High performance PEEK/carbon nanotube composites compatibilized with polysulfones-II. Mechanical and electrical properties

The mechanical and electrical properties of poly(ether ether ketone) (PEEK)/single-walled carbon nanotube (SWCNT) composites with polysulfones as compatibilizers have been analyzed. Dynamic mechanical studies reveal that these composites exhibit considerably higher storage modulus and glass transition temperature than non-compatibilized samples. Tensile tests indicate a non-linear growth in the Young’s modulus and strength with increasing SWCNT loading, related to changes in the degree of crystallinity of the composites. The moduli of samples with very low CNT content exceed the predictions by the rule of mixtures, whilst at higher concentrations fall slightly below the theoretical values. The addition of the polysulfones increases the stiffness and toughness of the composites, attributed to an improved filler dispersion and stronger matrix-reinforcement interfacial adhesion. Fractography analyses suggest that these compatibilizers favor the ductile deformation of the matrix. The electrical and thermal conductivities of the composites decrease slightly in the presence of the polysulfones, albeit are well above the values of pure PEEK. Enhanced properties are found for samples including wrapped laser-grown SWCNTs. The overall mechanical performance of the compatibilized composites is suitable for use in lightweight structural applications, particularly for the aeronautic industry.     

High performance PEEK/carbon nanotube composites compatibilized with polysulfones-I. Structure and thermal properties

Poly(ether ether ketone) (PEEK)/single-walled carbon nanotube (SWCNT) composites incorporating polysulfones as compatibilizers were fabricated by melt-blending, after pre-processing based on ball milling and mechanical treatments in an organic solvent. Their structure, morphology and thermal properties have been investigated. Microscopic observations showed a uniform distribution of the CNTs and good miscibility between the compatibilizer and matrix phases. The incorporation of wrapped SWCNTs leads to a remarkable increase in the degradation temperatures of the matrix in comparison with non-compatibilized samples, attributed to the high thermal stability of the polysulfones and the compatibilizing effect. The addition of very small CNT loadings raises the crystallization temperature and the degree of crystallinity of PEEK. At higher concentrations, the inactive nucleating activity of the nanofillers, the confinement of the polymer chains within the CNT network and the presence of an amorphous compatibilizer moderately hinder PEEK crystallization. Synchrotron X-ray diffraction experiments indicate the existence of reorganization phenomena of the matrix crystals during the heating of the composites. Improved thermal properties are found for composites incorporating arc-purified SWCNTs, attributed to the higher degree of debundling and lower metal content of these CNTs. These compatibilized composites are new materials for potential high-temperature structural applications.     

Development and characterization of PEEK/carbon nanotube composites

New poly(ether ether ketone) (PEEK) based composites have been fabricated by the incorporation of single-walled carbon nanotubes (SWCNTs) using melt processing. Their structure, morphology, thermal and mechanical properties have been investigated. Scanning electron microscopy observations demonstrated a more uniform distribution of the CNTs for samples prepared following a processing route based on polymer ball milling and CNT dispersion in ethanol media. Thermogravimetric analysis indicated a remarkable improvement in the thermal stability of the matrix by the incorporation of SWCNTs. Differential scanning calorimetry showed a decrease in the crystallization temperature with increasing SWCNT content, whilst no significant changes were observed in the melting of the composites. The crystallite size determined by X-ray diffraction decreased at high SWCNT loading, which is attributed to the spatial limitations on crystal growth by confinement within the CNT network. Dynamic mechanical analysis revealed an increase in the storage moduli, hence in the rigidity of the systems, with increasing SWCNT content. Their addition shifts the glass transition peak to higher temperatures due to the restriction in chain mobility imposed by the CNTs. Higher thermal stability and mechanical strength were found for composites with improved dispersion of the SWCNTs.     

Enhanced mechanical and electrical properties of carbon fiber/poly(ether ether ketone) laminates via inserting carbon nanotubes interleaves

The carbon fiber/(carbon nanotubes/polyetherimide)/poly ether ether ketone (CF/(CNTs/PEI)/PEEK) laminates are prepared by inserting carbon nanotubes/polyetherimide (CNTs/PEI) interleaves into interlaminar region. The mechanical properties and electrical conductivities of the developed laminates are evaluated. The results indicate that the interlaminar shear strength and flexural strength of CF/(CNTs/PEI)/PEEK laminates are increased by 42.9% and 24.7%, after inserting CNTs2.91/PEI interleaves, respectively. The cross-sectional images of laminates after mechanical tests verify strong fiber-resin adhesion by scanning electron microscope observation. The pertinent mechanism responsible for the improvement of mechanical properties is mechanical interlocking effect of CNTs. After incorporating CNTs/PEI interleaves, the electrical conductivity of laminates is markedly improved due to the formation of conductive pathway. This work suggests that this method is compatible with the preparation process of thermoplastic composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48658.     

