Showing papers on "Peek published in 2008"

Nanofiller‐reinforced polymer nanocomposites

Abstract: In this work, the technology of nano- and micro-scale particle reinforcement concerning various polymeric fiber-reinforced systems including polyamides (PAs), polyesters, polyurethanes (PUs), polypropylenes (pps), and high-performance/temperature engineering polymers such as polyimide (PI), poly(ether ether ketone) (PEEK), polyarylacetylene (PAA), and poly p-phenylene benzobisoxazole (PBO) is reviewed. When the diameters of polymer fiber materials are shrunk from micrometers to submicrons or nanometers, there appear several unique characteristics such as very large surface area to volume ratio (this ratio for a nanofiber can be as large as 103 times of that of a microfiber), flexibility in surface functionalities and superior mechanical performance (such as stiffness and tensile strength) compared to any other known form of the material. While nanoparticle reinforcement of fiber-reinforced composites has been shown to be a possibility, much work remains to be performed in order to understand how nanoreinforcement results in dramatic changes in material properties. The understanding of these phenomena will facilitate their extension to the reinforcement of more complicated anisotropic structures and advanced polymeric composite systems. Copyright © 2008 John Wiley & Sons, Ltd.

Microstructures and tribological properties of PEEK-based nanocomposite coatings incorporating inorganic fullerene-like nanoparticles

Abstract: The high strength, wear resistance and high operational temperature of polyetheretherketone (PEEK) have attracted increasing interests of this material for tribological applications. The addition of solid lubricant is an effective way to further improve the tribological properties of polymeric materials. In the present work, inorganic fullerene-like tungsten disulfide (IF-WS 2 ) nanoparticles were incorporated into PEEK coatings with the aim of reducing the coefficient of friction (COF) and improving the wear resistance of the coatings. The microstructures of IF-WS 2 /PEEK nanocomposite coatings were characterized using a combination of SEM, XRD and FTIR measurements. The thermal behaviours of the coatings were determined using differential thermal analysis (DTA). Tribological tests had also been carried out to evaluate the friction and wear behaviours of IF-WS 2 /PEEK nanocomposite coatings. The results showed that significant improvement can be achieved in the tribological properties of the nanocomposite coatings by incorporating IF-WS 2 nanoparticles.

Amorphous and crystalline polyetheretherketone: Mechanical properties and tissue reactions during a 3-year follow-up.

Abstract: The study was aimed to test the mechanical strength, structural stability, and tissue reactions of optically amorphous and crystalline polyetheretherketone (PEEK) plates during a 3-year follow-up in vivo and in vitro. The injection-moulded PEEK plates were implanted to the dorsal subcutis of 12 sheep, which were sacrificed at 6-156 weeks. Thereafter, the plates were subjected to tensile tests, and levels of crystallinity were assessed by differential scanning calorimetry (DSC). Histological evaluation was carried out using the paraffin technique. In vitro properties were examined with the tensile test and DSC at 0-156 weeks. Tissue reactions were mild and fairly similar for the amorphous and crystalline plates at corresponding points in time. The mechanical characteristics of the plates remained stable over the entire follow-up. The tensile yield load and elongation at the yield load of the crystalline plates were roughly double ( approximately 500 vs. 270 N and 2.4 vs. 1.4 mm, respectively) in comparison to the amorphous plates. The elongation at break load of the crystalline plates was smaller than that of the amorphous ones (6 vs. 10). The level of crystallinity in both the optically amorphous ( approximately 15%) and crystalline (32-34%) plates remained invariable during the follow-up. The in vitro and in vivo data coincided remarkably well. In conclusion, both optically amorphous and crystalline PEEK plates are suitable for the fixation of fractures and osteotomies.

Microhardness of PEEK/ceramic micro- and nanocomposites: Correlation with Halpin–Tsai model

Abstract: Microhardness of high performance PEEK matrix composites reinforced with micro- and nanosize ceramic particles of aluminum nitride and alumina was evaluated with Vickers hardness tester. The microhardness of composites increases with increasing ceramic particle loading. The microhardness of PEEK/AlN composites is higher than that of PEEK/Al2O3 composites. For a given volume fraction, the improvement in microhardness of nanocomposites is higher than that of microcomposites. For the first time, the Halpin–Tsai equation was applied to correlate the microhardness. It was found that the adjustable parameter, i.e. ξ, is different for both particles. The value of ξ is higher for nanocomposites compared to microcomposites.

