Preparation and properties of poly(ether ether ketone) composites reinforced by modified wollastonite grafting with silaneterminated poly(ether ether ketone) oligomers

Silane-terminated poly(ether ether ketone) oligomers were synthesized and grafted onto wollastonite (W) particles. The prepared grafted-wollastonite particles (g-W) were then incorporated into PEEK matrix via melt processing. Properties of the PEEK composites were investigated using differential scanning calorimetry (DSC), universal tester and rheometer. The researchers found the mechanical properties of the PEEK/g-W composites were markedly enhanced, complex viscosity of the PEEK/g-W composites increased, and both the peak crystallization temperature (T _c ) and crystalline fraction (χ _c ) of the PEEK composites with g-W were significant higher compared with those of the PEEK composites with W. It is our belief that these results are due to the strong interaction between the grafted-wollastonite particles and the PEEK matrix.     

Interfacial shear strength in carbon fiber‐reinforced poly(phthalazinone ether ketone) composites

We studied interfacial shear strength (IFSS) in carbon fiber (CF)‐reinforced poly (phthalazinone ether ketone) (PPEK) composites system, with emphasis on the influence of forming temperature of composite and sizing agent on CFs. To obtain apparent IFSS of CF‐reinforced PPEK composites shaped at various forming temperatures ranged from 20 up to 370°C, microbond test was carried out at single‐fiber composites. Results of microbond test showed that apparent IFSS was directly proportional to the difference between the matrix solidification temperature (forming temperature) and the test temperature and approximately 80% of the apparent IFSS in CF/PPEK composite system was attributed to residual radial compressive stress at the fiber/matrix interface. By sizing CF with sizing agent, the wettability of the fiber by the matrix was improved and the final apparent IFSS was also improved. POLYM. COMPOS., 34:1921–1926, 2013. © 2013 Society of Plastics Engineers     

Synthesis and properties of novel copolymers of poly(ether ketone ether ketone ketone) and poly(ether ketone ketone ether ketone ketone) containing 1,4‐naphthylene moieties

A new monomer, 1,4‐bis(4‐phenoxybenzoyl)naphthalene (BPOBN), was conveniently synthesized via a simple synthetic procedure from readily available materials. A series of novel copolymers of poly(ether ketone ether ketone ketone) and poly(ether ketone ketone ether ketone ketone) containing 1,4‐naphthylene moieties were prepared by the Friedel‐Crafts acylation solution copolycondensation of terephthaloyl chloride (TPC) with a mixture of BPOBN and 4,4′‐diphenoxybenzophenone (DPOBPN), over a wide range of BPOBN/DPOBPN molar ratios, in the presence of anhydrous AlCl₃ and N‐methylpyrrolidone in 1,2‐dichloroethane. The copolymers with 10–40% BPOBN are semicrystalline and had remarkably increased T_gs over the conventional PEEK and PEKK due to the incorporation of 1,4‐naphthylene moieties in the main chains. The copolymers with 30–40 mol% BPOBN had not only high T_gs of 176–177°C, but also moderate T_ms of 332–338°C, which are suitable for the melt processing. These polymers had tensile strengths of 101.5–104.7 MPa, Young's moduli of 2.49–2.65 GPa, and elongations at break of 13.3–15.7% and exhibited high thermal stability and excellent resistance to organic solvents. POLYM. ENG. SCI., 56:566–572, 2016. © 2016 Society of Plastics Engineers     

Mechanical properties and sliding wear behavior of potassium titanate whiskers‐reinforced poly(ether ether ketone) composites under water‐lubricated condition

