Search

Silica hollow tube (SHT) nanofillers were fine distributed in poly(ether ketone ketone) (PEKK) to serve decently as sixth generation (6G) substrate films. Distinctly lower dielectric and thermal expansion characteristics were detected for all PEKKaxSHTy film sequence filled with proper amounts of SHT nanofillers. The dielectric characteristics detected for all PEKKaxSHTy film sequence diminished to a minimum, as SHT loads came near an optimal value of 8wt%. The LCTE evaluated for each PEKKaxSHTy film sequence reduced distinctly with increasing SHT loads. Suitable dielectric constant (εr) (2.26 at 1 MHz), and/or dielectric loss (tan δ) (0.0027 at 1 MHz) and/or Linear coefficient of thermal expansion (LCTE) (30.5 × 10−6/ °C) for 6G rapid-speed communication were detected for PEKKP700092SHT8 substrate film having 8wt% load of SHT nanofillers. Meanwhile, the beginning degradation temperatures estimated for all PEKKaxSHTy film sequence increased distinctly with increasing SHT loads. All free-volume-cavity characteristics estimated for all PEKKaxSHTy film sequence approached a highest value, as SHT loads came near an optimal value of 8wt%. Distinctly lower εr and tan δ were detected for PEKKa and PEKKaxSHTy having higher free-volume-cavity characteristics. Possible interpretations for the distinctly diminished dielectric and/or heat-resistant characteristics acquired for PEKKaxSHTy films are presented. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An efficient way to reduce direct operating costs in aerospace applications is to lower the overall weight. In this context, thermoplastic composites offer a high potential for weight reduction. However, their application requires time and cost-optimized process technologies. Thermoplastic tape laying with subsequent out-of-autoclave consolidation represents such a process technology. Typical process chains consist of several automated steps that can influence the component's quality. Hence, a cross-process approach is applied to identify relevant process parameters. This paper focuses on minimizing the gaps between parallel-placed tapes and thereby reducing their influence on the laminate's porosity. A geometrical model is developed and validated to predict the maximum gap sizes for a tape-laying process as a function of process accuracy, material accuracy, and process parameters. Based on this, a methodological approach is presented to minimize the influence of gaps on porosity. It is validated using automated tape laying and a novel low-pressure consolidation process. The findings make an important contribution to understanding the development of porosity along the process chain for the manufacture of thermoplastic composites for aerospace applications. It can be shown that the approach enables the prediction of gap sizes and allows to minimize their influence on porosity. [ABSTRACT FROM AUTHOR]

Quaternary ammonium salt modified montmorillonite (QASMMT) nanoplatelets were well dispersed in poly(ether ketone ketone) (PEKK) polymers to make pleasing fifth generation (5G) substrates. Substantially smaller dielectric properties and linear thermal expansion coefficient (LCTE) were found for each PEKKaxQASMMTy film series filled with small and appropriate QASMMT loadings. The dielectric constant (εr) and dielectric loss (tan δ) values acquired for each PEKKaxQASMMTy film series reduced to a lowest value as QASMMT loadings approached 3 wt%. Satisfactory εr (2.59, 2.71, and 2.80 at 1 MHz), tan δ (0.0032, 0.0038, and 0.0042 at 1 MHz) and LCTE (∼36.8×10−6/°C, 38.8×10−6/°C and 40.5×10−6/°C) for 5G communication were acquired for PEKKax QASMMT3 films filled with only 3 wt% optimum loading of QASMMT nano-platelets. In the meantime, the onset degradation temperatures acquired for each PEKKax QASMMTy film series increased substantially with increasing QASMMT loadings. All free volume properties, such as, the radius of the free-volume-cavity or free-volume-cavity numbers per unit volume evaluated for every PEKKax QASMMTy film sequence enlarged to a largest value, as QASMMT loadings approached an appropriate value of 3 wt%. Substantial smaller εr and tan δ were acquired for PEKKa and PEKKax QASMMTy with larger free volume properties. Possible reasons accounting for these substantially diminished dielectric and LCTE properties of PEKKax QASMMTy films are proposed. [ABSTRACT FROM AUTHOR]

