all PEEK implants inherently generate a fibrous response and that topography has a central role in determining implant osseointegration.

Polymer coatings based on sulfonated-poly-ether-ether-ketone films for implant dentistry applications

Poly-ether-ether-ketone (PEEK) is one of the most important biocompatible polymers and its sulfonation has been studied for biomedical applications. The aim of the present study is to produce, to characterize and to assess bioactivity of PEEK coatings with sulfonated PEEK (SPEEK) films. Biomedical grade PEEK (Invibio®, Batch: D0602, grade: NI1) was functionalized using sulfuric acid 98%. SPEEK was dissolved into DMSO or into DMF, both at 10% mass/volume. PEEK bars (N = 18) and cylinders (N = 27) were manufactured by compression molding and heating. SPEEK/DMSO and SPEEK/DMF were drop casted at PEEK bars and dip coated at PEEK cylinders (PEEK + SPEEK/DMSO and PEEK + SPEEK/DMF). Characterization was performed through Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and contact angle measurements. Bioactivity was assessed by immersion of samples at SBF for 1, 7 and 21 days, followed by SEM, energy-dispersive analysis (EDX) and FTIR analysis. Statistical analysis was carried out by one-way analysis of variance (ANOVA) (p = 0.05). Characteristic bands of PEEK and SPEEK, were identified through FTIR spectrum analysis, while semicrystallinity was confirmed by XRD. PEEK + SPEEK/DMF showed more evident physicochemical modifications. PEEK + SPEEK/DMSO provided a more regular and hydrophobic surface, observed through SEM and contact angle measurements. SEM/EDX showed that precipitates of calcium were formed at PEEK + SPEEK/DMSO and PEEK + SPEEK/DMF at all experimental times, but materials were not considered bioactive. Interesting surface properties were achieved with SPEEK coatings but the production of SPEEK films at PEEK surface has to be further improved and biologically tested. Schematic diagram showing the methodology applied in this study to prepare PEEK and SPEEK samples, as well as the promising application of the material.

Blood Compatibility of ZrO₂ Particle Reinforced PEEK Coatings on Ti6Al4V Substrates.

Titanium (Ti) and its alloys are widely used in biomedical devices. As biomaterials, the blood compatibility of Ti and its alloys is important and needs to be further improved to provide better functionality. In this work, we studied the suitability of zirconia (ZrO2) particle reinforced poly-ether-ether-ketone (PEEK) coatings on Ti6Al4V substrates for blood-contacting implants. The wettability, surface roughness and elastic modulus of the coatings were examined. Blood compatibility tests were conducted by erythrocytes observation, hemolysis assay and clotting time of recalcified human plasma, to find out correlations between the microstructure of the ZrO2-filled PEEK composite coatings and their blood compatibilities. The results suggested that adding ZrO2 nanoparticles increased the surface roughness and improved the wettability and Derjaguin-Muller-Toporov (DMT) elastic modulus of PEEK coating. The PEEK composite matrix coated Ti6Al4V specimens did not cause any aggregation of erythrocytes, showing morphological normal shapes. The hemolysis rate (HR) values of the tested specimens were much less than 5% according to ISO 10993-4 standard. The values of plasma recalcification time (PRT) of the tested specimens varied with the increasing amount of ZrO2 nanoparticles. Based on the results obtained, 10 wt % ZrO2 particle reinforced PEEK coating has demonstrated an optimum blood compatibility, and can be considered as a candidate to improve the performance of existing PEEK based coatings on titanium substrates.

Functionalized, biocompatible, and impermeable nanoscale coatings for PEEK

Biologically compatible coatings that provide hermetic seal could resolve a major technological hurdle in the attempt to replace metals with polymers for biochips and active medical implants. The use of amorphous carbon/diamond like carbon (a-C:H) coatings to hermetically seal and biologically enhance polyether-ether-ketone (PEEK) for biomedical device integration in the human body was investigated. The PEEK coating functionality (sp3/sp2 ratio), hardness and thickness (70–200nm) were controlled, by varying H2 and N2 concentration during the plasma operation with CH4. a-C:H coatings having the highest indentation modulus of 13.5GPa, originate out of a CH4 (90%) rich composition. Even in a mixture of 70/30 H2/CH4 the hardness is 4.76GPa, corresponding to hard and dense coatings. In all tested conditions of deposition coatings hardens was sufficient for the purpose of PEEK implants modification. The synthesized (a-C:H) nanoscale coatings were not water permeable as measured by the hydrolysis test, resolving the traditional challenge of swelling in wet environment. The hardness of the coatings showed strong correlations with the thickness, surprisingly however, with no correlations with the sp3/sp2 ratio. Selected non water permeable nanoscale coating on PEEK showed strong bioactivity by being viable for human osteoblast (hFOB) and human fibroblast (hGF) cells without toxicity issues. No correlation was observed between the coatings sp3/sp2 ratio and biological performance.