Polyetheretherketone (PEEK) composites reinforced with potassium titanate whiskers (PTW) were compounded using a twin‐screw extruder followed by injection molding. The effects of PTW on the mechanical properties, crystallization performances and wear behaviors of PEEK under water lubrication have been investigated. It was denoted that the yield strength, Young's modulus, and microhardness of the composites increased with increasing whisker content, but the elongation at break and the impact strength showed decreasing trend. It was revealed that the inclusion of PTW could effectively reduce the friction coefficient and enhance the wear resistance of the PEEK. The DSC tests showed that the crystallinity of the composite slightly decreased with the addition of PTW, which might imply that the crystallinity of PEEK was not the dominant factor that influenced the wear properties of the composites. The enhancement on the wear resistance was attributed to the reinforced effect of PTW on PEEK. The wear mechanism changed from fatigue wear into mild abrasive wear when the PTW was added into PEEK. The lowest wear rate 9.3 × 10^?8 mm³/Nm was achieved at 10 wt % PTW content. However, excessive whiskers would cause severe abrasive wear to the composite. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Properties and crystallization kinetics of poly(ether ether ketone)‐co‐poly(ether ether ketone ketone) block copolymers

A series of block copolymers composed of poly(ether ether ketone) (PEEK) and poly(ether ether ketone ketone) (PEEKK) components were prepared from their corresponding oligomers via a nucleophlilic aromatic substitution reaction. Various properties of the copolymers were investigated with differential scanning calorimetry (DSC) and a tensile testing machine. The results show that the copolymers exhibited no phase separation and that the relationship between the glass‐transition temperature (T_g) and the compositions of the copolymers approximately followed the formula T_g = T_g1X₁ + T_g2X₂, where T_g1 and T_g2 are the glass‐transition‐temperature values of PEEK and PEEKK, respectively, and X₁ and X₂ are the corresponding molar fractions of the PEEK and PEEKK segments in the copolymers, respectively. These copolymers showed good tensile properties. The crystallization kinetics of the copolymers were studied. The Avrami equation was used to describe the isothermal crystallization process. The nonisothermal crystallization was described by modified Avrami analysis by Jeziorny and by a combination of the Avrami and Ozawa equations. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1652–1658, 2005     

Thermal properties of melt‐blended poly(ether ether ketone) and poly(ether imide)

The thermal properties of blends of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) prepared by screw extrusion were investigated by differential scanning calorimetry. From the thermal analysis of amorphous PEEK–PEI blends which were obtained by quenching in liquid nitrogen, a single glass transition temperature (T_g) and negative excess heat capacities of mixing were observed with the blend composition. These results indicate that there is a favorable interaction between the PEEK and PEI in the blends and that there is miscibility between the two components. From the Lu and Weiss equation and a modified equation from this work, the polymer–polymer interaction parameter (χ₁₂) of the amorphous PEEK–PEI blends was calculated and found to range from −0.058 to −0.196 for the extruded blends with the compositions. The χ₁₂ values calculated from this work appear to be lower than the χ₁₂ values calculated from the Lu and Weiss equation. The χ₁₂ values calculated from the T_g method both ways decreased with increase of the PEI weight fraction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 733–739, 1999     

Effect of annealing on the properties of poly(ether ether ketone)

The effect of annealing on the properties of poly(ether ether ketone) has been studied by changing annealing temperature and time. Crystallinity increases with annealing temperature, but is little affected by annealing time. Annealing time results suggest an improved crystalline perfection as annealing time increases. Higher crystallinity levels cause an increase in stress-related properties and a decrease in strain-related properties. Crystalline perfection, however, seems to produce an increase in stress-related properties, but it does not affect strain-related properties. Consideration has also been given to the effect of other possible parameters different from crystalline structure, such as crosslinking, on the variation of properties.     

