PEEK Polymers Research Articles

Modifications of structural, optical and chemical properties of Li3+ irradiated polyurethane and polyetheretherketone

Thin membranes of PU and PEEK polymers were irradiated with 50MeV lithium ions for modifications in structural, optical and chemical properties. The XRD spectra indicated the alignment of polymeric chains in a regular pattern and hence there was decrease in the amorphous character of the irradiated polymers. The optical absorption of all irradiated samples shifted towards the visible region of the spectrum. It was attributed to the generation of a conjugated system of bonds which lowered the band gap energy of irradiated samples. The FTIR spectra obtained after irradiation exhibited decrease in absorbance for various bands in case of PU whereas PEEK showed minor changes in its chemical properties. The other results were discussed from the calculated parameters such as crystallite size, Urbach's energy and number of carbon hexagon rings per conjugation length from the analyses of the XRD and UV–visible data.

PEEK polymers for more efficient transmissions and optimised gear shifting

PEEK polymers for more efficient transmissions and optimised gear shifting

Synthesis and Modification of Poly(ether ether ketone) and their Properties: A Review

Synthetic aromatic polyarylether ketones are known for their high performance applications. Poly(ether ether ketone) is an important material which is most widely used in such aggressive environments as nuclear plants, oil and geothermal wells, chemical plants, and high-pressure steam valves. Considering the wide range of properties of PEEK polymers, a variety of structurally modified PEEK polymers are also reported. This review covers the detail of different synthetic and modification procedure, the characterization technique applied on PEEK. In brief, morphological and related properties are also described.

Hybrid SPEEK/Phosphonatedsilsesquioxanes membranes for PEMFC

In this work, the production and characterization of hybrid membranes of sulfonated poly(ether-ether-ketone; SPEEK) and phosphonated copolysilsesquioxanes (PCs) and its application in proton exchange membrane fuel cell (PEMFC) were studied. To improve the proton conduction and thermal stability of the polymer SPEEK, PCs were synthesized from diethylphosphatoethyltriethoxysilane (Ph-TEOS) and phenyltriethoxysilane (PTES), 90/10 mol/mol, by a hydrolysis/condensation procedure. The PCs were characterized by infrared thermal analysis. Hybrids membranes produced from SPEEK and 20 wt% PC were submitted to further hydrolysis to give semiinterpenetrating copolysilsesquioxanes networks. The hybrid membranes were also characterized according to their thermal behavior, proton conductivity, electrochemical performance in fuel cell, and oxidative stability. The proton conductivities (σ) of the membranes in the hydrated state at room temperature were determined by electrochemical impedance spectroscopy. It was verified that the proton conductivities of the hydrolyzed hybrid membranes were about 370% higher than the σ of plain SPEEK. The hydrolyzed membranes with 20% (90:10) PC showed the best performance in a PEMFC working with H2/O2at 60°C.

Development of Advanced Thermoplastic Composite Projectiles for High-Velocity Shots With the PEGASUS Railgun

The work presented here aimed at developing advanced thermoplastic composite laminates specifically dedicated to the fabrication of brush-armature supporting structures for the PEGASUS railgun of the French-German Research Institute of Saint-Louis. The main objective is to surpass the results obtained previously with glass-fiber-reinforced epoxy composites. Due to higher ductility and superior dynamic behavior of PEEK polymers, an S2-glass woven fabric preimpregnated with a PEEK resin was selected. The interlaminar resistance and tensile behavior of the material was characterized experimentally. The results led to the identification of the most suitable fiber/resin ratio and fabrication process for thick laminates. Several prototypes weighing about 320 g were produced and used for six shots with the PEGASUS railgun. Already in the first series of experiments, the laminates show a remarkable mechanical resistance, and a maximal velocity of 2440 m/s was obtained.

Synthesis, mechanical properties and chemical/solvent resistance of crosslinked poly(aryl-ether–ether–ketones) at high temperatures

A synthetic two-stage procedure was developed for the synthesis of moderately crosslinked polymers based on poly(aryl-ether–ether–ketone) (PEEK). Rigid crosslinks based on aromatic imines were synthetically introduced into PEEK polymer matrix resulting in PEEK materials with various degrees of crosslinking. Two specific crosslinked PEEK polymers (5% and 10% of ketone groups crosslinked) were characterized and studied in detail. Thermomechanical properties, as well as chemical/solvent resistance of these materials at high temperatures (175–280 °C) were investigated and compared to the original PEEK material (Victrex 151G). The introduction of rigid crosslinks was shown to disrupt crystallinity of PEEK very efficiently. Because tensile properties of PEEK depend on its crystallinity, we observed a decrease in properties such as Young's modulus and the ultimate elongation, the extent of which depended on the degree of crosslinking. We also observed an improvement in the elastomeric properties of the crosslinked materials, such as decrease in initial permanent set during high temperature cyclic tensile testing. Mechanical creep behavior at high temperature also improved for crosslinked polymers vs the original commercial Victrex 151G in terms of a reduced irreversible creep component. All crosslinked materials showed excellent resistance to hot oily, acidic and basic environments, as well as excellent thermal stability. Overall, we were able to synthesize “softer” materials that are more rubbery at high temperature than commercial thermoplastic Victrex 151G; these elastomer-like materials showed promising mechanical properties for high temperature applications in hot/corrosive environments.