PEEK (polyether-ether-ketone)-coated nitinol wire: Film stability for biocompatibility applications

High quality biocompatible poly-ether-ether-ketone (PEEK) coatings were produced on NiTi shape memory alloy wires using dipping deposition from colloidal aqueous PEEK dispersions after substrate surface treatment. The surface morphology and microstructure were investigated by Scanning Electron Microscopy at every step of the process from the as-received Nitinol substrate to the ultimate PEEK-coated NiTi wire. Nanoscratch tests were carried out to access the adhesive behavior of the polymer coated film to the NiTi. The results indicate that the optimum process conditions in cleaning, chemical etching, and electropolishing the NiTi, were the most important and determining parameters to be achieved. Thus, high quality PEEK coatings were obtained on NiTi wires, straight or curved (even with a U-shape) with a homogeneous microstructure along the wire length and a uniform thickness of 12μm without any development of cracks or the presence of large voids. The biocompatibility of the PEEK coating film was checked in fibrobast cultured cells. The coating remains stable in biological environment with negligible Ni ion release, no cytotoxicity, and no delamination observed with time.

Influence of polyetheretherketone coatings on the Ti–13Nb–13Zr titanium alloy's bio-tribological properties and corrosion resistance

Polyetheretherketone (PEEK) coatings of 70–90μm thick were electrophoretically deposited from a suspension of PEEK powder in ethanol on near-β Ti–13Nb–13Zr titanium alloy. In order to produce good quality coatings, the composition of the suspension (pH) and optimized deposition parameters (applied voltage and time) were experimentally selected. The as-deposited coatings exhibited the uniform distribution of PEEK powders on the substrate. The subsequent annealing at a temperature above the PEEK melting point enabled homogeneous, semi-crystalline coatings with spherulitic morphology to be produced. A micro-scratch test showed that the coatings exhibited very good adhesion to the titanium alloy substrate. Coating delamination was not observed even up to a maximal load of 30N. The PEEK coatings significantly improved the tribological properties of the Ti–13Nb–13Zr alloy. The coefficient of friction was reduced from 0.55 for an uncoated alloy to 0.40 and 0.12 for a coated alloy in a dry sliding and sliding in Ringer's solution, respectively. The PEEK coatings exhibited excellent wear resistance in both contact conditions. Their wear rate was more than 200 times smaller compared with the wear rate of the uncoated Ti–13Nb–13Zr alloy. The obtained results indicate that electrophoretically deposited PEEK coatings on the near-β titanium alloy exhibit very useful properties for their prospective tribological applications in medicine.

Influence of PEEK Coating on Hip Implant Stress Shielding: A Finite Element Analysis.

Stress shielding is a well-known failure factor in hip implants. This work proposes a design concept for hip implants, using a combination of metallic stem with a polymer coating (polyether ether ketone (PEEK)). The proposed design concept is simulated using titanium alloy stems and PEEK coatings with thicknesses varying from 100 to 400 μm. The Finite Element analysis of the cancellous bone surrounding the implant shows promising results. The effective von Mises stress increases between 81 and 92% for the complete volume of cancellous bone. When focusing on the proximal zone of the implant, the increased stress transmission to the cancellous bone reaches between 47 and 60%. This increment in load transferred to the bone can influence mineral bone loss due to stress shielding, minimizing such effect, and thus prolonging implant lifespan.

Electrophoretic Deposition of Polyetheretherketone Composites, Containing Huntite and Alumina Platelets