Nano-SiO2 particles have been incorporated into high-performance poly(ether ketone ketone) (PEKK) polymers to prepare satisfactory nanocomposite substrates for fifth-generation (5G) communication. Significantly lower dielectric constant (εr), dielectric loss (tan δ), and linear coefficient of thermal expansion (CTE) were found for each PEKKaxSiO2y nanocomposite film series incorporated with proper loadings of nano-SiO2 particles. The dielectric characteristics measured for each PEKKaxSiO2y nanocomposite film series decreased to a minimum as the nano-SiO2 loading approached an optimum value. Satisfactory εr (2.74 at 1 MHz), tan δ (0.00309 at 1 MHz), and linear CTE (~ 37 × 10−6/°C) for 5G high-speed communication were found for the nanocomposite film modified with the optimum nano-SiO2 loading of 10 wt.%. The porosity values measured for each PEKKaxSiO2y film series remained nearly zero then increased abruptly as the nano-SiO2 loading exceeded 10 wt.%. The free volume characteristics evaluated for each PEKKaxSiO2y film series increased to a maximum as the nano-SiO2 loading reached the optimum value of 10 wt.%. Possible explanations for the noticeably reduced dielectric and linear CTE characteristics found for PEKKaxSiO2y composite films are proposed. [ABSTRACT FROM AUTHOR]

Semicrystalline poly(aryl ether ketone)s (PAEKs) represent an industrially important class of high‐performance engineering thermoplastics with excellent physicochemical and mechanical properties, and the synthesis of PAEKs with enhanced glass transition temperatures (Tg) and moderate melting temperatures (Tm) is highly desirable. In the work reported, novel poly(ether ketone ketone)s (PEKKs) containing 1,4‐naphthylene units in main chains were synthesized by Friedel–Crafts solution copolycondensation of terephthaloyl chloride with a mixture of diphenyl ether and 1,4‐di(4‐phenoxybenzoyl)naphthalene (1,4‐DPOBN). The polymerization proceeded smoothly in 1,2‐dichloroethane in the presence of anhydrous AlCl3 and N‐methylpyrrolidone under mild conditions and afforded polymers having inherent viscosities of 0.66–0.98 dL g−1. The polymers with 5–30 mol% 1,4‐DPOBN are semicrystalline and have obviously enhanced Tg over commercial poly(ether ether ketone)s and PEKKs due to the incorporation of rigid and bulky 1,4‐naphthylene moieties into the main chain. The polymers with 20–30 mol% 1,4‐DPOBN not only have high Tg of 175–177 °C, but also relatively low Tm of 331–336 °C, having high potential for melt processing. The polymers with 20–30 mol% 1,4‐DPOBN also exhibit excellent thermal stability and good mechanical and solvent‐resistance properties. © 2021 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract Graphene and carbon black have been dispersed in a high performance thermoplastic polymer, the poly(ether ketone ketone), to improve its electrical conductivity. The dispersion of graphene has a significant influence on the percolation threshold. A simple exfoliation protocol to obtain graphene monolayers has led to a significant decrease of the percolation threshold from 4.2 to 1.9 vol%. To the best of our knowledge, it is one of the lowest percolation values for unfunctionalized graphene dispersed by melt blending in a high performance thermoplastic matrix. The conductivity value above the percolation threshold (1.2 S·m−1) means that graphene was not degraded during the elaboration process. Below the percolation threshold, Maxwell-Wagner-Sillars phenomenon increases the dielectric permittivity from 2.7 to 210 for PEKK/6 vol% graphene at 180 °C and 1 Hz. Dynamic mechanical analyses have shown that mechanical moduli were not significantly modified by conductive particles until 6 vol%. [ABSTRACT FROM AUTHOR]

Abstract To quantify the isothermal crystallization kinetics of poly(ether ketone ketone) (PEKK), the integration of the crystallization peak measured using differential scanning calorimetry is rendered difficult due to the thermal transient effects at the start of enthalpy recording. The different attempts to extrapolate this peak beginning often lead to false values of the Avrami exponent. A new crystallization kinetic assessment method is established here based on the derivative of the Hillier crystallization kinetic model. This method consists of directly fitting the transformation rate to the heat flow of the experimental crystallization, thus avoiding the extrapolation of the crystallization peak beginning. This method is successfully applied to two different PEKK grades with different crystallization kinetics. The identified crystallization parameters are modelled as a function of the crystallization temperature, and based on these modeling results, time-temperature-transformation diagrams of crystallinity were built to provide a useful tool for PEKK processing. Graphical abstract Image Highlights • Method is based on derivative expression for crystallization Hillier model. • Model fitting directly on the crystallization heat flux measured by DSC. • The method avoids the extrapolation of the crystallization peak beginning. • PEKK Crystallization kinetic modeling including primary and secondary crystallization. [ABSTRACT FROM AUTHOR]