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

A novel monomer, bis[4‐(4‐fluorobenzoyl)phenyl]phenylphosphine oxide, was synthesized through the reaction of bis(4‐chloroformylphenyl) phenyl phosphine oxide with fluorobenzene. Three poly(ether ether ketone ketone)s derived from bis[4‐(4‐fluorobenzoyl)phenyl]phenylphosphine oxide and different aromatic bisphenols were prepared by aromatic nucleophilic substitution reactions. The resulting polymers had inherent viscosities in the range of 0.55–0.73 dL/g. The structures of the poly(ether ether ketone ketone)s were characterized with Fourier transform infrared and ¹H‐NMR. Thermal analysis indicated that the glass‐transition temperatures of the poly(ether ether ketone ketone)s were higher than 200°C, and the 5% weight loss temperatures in nitrogen were higher than 463°C. All the polymers showed excellent solubility in polar solvents such as N‐methyl‐2‐pyrrolidone, dimethylformamide, and dimethylacetamide and could also be dissolved in chlorinated methane. The polymers afforded transparent and flexible films by solvent casting. Organic phosphorous moieties also imparted good flame‐retardancy to the polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and properties of copolymers of poly(ether ketone ketone) and poly(ether amide ether amide ether ketone ketone)

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_g) 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_g 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_g 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     

Influence of the addition of lubricant on the properties of poly(ether ether ketone) fibers

A high‐temperature lubricant genioplast pellets (GPPS) was used in order to improve the processing behavior of poly(ether ether ketone) (PEEK) resin and high‐performance PEEK fibers were produced by melt‐spinning. The rheological properties of spinning material, morphology, mechanical, and thermal properties of PEEK fibers were characterized by using a polymer capillary rheometer, scanning electron microscopy, single fiber electronic tensile strength tester, wide‐angle X‐ray diffraction and thermal gravimetric analyzer, respectively. The results indicated that the introduction of lubricant GPPS decreased the melting viscosity of PEEK resin and improved spinnability of PEEK resin without sacrificing its thermal properties. The filaments are cylindrical with smooth surface and uniform diameter. The optimized content of GPPS was determined to be 1.0 wt% by balancing the decreased torque and changes of the mechanical properties. The strength and modulus of PEEK fibers were 420 MPa and 3.6 GPa, respectively. This should be due to the improvement in spinnability, followed by the enhancements in the orientation and crystallization of PEEK fibers in the process of drawing and annealing. POLYM. ENG. SCI., 53:2254–2260, 2013. © 2013 Society of Plastics Engineers     

Synthesis and properties of novel copolymers of poly(ether ketone diphenyl ketone ether ketone ketone) and poly(ether amide ether amide ether ketone ketone)

New monomers, 4,4′‐bis(4‐phenoxybenzoyl)diphenyl (BPOBDP) and N,N′‐bis(4‐phenoxybenzoyl)?4,4′‐diaminodiphenyl ether (BPBDAE), were conveniently synthesized via simple synthetic procedures from readily available materials. Novel copolymers of poly(ether ketone diphenyl ketone ether ketone ketone) (PEKDKEKK) and poly(ether amide ether amide ether ketone ketone) (PEAEAEKK) were synthesized by electrophilic Friedel‐Crafts solution copolycondensation of isophthaloyl chloride (IPC) with a mixture of BPOBDP and BPBDAE, over a wide range of BPOBDP/BPBDAE molar ratios, in the presence of anhydrous AlCl₃ and N‐methylpyrrolidone (NMP) in 1,2‐dichloroethane (DCE). The copolymers obtained were characterized by different physico‐chemical techniques. The copolymers with 10–40 mol% BPBDAE are semicrystalline and had remarkably increased T_gs over commercially available PEEK and PEKK due to the incorporation of amide and diphenyl linkages in the main chains. The copolymers IV and V with 30–40 mol% BPBDAE had not only high T_gs of 185–188°C, but also moderate T_ms of 326–330°C, having good potential for the melt processing. The copolymers IV and V had tensile strengths of 101.7–102.3 MPa, Young's moduli of 2.19–2.42 GPa, and elongations at break of 13.2–16.6% and exhibited high thermal stability and excellent resistance to organic solvents. POLYM. ENG. SCI., 54:1757–1764, 2014. © 2013 Society of Plastics Engineers     

Synthesis and properties of poly(ether ether ketone ketone)–poly(ether sulfone) block copolymers