Cationic and anionic polyelectrolytes were investigated for the application as charging agents for the electrophoretic deposition (EPD) of polyetheretherketone (PEEK) and composite coatings, containing huntite or alumina platelets. The use of cationic chitosan (CT) allowed for the fabrication of PEEK coatings by cathodic EPD. Anodic PEEK coatings were prepared using sodium alginate (AL) and poly[1-[4-(3-carboxy-4-hydroxyphenylazo)benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). The EPD of huntite and PEEK-huntite composites was achieved using AL and PAZO. The EPD of alumina and PEEK-alumina coatings was performed using PAZO. The comparison of the experimental results and molecular structures of AL and PAZO provided an insight into the influence of salicylate ligands of PAZO on adsorption of this polyelectrolyte on inorganic surfaces. The unique physical properties of PAZO, coupled with strong adsorption of this material on organic and inorganic surfaces, pave the way for the fabrication of functional composites by EPD. The deposition mechanism, deposition kinetics and deposit microstructure were investigated. Huntite is advanced flame retardant material with relatively high decomposition temperature, which is of special interest for the incorporation in polymers, such as PEEK, which require thermal processing. It was found that PEEK composites, containing flame retardant huntite additives, can be prepared by EPD. The composite coatings provided corrosion protection of steel.

Electrophoretically Deposited Polymeric Films: Evidence of Correlation between Electrochemical Impedance Spectroscopy Measurements and Morphological Properties

Electrochemical Impedance Spectroscopy (EIS) was used in order to investigate coatings obtained by Electrophoretic Deposition (EPD) from a morphological point of view. The analyzed samples were made of polyetheretherketone (PEEK), also mixed with alumina or polytetrafluoroethylene (PTFE), and were characterized by different thickness, porosity and roughness. For each kind of samples, a suitable equivalent circuit was used to interpolate EIS spectra. A linear correlation between thickness and Rcoat of PEEK coatings was found, whereas an exponential correlation between Cdl and thickness and porosity was observed for PEEK-Alumina composite coatings. Moreover, when the coating roughness was the most relevant feature, a Warburg element (with an impedance equal to ZCPE = A/(jω)n) was inserted in the equivalent circuit. In this case, the roughness was inversely correlated with n. These results indicate that electrochemical impedance spectroscopy can be used as a non-destructive technique to evaluate, at least qualitatively, the main morphological characteristics of EPD coatings.

Characterization of polyetheretherketone particle suspensions for electrophoretic deposition

ABSTRACTSuspensions of polyetheretherketone (PEEK) using mixture of ethanol and isopropanol as solvent were prepared to carry out PEEK electrophoretic deposition (EPD). The rheological behavior and suspension structure of PEEK particles dispersed in co‐solvents were investigated over a range of pH values (1–10) and shear rates (γ = 101−3 × 102 s−1). These PEEK suspensions generally exhibited a pseudoplastic flow behavior, indicating the occurrence of particle aggregation in the liquid medium. The maximum solids fraction (ϕm) showed an estimated value of ϕm = 2.9 wt %. Using a suspension with 3 wt % PEEK concentration, PEEK coatings on stainless steel substrates were obtained by EPD at constant voltage condition. The influence of the electrolyte conductivity on PEEK EPD from ethanol–isopropanol suspensions was studied. Experimental results showed that high‐conductivity ethanol‐based suspensions yield non‐uniform deposits, while low‐conductivity suspensions resulted in uniform coatings. The difference in the deposition behavior is due to the different pH of the suspensions and the relationship of pH with suspension conductivity. pH = 8 was the optimal value for this system in terms of deposition results. The surfaces of EPD PEEK coatings were homogenous and a qualitatively good adhesion between the PEEK deposits and the substrate was confirmed. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40953.

Mechanical and Tribological Properties of PEEK Coatings with Different Melt Indexes Prepared by Electrostatic Powder Spray Technique

Poly-ether-ether-ketone( PEEK) coatings with different melt indexes( MI) were prepared on the stainless steel substrate via electrostatic powder spraying method. Amorphous coatings were obtained by quenching the as-melted coatings into the ice-water medium. Semi-crystalline coatings were obtained by annealing the amorphous coatings in an oven for 30 min at 260 ℃. The XRD results indicates that the structure of PEEK coatings transforms from amorphous to semi-crystalline via the treatment of annealing. The hardness and the behavior friction of the PEEK coatings were tested. The result demonstrates that by the same treatment,the PEEK coatings with larger MI have higher crystallinity. The semi-crystalline PEEK coatings have higher hardness,lower friction coefficient and better wear rate than the amorphous ones. The poor fluidity of PEEK-A with lower MI leads to the rough coatings. Both of the PEEK-B and PEEK-C with larger MI can form smooth coatings and the friction coefficients and wear rates of them are stable. The friction coefficients of semicrystalline coatings B and C are less than 0. 15,and the wear rates are less than 20 ×10-6mm3/( N·m). Therefore PEEK with larger MI is more suitable for the preparation of PEEK coating by electrostatic spraying.