Macroporous polymers from particle-stabilized emulsions

Macroporous polymers are attractive materials due to their low density, low cost, recyclability and tunable mechanical and functional properties. Here, we report a new approach to prepare macroporous polymers from emulsions stabilized with colloidal polymeric particles in the absence of chemical reactions. Stable water-in-oil emulsions were prepared using poly(vinylidene difluoride) (PVDF), poly(tetrafluoroethylene) (PTFE), and poly(etheretherketone) (PEEK) as stabilizing polymeric particles in emulsions. The partial wetting of the polymeric particles by the two immiscible liquids drives particles at the water–oil interface during emulsification, leading to extremely stable water-in-oil emulsions. The particle-stabilized emulsions were processed into highly porous solid polymer components upon drying and sintering. The high stability of emulsions also allows for the preparation of hollow polymeric microcapsules. We describe the conditions required for the adsorption of particles at the liquid–liquid interface, we show the rheological behavior of the polymer-loaded wet emulsions and, we discuss the effect of the emulsions' initial compositions on the final sintered porous structures. This new approach for the fabrication of macroporous PVDF, PTFE, and PEEK polymers is particularly suited for the preparation of porous materials from intractable polymers but can also be easily applied to a variety of other polymeric particles.

Design and performance of a high pressure insert for use in a standard magic angle spinning NMR probe

In this paper we describe the construction and performance of high pressure magic angle inserts made from the polymer PEEK. The inserts were designed to fit inside standard commercial 7 mm magic angle spinning rotors and spin at the maximum frequency of the probe. The sample volume of the inserts was 100 μL. A gas loading chamber that operates at room temperature is described. The performance of the inserts is discussed for a number of gases in terms of resolution as a function of spinning speed and leakage of the gas due to permeation through the polymer. Finally, some preliminary results are shown in relation to complex food materials.

Sulphonated poly(ether ether ketone) membranes for fuel cell application: Thermal and structural characterisation

Sulphonated PEEK polymers with a different sulphonation degree (DS) were obtained by varying the sulphonation reaction temperature. Ionomeric membranes were prepared by using different solvents (DMSO, DMAc, DMF and DMAc/DMF mixture). Structural and chemical–physical film characterisations were carried out by X-ray and thermo gravimetric analyses. Membranes obtained from DMF and/or DMAc have a low crystallinity with an amorphous structure, while the DMSO–sPEEK membrane has a more crystalline structure that could inhibit proton conduction. The efficient proton conducting structure for sPEEK chains seems to be the statistical coil. The analysed membranes do not present any ionomer or matrix peak associated with the clustering of sulphonic groups or phase separation due to the statistical distribution of the sulphonic groups on the main PEEK chain. The thermal behaviour was investigated by a differential scanning calorimetry (DSC). From a cooling analysis all the water contained in the membranes was shown to be strongly linked to sulphonic groups and of a non-freezable type. The influence of the casting solvent on the cell performance was studied. The developed membranes were also tested in H 2/air single cell in the temperature range 80–130 °C. A maximum power density of about 400 mW cm −2 at 0.5 V was reached at 130 °C.

Synthesis and properties of thio‐containing poly(ether ether ketone)s

AbstractA series of thio‐containing poly(ether ether ketone) (PEESK) polymers was synthesized by the introduction of thio groups from 4,4′ thiodiphenol (TDP) into the poly(ether ether ketone) (PEEK) structure via reaction between the phenol and aromatic fluoride groups. The effect of the thio groups on the properties of the PEESK materials was investigated. Differential scanning calorimetry (DSC) analysis and X‐ray diffraction (XRD) patterns show a depression in the crystallinity of the PEESKs with incorporation of the content of thio groups in the backbones. The crystalline structure was identified as an orthorhombic structure with lattice constants of a = 7.52 Å, b = 5.86 Å and c = 10.24 Å for all crystallizable PEESKs. The crystalline structures of the thio‐containing PEEK polymers were the same as that of the neat PEEK, which means the thio‐containing block in the whole thio‐containing PEEK molecule is almost excluded from the crystalline structure and the crystals are completely formed by ‘non‐thio’ blocks only. Due to the glass transition temperature (Tg) and melting temperature (Tm) depression with increase in the TDP content in the reaction system, the processability of the resultant thio‐containing PEEKs could be effectively improved. Copyright © 2004 Society of Chemical Industry