Effects of bioactive glass and beta-TCP containing three-dimensional laser sintered polyetheretherketone composites on osteoblasts in vitro

Abstract: Because of their excellent physical properties nonresorbable thermoplastic polymers have become more important for the field of reconstructive surgery. Aim of the present study was to investigate the effects of laser sintered polyetheretherketone (PEEK) with incorporated osteoconductive and bioactive bone substitution materials on osteoblasts in vitro. Human osteoblasts (hFOB 1.19) were seeded onto laser sintered PEEK samples containing nano-sized carbon black, b-tricalciumphosphate (b-TCP), and bioactive glass 45S5. Osteoblasts were investigated for cell viability, cell proliferation and cell morphology. A constant proliferation of osteoblasts could be observed on all samples with the highest values for bioactive glass containing samples at day 7 (OD 1.76 6 0.22) and day 14 (OD 3.75 6 0.31) and lowest values for b-TCP containing probes throughout the study compared with the PEEK pure control group. Highest cell viability was observed for Bioglass containing probes (95.5 6 3.32)% whereas osteoblasts seeded on b-TCP containing probes showed reduced viability (84.4 6 4.32)%. Laser sintered PEEK implants seem to be attractive candidates for use as bone substitutes for reconstructive surgery because of their biocompatibility, individual shape, and the possibility of compounding bioinert polymer powder with osteoconductive and bioactive materials which might benefit bone formation in vivo.

Synthesis and characterization of homogeneously sulfonated poly(ether ether ketone) membranes: Effect of casting solvent

Abstract: Poly(ether ether ketone) (PEEK) was homogeneously sulfonated to have various degrees of sulfonation from 48 to 83%. The sulfonated PEEK (sPEEK) membranes were prepared by a solvent casting method using a few solvents such as N,N-dimethyl formamide, N,N-dimethyl acetamide, and 1-methyl-2-pyrrolidinone. The effect of casting solvent on the membrane morphology and properties was investigated. The sulfonation degree and ion exchange capacity were determined by a back titration method, and the morphology of membrane by SEM. It has been demonstrated that the surface morphology and properties of sPEEK membranes, such as water uptake, methanol permeability, ion conductivity, and mechanical strength, were considerably affected by the type of solvent, where the DMAC-sPEEK system showed the best performance in the polymer electrolyte membrane application for DMFC. This solvent effect on the membrane morphology and properties was caused by interaction strength (hydrogen bonding) between polymer and solvent. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Polyetheretherketone (PEEK) Coatings on Stainless Steel by Electrophoretic Deposition

Abstract: Polyetheretherketone (PEEK) particles were deposited on 316L stainless steel substrates by electrophoretic deposition (EPD) from ethanol suspensions producing uniform coatings. The process involved deposition of two layers and subsequent densification of the coating by sintering at 343 °C for 30 minutes. The microstructure and thickness of the coatings were reproducible demonstrating the convenience of EPD as a low-cost method to produce homogeneous PEEK films on metallic substrates.

Effects of environmental ageing on the static and cyclic bending properties of braided carbon fibre/PEEK bone plates

Abstract: The use of titanium and steel bone plates to fix fractured limbs can create problems due to stress shielding, bone resorption and subsequent refracture. Here, braided carbon fibre reinforced poly-ether-ether-ketone (CF/PEEK) was evaluated as a possible implant material that could reduce these problems. CF/PEEK bone plates were aged in a simulated body environment for up to 12 weeks and then mechanically tested in 3 and 4-point bending tests. Sample mass increased by around 0.3 wt.%, yet bending stiffness and strength remained unchanged. Scanning Electron Microscopy (SEM) showed no changes in failure modes with age. Braided CF/PEEK shows an excellent resistance to fatigue failure even after prolonged ageing, easily surpassing the fatigue life of commonly used stainless steel alloys such as 316L. In addition, CF/PEEK had half the stiffness of steel for the same static strength, which would reduce stress shielding. Together, the results suggest that CF/PEEK is a highly suitable material for bone plates and should be further investigated for this application.

Superhydrophobic PEEK/PTFE composite coating

Abstract: A simple and inexpensive method for forming a PEEK/PTFE superhydrophobic surfaces by controlling the topographical microstructures by adjusting the curing temperature has been proposed. The resulting porous surface, with ribbon-like randomly distributed double-scale structure and the lowest surface energy hydrophobic groups (-CF3) has a water contact angle of 161°.