Poly(ether ether ketone ketone)-poly(ether sulfone) (PEEKK/PES) block copolymers were prepared from the corresponding oligomers via a nucleophilic aromatic substitution reaction, and the M _n of the PEEKK segment was fixed at 12,000, while the M _n's of the PES segment ranged from 250 to 12,680. The different properties of the copolymers were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). The results showed that the relationship between T_g and compositions of copolymers approximately followed the formula 1/T_g = W₂/T_g2. The PES content and the segment length of the copolymers had a significant influence on their melting points and crystallization behavior. The thermal properties and dynamic mechanical behavior of the copolymers were also studied. In the study of isothermal crystallization, the copolymers have the same nucleation mechanism and crystal growth as that of pure PEEKK. Owing to the introduction of the PES segment into the PEEKK main chain, it increases the free energy which forms the critical crystal nucleus and produces a resistant action to the whole crystallization process of the PEEKK segment. © 1996 John Wiley & Sons, Inc.     

Improvement of interfacial properties of carbon fiber‐reinforced poly(phthalazinone ether ketone) composites by introducing carbon nanotube to the interphase

This article aims to improve interfacial properties of carbon fiber‐reinforced poly(phthalazinone ether ketone) (PPEK) composites by means of preparing carbon nanotube (CNT)/carbon fiber hybrid fiber. XPS was used to characterize the chemical structure of unsized carbon fiber and SEM was used to observe the surface topography of carbon fibers. Specific area measurement, dynamic contact angle, and interfacial shear strength (IFSS) testing were performed to examine the effect of CNT on the interfacial properties of carbon fiber/PPEK composites. By the introduction of CNT to the interphase of carbon fiber‐reinforced PPEK composites, an enhancement of IFSS by 55.52% was achieved. Meanwhile, the interfacial fracture topography was also observed and the reinforcing mechanism was discussed. POLYM. COMPOS., 36:26–33, 2015. © 2014 Society of Plastics Engineers     

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

A 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 (T_g) and melting temperature (T_m) 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     

Effect of thermotropic liquid crystalline poly(ether ketone)arylates on the processibility and properties of poly(ether ether ketone)s fibers

A series of composite fibers based on poly(ether ether ketone)s (PEEK) and a thermotropic liquid crystalline poly(ether ketone)arylates (PEKAR) have been prepared by melt spinning. The structure, compatibility, and properties of these composite fibers were investigated in detail by rheological measurements, differential scanning calorimetry, thermogravimetric analysis, wide‐angle X‐ray diffraction, scanning electron microscopy, orientation degree test, and mechanical properties test. The results showed that the addition of PEKAR could reduce the apparent melt viscosity of the blends obviously, which is beneficial in improving the processibility of PEEK at a relatively low temperature. After adding 1 wt % PEKAR to PEEK, the tensile strength of the post‐treatment fiber improved by 8.8%, whereas the crystallinity of the as‐spun fiber increased from 21.76% to 31.51%, and the orientation degree also increased with the addition of PEKAR. The result of morphology research suggested that PEKAR had a good compatibility with PEEK resin. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40595.     

Effect of dihydroxydiphenyl ether on poly(ether ether ketone)

A series of modified poly(ether ether ketone) (PEEK) polymers were synthesized by introduction of addition ether groups from dihydroxydiphenyl ether (DHDE) into the PEEK structure. The inherent viscosity of the DHDE-modified PEEK increased with reaction time at 320 °C. DSC thermograms showed the melting points of the obtained PEEK decreased with the increase of the DHDE content in the backbone. The degradation temperature (T_d) was slightly decreased by the introduction of DHDE. The crystallinity as measured via the X-ray diffraction (XRD) increases with the introduction of DHDE into the modified PEEK. The crystalline structure was identified as an orthorhombic structure with lattice constants a = 7.72 Å, b = 5.86 Å, and c = 10.24 Å. Due to the glass transition temperature (T_g) and the melting temperature (T_m) decreasing with the increase of the DHDE content in the reaction system. the processability of the resultant PEEK could be improved through this DHDE modification.     