Recent advances in ceramic-polymer composite electrets

Recent work on ceramic-polymer composites for piezoelectric and pyroelectric applications is presented with special regard to the production and characterisation of new composite materials as well as two new applications of these composite materials. One of these composites is made using ceramic powders obtained using the sol-gel technique. This technique allows a better control of the stoichiometry as well as a lower temperature of crystallisation as compared with the conventional mixed oxides route. A better control of powder morphology also produces ceramic grains in the submicron range enabling the production of nanocomposites with electroactive properties. A second type of composite is reported using high temperature polymer PEEK, thus extending the temperature range of common electroactive composite materials. Finally the use of these materials is demonstrated in two piezoelectric applications, an angular acceleration accelerometer and an acoustic emission sensor.

Developments with the oscillating capillary nebulizer—effects of spray chamber design, droplet size and turbulence on analytical signals and analyte transport efficiency of selected biochemically important organoselenium compounds

Silica and polymer PEEK® capillaries were used to modify an oscillating capillary nebulizer (OCN) in order to make it sturdier and more durable for routine analyses, and also to improve response sensitivity. The performance of four modified OCNs was compared to that of the original OCN design and also to a Meinhard High Efficient Nebulizer (HEN), using an identical single-pass cylindrical spray chamber for all the nebulizers. The effects of spray chamber design, droplet size and turbulence on analyte transport efficiency of low molecular weight organoselenium compounds were also investigated. Three organoselenium standards: (1) selenocystamine; (2) selenomethionine; and (3) trimethylselenonium iodide were used as test compounds with inductively coupled plasma-mass spectrometry (FI/ICP-MS). Droplet size distributions and Sauter mean diameters of aerosols were measured by laser Fraunhofer diffraction. An OCN fabricated with PEEK® gas capillary, with either a thicker capillary wall or a larger inner diameter liquid capillary tube, performed better than the original OCN design. The optimal improvement of analytical signal of 3–4 times, corresponding to a 2.5–3.0 times improvement in analyte transport efficiency was found, compared to the original OCN design and also to a standard Meinhard HEN. Contrary to literature reports, we observed that moderate increases in mean droplet sizes resulted in improved analyte transport efficiencies and higher signal intensities for the volatile compounds tested. However, nebulizers producing aerosols with Sauter mean diameters, D[3,2], greater than approximately 9.5 µm gave lower transport efficiencies and reduced signal intensities. Although greater turbulence in the gas flow inside a single-pass spray chamber predictably decreased net analyte transport efficiencies, the overall loss of aerosol was unexpectedly 3–5 times greater for small droplets ( 3 µm, <9 µm).

Thermal expansion behaviour of thermoplastic composites

The thermal-expansion behaviours of a variety of thermoplastic composites based on the ICI Victrex polymers PEEK, ITA, HTA and ITX are examined. It is shown that when each of the composites is raised above the glass-transition temperature, Tg, of the polymer matrix considerable permanent distortion occurs in the small samples used, though the effect is not evident below Tg. This is attributed to relaxation of process-induced residual stresses generated in the larger plates from which the samples were prepared. A number of models are used to calculate the thermal-expansion behaviour of the fibres transverse to their long axes; the results are shown to be inconsistent, and in poor agreement with directly measured properties. Finally, the utility of the data for calculation of thermal-expansion behaviour parallel to the fibres in the composites is considered.

Comments on "Electric breakdown strength of aromatic polymers-dependence on film thickness and chemical structure" [with reply

For original paper by B. Helgee and P. Bjellheim see ibid., vol.26, no.6, p.1147-52 (Dec. 1991). The commenter discusses the influence of partial discharges on the breakdown field strength of the aromatic polymers PI, PEI, PET, PEEK and PES and its role in the findings of B. Helgee and P. Bjellheim. The author's reply is included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ion implantation of polymers for electrical conductivity enhancement

The polymers PET, PAN, PES and PEEK were implanted with ions of He, B, C, N, Ar and As at an energy of 50 keV. PEEK was implanted with I at 22.5 MeV, Xe at 24 MeV, and Ni at 47 MeV. Surface resistivity for electrical conduction indicated a plateau effect in the dose range 10 16–10 17 ions/cm 2. The more aliphatic polymer, PET, indicated the lowest resistance of the low energy implants. The high energy ions produced much lower resistivities at much lower doses. The temperature dependence of the resistivities indicate a quasi-one-dimensional variable range hopping mechanism for electrical conduction.