Fracture simulation of CFRP laminates in mixed mode bending for hybrid Titanium-PEEK /AS4 composites

Abstract: This paper analyses the progressive mixed mode delamination failure in unidirectional and multidirectional composite laminates using fracture experiments, finite element (FE) simulations and an analytical solution. The numerical model of the laminate is described as an assembly of damageable layers and bilinear interface elements subjected to mixed mode bending. The analytical approach is used to estimate the total mixed mode and decomposed fracture energies for laminates with different stacking sequences, which is also validated through experiments. It is concluded that the interlaminar fracture toughness of multidirectional laminates is considerably higher than that of the unidirectional ones. The effect of initial interfacial stiffness and element size is studied and it is also shown that their value must not exceed a definite limit for the numerical simulations to converge. The model can also be further extended to simulate the mixed mode fracture in hybrid fiber metal laminates.

Implant articular surface wear reduction system

Abstract: An implant articular surface wear reduction system improves orthopedic prosthetic joint longevity by reducing frictional abrasive wear. The system includes a polymeric implant component and a rigid implant component. A hard wear layer is attached to the polymeric implant. The hard wear layer represents one opposing articular surface of a joint. The rigid implant component has a working surface and may represent another opposing articular surface in the joint. In one embodiment, the rigid implant component and the hard wear layer are ceramic. In another embodiment, a non-metallic wear layer is attached to the working surface. The non-metallic wear layer represents another opposing articular surface of the joint. In one embodiment, the polymeric implant component is a tibial implant and the rigid implant component is a femoral implant and the non-metallic wear layer is a polymer, such as polyethylene, self-reinforced polyphenylene, or PEEK.

Thermal expansion behaviour of high performance PEEK matrix composites

Abstract: The thermal expansion behaviour of high performance poly(ether-ether-ketone) (PEEK) composites reinforced with micro- (8 µm) and nano- (39 nm) sized Al2O3 particles was studied. The distribution of Al2O3 in the PEEK matrix was studied by scanning electron microscopy and transmission electron microscopy. The coefficient of thermal expansion (CTE) was reduced from 58 × 10−6 °C−1 for pure PEEK to 22 × 10−6 °C−1 at 43 vol% micro-Al2O3 and to 23 × 10−6 °C−1 at 12 vol% nano-Al2O3 composites. For a given volume fraction, nano-Al2O3 particles are more effective in reducing the CTE of composites than that of micro-Al2O3 particles. This may be attributed to the much higher interfacial area or volume of nanocomposites than that of microcomposites. The upper limit and lower limit of the Schapery model separately fit closely the CTE of the micro- and nano-composites, respectively. Other models such as the rule of mixture and Kerner and Turner models were also correlated with the data.

Mechanical behaviors of Al2O3 nanoparticles reinforced polyetheretherketone

Abstract: In order to improve the mechanical properties of Polyetheretherketone (PEEK), nanometer Al2O3 particles were used as fillers. The effect of size and content of Al2O3 particles, various coupling agents and dispersing methods on the mechanical properties were all studied. The reinforced PEEK filled with 15 nm and 5 wt.% Al2O3 particles possessed higher tensile, flexural and impact performance than that filled with 90 nm and 10 wt.% Al2O3 particles possessed. Especially, the impact strength of the PEEK filled with titanate treated nanometer Al2O3 particles was about eight times that of neat PEEK. Furthermore, the higher tensile, flexural, compression and impact strength of PEEK filled with nanometer Al2O3 particles than that of PEEK filled with nanometer SiO2 particles were presented. In addition, through the analysis of fractographs for tensile specimens by scanning electrical microscope (SEM), the relativity between mechanical characteristics and fracture mechanism were discussed.

The application of PEEK in stainless steel fiber and carbon fiber reinforced composites

Abstract: The mixing ingredient of the semi-metallic friction material – stainless fiber and carbon fiber reinforced polyether-ether-ketone (PEEK) – its hot-molding process, friction performance and wear resistance are studied in this paper. The friction and wear mechanism was analyzed through observing the worn surface morphology by scanning electron microscope (SEM) at different temperatures, and is further confirmed with X-ray diffraction (XRD) and infrared spectrometry (IR) analysis. The results showed that the developed materials have stable friction coefficients and lower wear ratio. The wear mechanism is that the particle abrasion occurs at low-temperature, the adherence abrasion and particle abrasion take place at the temperature between 200 and 350 °C. The transferred layer is formed, and big debris particles of lath-shape and sheet-shape are found on the worn surface. The thermal degradation of the PEEK does not occur until its temperature rises to higher than 350 °C. The stainless steel and carbon fibers bind strongly with the matrix and have good abrasive resistance, improving stability of the friction coefficients of the materials.