A new monomer containing naphthalene and sulfone groups, 4,4′-bis(1-naphthoxy)diphenylsulfone (BNODPS), was easily prepared by the condensation reaction of 4,4′-dichlorodiphenylsulfone with 1-naphthol in the presence of base in dimethyl sulfoxide. Novel copolymers of poly(ether ketone ketone) and poly(ether sulfone ether ketone ketone) containing 1,4-naphthylene moieties were synthesized by the electrophilic Friedel–Crafts acylation copolycondensation of terephthaloyl chloride with a mixture of diphenyl ether (DPE) and BNODPS, over a wide range of DPE/BNODPS molar ratios, in the presence of anhydrous AlCl3 and N-methylpyrrolidone (NMP) in 1,2-dichloroethane. The polymers obtained were characterized by different physicochemical techniques. The copolymers with 5–25 mol% BNODPS are semicrystalline and had remarkably increased Tgs and decreased Tms over the wholly para-linked poly(ether ketone ketone) due to the incorporation of bulky and rigid 1,4-naphthylene moieties and flexible sulfone linkages in the main chains. The copolymer VI with 25 mol% BNODPS had not only high Tg of 185°C but also moderate Tm of 335°C, having good potential for melt processing. The copolymer VI had tensile strength of 102.2 MPa, Young’s modulus of 2.78 GPa, and elongation at break of 15.9% and exhibited high thermal stability and good resistance to organic solvents. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric nanocomposites based on poly(ether ketone ketone) (PEKK) and sodium niobate (NaNbO 3 ) particles were elaborated. The presence of submicronic particles does not influence the thermal stability of the matrix so that no degradation phenomenon is observed before 500 °C. The conservative mechanical modulus G ′ increases linearly with the NaNbO 3 fraction; this variation is well fitted by the Kerner model until 20 vol%. Such nanocomposites remain ductile. The polarizing field required for obtaining piezoelectric nanocomposites is 12 kV·mm − 1 i.e. analogous with the one used for poling bulk ceramic. The value of the piezoelectric coefficient ( d 33 = 0.2 pC·N −-1 for 20 vol% NaNbO 3 ) is consistent with the Furukawa's model. This value is explained by the low PEKK permittivity. This low d 33 is counterbalanced by the piezoelectric voltage constant ( g 33 = 103·10 − 3 Vm·N − 1 ) which is higher than the one of classical piezoelectric ceramic like PZT or BaTiO 3 . [ABSTRACT FROM AUTHOR]

Polyaryletherketones (PAEKs) are a class of ultrahigh performance polymers with outstanding temperature and chemical resistance. Poly(ether ketone ketone) copolymer (Kepstan®) and poly(ether ether ketone) (PEEK) display intrinsic insolubility in nearly all organic solvents. The primary issue for the application of these polymers is their processability which requires a high temperature/pressure-based technique, or the use of harsh and corrosive solvents, like methanesulfonic and sulfuric acid, resulting in sulfonation of the polymer backbone that adversely might affect their chemical stability. In this work, we propose a method to prepare porous Kepstan® and PEEK membranes using N -methyl-2-pyrrolidone (NMP) as solvent at room temperature. It consisted of a modification-regeneration strategy to turn commercial semi-crystalline Kepstan® and PEEK into dithiolane soluble derivatives that allow the fabrication of hollow fiber, flat-sheet, and electrospun nanofibers. The resulting membranes are then regenerated to the solvent-resistant materials. The novel Kepstan® and PEEK hollow fibers exhibited a N,N -dimethylformamide (DMF) permeance of 2.21 and 2.05 L m−2 h−2 bar−1, with more than 90% rejection of Crystal Violet (408 g mol−1) and Methyl Orange (327 g mol−1), respectively. [Display omitted] • Porous PEKK and PEEK hollow fiber membranes spun without strong acids at room temperature. • Solvent and temperature-resistant hollow fibers from commercial PEKK and PEEK. • Effective separation of molecules in the range of 327–408 g mol−1 in dimethylformamide. • Chemical modification-regeneration strategy to promote the polyketone processability. [ABSTRACT FROM AUTHOR]