The preparation of poly(aryl ether ketones) by the use of trifluoromethanesulfonic acid

Two synthetic routes were used for the preparation of aromatic poly(ether ketones): Friedel-Crafts acylation and aromatic nucleophilic substitution. The first route involved the reaction of diphenyl ether and terephthalic acid dichloride in trifluoromethane-sulfonic acid. The addition of trifluoromethanesulfonic anhydride or phosphorus pentoxide resulted in increased molecular weights. The second synthetic route involved the synthesis of an amorphous tert -butyl-substituted poly(ether ketone) prepolymer. Subsequently, the tert -butyl groups were removed by a reversed Friedel-Crafts alkylation reaction yielding the crystalline polymer PEEK. The dealkylation reaction was performed in trifluoromethanesulfonic acid. The addition of a tert -butyl group acceptor resulted in high dealkylation conversions.

Fatigue properties of unidirectional carbon fibre composites at cryogenic temperatures

Design engineers working with composite materials are still confronted with uncertainties as to their fatigue behaviour, especially for cryogenic applications. In the course of cooling, different thermal contraction of the fibre and matrix gives rise to thermal stresses and strains which influence most of the mechanical properties. In this paper, the fatigue behaviour of unidirectional (UD) composites with different fibres and matrices will be described. A first step in understanding the failure mechanism under cyclic loading will be presented. In earlier tests excellent fatigue properties were found for carbon fibre UD composites made of T300 carbon fibres and an epoxy matrix 1,2. However, the applied epoxy resin was brittle, especially at low temperatures. Therefore the brittle resin was substituted by polycarbonate (PC), a tough thermoplastic polymer 3,4. Nevertheless, for a composite with that matrix the fatigue endurance limit, normalized to the static strength, was found to be much lower (43%). SEM studies illustrated a poor fibre - matrix bond. To determine the bond's influence on fatigue properties, another tough matrix system was tested. The polymer PEEK is known to build a strong bond to carbon fibres, initiated by crystal growth onto the fibre surface 4,5. However, investigations on the fatigue behaviour of this composite at 77 K yielded the same low fatigue endurance limit as was found for the carbon fibre - PC system 4. At this point it can be concluded that the poor fatigue behaviour is not necessarily due to a strong or poor fibre - matrix bond. It is the purpose of this work to examine whether this different fatigue behaviour is due to matrix failure.

Variations in the crystal lattice of PEEK and related para-substituted aromatic polymers: 1. Thermal expansion

Uniaxially oriented films of PEEK have been examined by X-ray diffractometry over the temperature range 20 to 290°C in order to determine the expansion of the crystal lattice. The a and b lattice parameters were measured from equatorial scans using the 110, 200 and 020 reflections and the c parameter from meridional scans using the 002 reflection. The expansion rate in the a direction is about three times that of the b direction, while the change in c is almost negligible. Close to the T g at around 145°C, there is an increase in the expansion coefficient of a and a reduction in the b coefficient. The overall expansion of the cell volume is essentially linear with a volume expansion coefficient of 1.65 × 10 −4°C −1.

Variations in the crystal lattice of PEEK and related para-substituted aromatic polymers: 2. Effect of sequence and proportion of ether and ketone links

The crystal lattice constants have been measured for PEEK and the related aromatic polymers PEEKEK, PEK, PEEKK, PEKEKK and PEKK. Measurements were made on uniaxially oriented film samples using the 110, 200 and 020 reflections from X-ray equatorial scans to determine the a and b parameters and using the 006 and 008 from meridional scans to determine c. All polymers are able to crystallize with a PEEK type cell, although the b and c parameters increase with the proportion of ketone links. At higher ketone content a new crystal form is able to occur alongside the normal PEEK cell. The new cell was the dominant form in the PEKK sample. The new cell in PEKK is orthorhombic with parameters a = 4.17 ± 0.02 A ̊ , b = 11.34 ± 0.04 A ̊ , c = 10.08 ± 0.01 A ̊ and density 1.395 ± 0.008 g ml −1. It is proposed that the new cell has the same symmetry, chain conformation and relative chain packing as the normal PEEK cell, but with a reduced and b enlarged.

Positron annihilation spectroscopy for chemical analysis: A novel probe for microstructural analysis of polymers

Positron annihilation spectroscopy for chemical analysis (PASCA) has been developed to analyze the microstructure of polymers. Positron annihilation lifetime measurements give direct information about the dimension and contents of free-volume holes in amorphous materials. The angular correlation measurements of positron annihilation radiation give additional information about the shape of the free-volume holes in oriented polymeric materials. The unique capability of PASCA to probe free-volume properties is from the fact that positronium atom is trapped in the atomic-scale holes which have a size ranging from 1 to 10 Å. Theoretical aspects, experimental developments of PASCA, and examples in analyzing the microstructures of epoxy, PEEK, and PMMA polymers are presented.