Functionalization of multi‐walled carbon nanotubes and their effect on the tribological properties of poly(ether ether ketone) composites

A series of copolymers containing conjugated fluorene groups as a compatibilizer to improve the dispersion of multi‐walled carbon nanotubes (MWCNTs) were prepared and used to improve the wear resistance of poly(ether ether ketone)/graphite (PEEK/GP) composites. The solubility of MWCNTs had a maximum at a concentration ratio of 2:1 polymer:MWCNTs. Transmission electron microscopy indicated that polymer ? MWCNT interactions were capable of partially debundling the nanotubes in chloroform, with individual nanotubes or small bundles clearly observed. The tribological properties of PEEK composites incorporating the modified MWCNTs were investigated using a pin‐on‐disc apparatus and a block‐on‐ring apparatus. The PEEK composites had a lower frictional coefficient under the block‐on‐ring testing condition, but a lower wear rate was achieved in the pin‐on‐disc test. © 2017 Society of Chemical Industry     

Isothermal crystallization and melting behavior of short carbon fiber reinforced poly(ether ether ketone) composites

Films of short carbon fiber reinforced poly(ether ether ketone) (PEEK) composite were formed by compression molding pellets for 10 min at 380 °C under air. A heating stage was used to prepare isothermally treated PEEK composites before DSC scan. The dependence of degree of crystallinity on the heating rate (10–80 °C/min) was investigated for specimens crystallized at different temperatures. The results indicated that 50 °C/min was an optimum heating rate to suppress the reorganization and to avoid the superheating of high crystallinity specimens with the sample weight of 10 mg. The upper peak temperature of double-melting peaks continued to increase with crystallization temperature. This peak temperature was related to the transition from regime II to III. The phenomenon of lower crystallinity and higher melting temperature supports the interpretation that the upper melting peak corresponded to crystals growing during the earlier stage of isothermal crystallization.     

Modified continuous carbon fiber‐reinforced poly(phthalazinone ether sulfone ketone) composites by blending polyetherimide and polyethersulfone

Poly(phthalazinone ether sulfone ketone) (PPESK) is a novel high performance thermoplastic with outstanding high temperature resistance and excellent mechanical properties and therefore, it is a very ideal candidate matrix for advanced composites. However, its high melting viscosity makes the melting process difficult. In this article, two well‐known high performance thermoplastics, polyetherimide (PEI) and polyethersulfone (PES) were introduced to PPESK in order to reduce the melting viscosity of PPESK and to improve the properties of composites. The effect of addition of PEI and PES on the resultant composites was studied. A series of unidirectional composites were made of PPESK and its PEI and PES blends as matrix and continuous carbon fiber (T700) as reinforcement. The solution prepregging method and hot‐press molding method were used in preparation of composites. The effects of polymer blends matrix on mechanical properties, interfacial adhesion, and fracture mode were studied by three points bending, interlaminar shearing, porosity, and scanning electron microscope test. The results show that the mechanical properties and interfacial adhesion increases, and the porosity decrease after blending PEI or PES in the matrix. Addition of PEI and PES to PPESK results in an obvious transition of fracture mode. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Rheological properties of phenophthalein poly(ether ether ketone)

The rheological properties of the novel engineering thermoplastic phenophthalein poly(ether ether ketone) (PEK-C) have been investigated using both a rotational and a capillary rheometer. The dependence of the viscosity on the shear rate and temperature was obtained. The activation energy was evaluated both from the Arrhenius and the Williams-Landel-Ferry (WLF) equation. An estimate for the proper E_η (dependent only on the chemical structure of the polymer) has been found from the WLF equation at temperatures about T_g + 200°C. Measurements of the die swell have been performed. The first normal stress differences were evaluated from the die swell results and compared with the values obtained from the rotational rheometer at low shear rates.