A new monomer containing sulfone and imide linkages, bis{4-[4-( p-phenoxyphenylsulfonylphenoxy)benzoyl]-1,2-benzenedioyl}- N, N, N′, N′-4,4′-diaminodiphenyl ether (BPSPBDADPE), was prepared by the Friedel-Crafts reaction of bis(4-chloroformyl-1,2-benzenedioyl)- N, N, N′, N′-4,4′-diaminodiphenyl ether with 4,4′-diphenoxydiphenyl sulfone. Novel copolymers of poly(ether ketone ketone) and poly(ether ketone sulfone imide) were synthesized by electrophilic Friedel-Crafts solution copolycondensation of terephthaloyl chloride with a mixture of DPE and BPSPBDADPE. The polymers were characterized by different physico-chemical techniques. The polymers with 10-25 mol% BPSPBDADPE are semicrystalline and had increased Ts over commercially available PEEK and PEKK (70/30) due to the incorporation of sulfone and imide linkages in the main chains. The polymer IV with 25 mol% BPSPBDADPE had not only high T of 194 °C but also moderate T of 338 °C, having good potential for melt processing and exhibited high thermal stability and good resistance to common organic solvents. [ABSTRACT FROM AUTHOR]

A new monomer, bis[4-(p-phenoxybenzoyl)-1,2-benzenedioyl]-N,N,N′,N′-4,4′-diaminodiphenyl sulfone (BPBDADPS), was prepared by the Friedel–Crafts reaction of bis(4-chloroformyl-1,2-benzenedioyl)-N,N,N′,N′-4,4′-diaminodiphenyl sulfone (BCBDADPS) with diphenyl ether (DPE). Novel poly(aryl ether ketone)s containing sulfone and imide linkages in the main chains (PAEKSI) were synthesized by electrophilic solution polycondensation of terephthaloyl chloride (TPC) with a mixture of DPE and BPBDADPS under mild conditions. The copolymers obtained were characterized by different physico-chemical techniques. The copolymers with 10–30 mol% BPBDADPS are semi-crystalline and had remarkably increased Tg values over commercially available PEEK and PEKK due to the incorporation of sulfone and imide linkages in the main chains. The copolymers III and IV with 20–30 mol% BPBDADPS had not only high Tg values of 180–187 °C, but also moderate Tm values of 338–341 °C, having good potential for the melt processing. The copolymers III and IV had tensile strengths of 100.7–104.2 MPa, Young’s moduli of 2.31–2.44 GPa, and elongations at break of 12.2–14.7% and exhibited high thermal stability and good resistance to organic solvents. [ABSTRACT FROM AUTHOR]

Poly(aryl ether ketone)s (PAEKs) are a class of high-performance engineering thermoplastics known for their excellent combination of chemical, physical and mechanical properties, and the synthesis of semicrystalline PAEKs with increased glass transition temperatures ( T) is of much interest. In the work reported, a series of novel copolymers of poly(ether ketone ketone) (PEKK) and poly(ether amide ether amide ether ketone ketone) were synthesized by electrophilic solution polycondensation of terephthaloyl chloride with a mixture of diphenyl ether and N, N′-bis(4-phenoxybenzoyl)-4,4′-diaminodiphenyl ether (BPBDAE) under mild conditions. The copolymers obtained were characterized using various physicochemical techniques. The copolymers with 10-35 mol% BPBDAE are semicrystalline and have markedly increased T over commercially available poly(ether ether ketone) and PEKK due to the incorporation of amide linkages in the main chain. The copolymers with 30-35 mol% BPBDAE not only have high T of 178-186 °C, but also moderate melting temperatures of 335-339 °C, having good potential for melt processing. The copolymers with 30-35 mol% BPBDAE have tensile strengths of 102.4-103.8 MPa, Young's moduli of 2.33-2.45 GPa and elongations at break of 11.7-13.2%, and exhibit high thermal stability and good resistance to organic solvents. Copyright © 2010 Society of Chemical Industry Poly(ether ketone ketone)/poly(ether amide ether amide ether ketone ketone) copolymers with high glass transition temperatures of 178-186 °C and moderate melting temperatures of 335-339 °C have been synthesized by electrophilic polycondensation of terephthaloyl chloride with a mixture of diphenyl ether and N, N′-bis(4-phenoxybenzoyl)-4,4′-diaminodiphenyl ether. [ABSTRACT FROM AUTHOR]

Abstract: Polymer blends based on sulfonated poly(ether ketone ketone) (SPEKK) as the proton-conducting component and poly(ether imide) (PEI) as the second component were considered for proton-exchange membranes (PEMs). The PEI was added to improve the mechanical stability and lower the water swelling in the fuel cell environment. Membranes were cast from solution using N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). The ternary, polymer/polymer/solvent, phase diagram was determined to provide guidance on how to control the morphology during solvent casting of blend membranes. For blends of SPEKK (ion-exchange capacity=2mequiv/g) with PEI as the minority component, the morphology consisted of dispersed particles of ∼0.5–6μm. Larger particles were achieved by increasing the PEI content and/or lowering the casting temperature. High-temperature annealing after solution casting did not affect the morphology of blend membranes, due to the low mobility and compatibility of the two polymers. The possible use of SPEKK/PEI blends in PEMs is discussed in terms of existing theories of ion transport in polymers. [Copyright &y& Elsevier]

Abstract: Poly(ether ketone ketone) was sulfonated using fumic sulfuric acid and used for preparation of proton conductive membranes. The sulfonation degree was evaluated by elemental and thermal analysis and the IEC values were determined by titration. The proton conductivity of membranes with sulfonation degrees up to 70% was determined as a function of temperature by impedance spectroscopy. Membranes with sulfonation degree 38–70% were tested in DMFC experiments. Their performance was comparable to Nafion® with the same pretreatment and clearly better than sulfonated poly(ether ether ketone) membranes with similar functionalization. The methanol crossover was lower than that of Nafion® in the same conditions. [Copyright &y& Elsevier]

Abstract: The importance of the blend microstructure and its effect on conductivity and structural integrity of proton exchange membranes (PEM) were investigated. Sulfonated poly(ether ketone ketone) (SPEKK) was selected as the proton-conducting component in a blend with either poly(ether sulfone) (PES) or SPEKK with a different sulfonation level. The second component was added to improve the mechanical stability in the fuel cell environment. Membranes were cast from solution using N-methyl-2-pyrrolidone (NMP) and dimethylacetamide (DMAc). Special attention was paid to the ternary solution behavior. Solution cast SPEKK/PES membranes are homogeneous for all studied compositions, 8/2 through 5/5 (w/w), and sulfonation levels, 1.7–3.5mequiv./g. Although this polymer pair does not show evidence for intrinsic compatibility, the excellent solvent quality results in a frozen-in structure during solution casting. The morphology of SPEKK/SPEKK blends can be tailor-made by finding the right balance between composition, casting solvent and temperature. Co-continuous morphologies can be devised for an SPEKK blend with sulfonation levels of 1.2 and 2mequiv./g. Both blends show lower swelling than the parent SPEKK. This results in better stability of PEMs during fuel cell testing. [Copyright &y& Elsevier]

Recent developments of the innovative LDF™ thermoplastic composites technology are reviewed with emphasis on discussion of the technology's fundamental basis and composites' property performance. The proprietary technology employs reinforce ment of long, aligned discontinuous fibers including carbon, Kevlar® or glass. Fabrication processes such as stretch forming and press forming can be employed in fabrication of LDF™ composite parts. The LDF™ composites technology is cost effective for manu facturing complex-shaped parts of aerospace structures. LDF™ composites show ex cellent mechanical properties comparable to that of the continuous fiber reinforced counterpart, since the reinforcing long fibers with thermoplastic matrix are well aligned. Mechanical test results with various LDF™ composites confirm the fundamental theory for non-continuous fiber reinforcement describing critical fiber length necessary to achieve efficient average stress transfer in a composite.The mechanical and other relevant property data are discussed for performance compar ison of LDF™ AS-4/PEKK or Kevlar®/PEKK composite material systems relative to the matched continuous fiber reinforced composites. Potential application of LDF™ ther moplastic composites technology for high performance aerospace structural parts are discussed with demonstration of thermoplastic wing ribs fabricated for V-22 tiltrotor air craft. [ABSTRACT FROM PUBLISHER]