Hybrid fiber fabric composites from poly ether ether ketone and glass fiber

Poly ether ether ketone (PEEK) polymer was extruded into filaments and cowoven into unidirectional hybrid fabric with glass as reinforcement fiber. The hybrid fabrics were then converted into laminates and their properties with special reference to crystallization behavior has been studied. The composite laminates have been evaluated for mechanical properties, such as tensile strength, interlaminar shear strength (ILSS), and flexural strength. The thermal behavior of the composite laminates were analyzed using differential scanning calorimeter, thermogravimetric analyzer, dynamic mechanical analyzer (DMA), and thermomechanical analyzer (TMA). The exposure of the fabricated composite laminates to high temperature (400 and 500°C) using radiant heat source resulted in an improvement in the crystallanity. The morphological behavior and PEEK resin distribution in the composite laminates were confirmed using scanning electron microscope (SEM) and nondestructive testing (NDT). Although DMA results showed a loss in modulus above glass transition temperature (T_g), a fair retention in properties was noticed up to 300°C. The ability of the composite laminates to undergo positive thermal expansion as confirmed through TMA suggests the potential application of glass–PEEK composites in aerospace sector. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117:1446–1459, 2010     

Poly(ether ether ketone)/wrapped graphite nanosheets with poly(ether sulfone) composites: Preparation,mechanical properties,and tribological behavior

Antiwear composites with extraordinary tribological performances and good mechanical/thermal properties were developed by the dispersion of poly(ether sulfone) (PES) wrapped graphite nanosheets (GNSs) inside a poly(ether ether ketone) (PEEK) matrix via melt blending. The tribological behaviors and the mechanical/thermal properties of the composites were carefully investigated. Compared with pure PEEK and PEEK/GNS composites, the PEEK/wrapped GNS composites exhibited considerable enhancements in those performances; these were attributed to the eliminated layer of PES; this elimination not only eliminated the GNS aggregation inside the PEEK matrix for homogeneous distribution inside the PEEK matrix but also enhanced the interfacial adhesion between the PEEK and wrapped GNSs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41728.     

A comparative study on the influences of whisker and conventional carbon nanotubes on the electrical and thermal conductivity of polyether ether ketone composites

In this study, the electrical and thermal conductivity of polyether ether ketone (PEEK)/carbon nanotubes (CNTs) with different types, namely whisker CNTs (Wh-CNTs) and conventional CNTs were compared. PEEK/CNTs composites were melt mixed in PEEK via two screw extrusion technology. Moreover, the effects of different methods for mixing of PEEK/Wh-CNTs, namely, dry mixing, wet mixing and melt mixing, were compared. The electrical and thermal properties were analyzed. A high thermal conductivity value of about 0.741 W/(m K) could be obtained upon loading with 10 wt% Wh-CNTs and the PEEK/Wh-CNTs composites had low volume resistivity value of 10.96 Ω cm at 10 wt% loading via melt mixing. Thermal conductivity values of 1.066 W/(m K) (out-of-plane) and 1.50 W/(m K) (in-plane) were achieved with 10 wt% loading by wet mixing. Experimental results of out-of-plane thermal conductivity were more consistent with the Nan model. PEEK/Wh-CNTs composites prepared by wet mixing exhibited higher thermal conductivity than the composites mixed using the two other methods. As the content of Wh-CNTs in wet mixed PEEK/Wh-CNTs nanocomposites increased, electromagnetic interference (EMI) shielding effectiveness (SE) was improved. The PEEK/Wh-CNTs composites were 0.6 mm thick and showed an EMI SE of 21.5 dB.     

碳纤维增强聚醚醚酮复合材料的制备工艺及耐磨和导电性研究

介绍了碳纤维增强聚醚醚酮(PEEK)复合材料制备工艺、机械力学性能、摩擦磨损机理、导电性,重点研究了制备工艺对机械力学性能的影响,碳纤维添加量和碳纤维的表面处理,对耐磨性和导电性的影响。通过SEM照片和DSC曲线以证明:PEEK和碳纤维结有着良好的结合性,这对复合材料导电性和耐磨性产生一定影响,即随着碳纤维质量分数增加导电性和耐磨性都有提高,碳纤维表面处理有利于提高耐磨性。     

Study on poly(ether ether ketone)/organically modified montmorillonite composites

Abstract

Novel poly(ether ether ketone) (PEEK)/organically modified montmorillonite (OMMT) composites containing 0–10 wt-% fractions of OMMT were prepared by melting blending method and the microstructure, thermal and mechanical properties were investigated using different characterisation techniques. X-ray diffraction and transmission electron microscopy showed that the OMMT was well dispersed with microscale in the PEEK matrix. Differential scanning calorimetry indicated that the glass transition temperature T _g and melt temperature T _m of PEEK/OMMT composites (POMCs) were hardly affected by the addition of OMMT, while the crystal temperature T _c decreased when the amount of OMMT excessed 1 wt-%. The data of thermogravimetric analysis exhibited that the thermal stability of POMCs in higher temperature region was better than that of pure PEEK. The results of mechanical properties test revealed that modulus and strength of POMCs increased with the content of OMMT, whereas the elongation at break and impact strength of POMCs decreased.     

Poly(ether ether ketone) composites reinforced by short carbon fibers and zirconium dioxide nanoparticles: Mechanical properties and sliding wear behavior with water lubrication

Poly(ether ether ketone) (PEEK) composites reinforced by short carbon fibers (SCFs) and nanoscale zirconium dioxide (ZrO₂) particles were prepared by twin‐screw extrusion compounding and subsequently injection molding. The effects of SCFs and ZrO₂ nanoparticles on the mechanical properties and wear behavior of PEEK composites with water lubrication were investigated. The mechanical properties of the composites were dramatically enhanced by the incorporation of SCFs. The addition of nano‐ZrO₂ also promoted efficient improvements in the stiffness and hardness but degraded the impact strength. The compounding of the two fillers remarkably improved the wear resistance of the composites under aqueous conditions and especially under high pressures. The excellent wear resistance of the PEEK/carbon fiber (CF)/ZrO₂ composites under aqueous conditions was revealed to be due to a synergy effect between the ZrO₂ nanoparticles and CFs. The SCFs carried the majority of the load during a sliding process and prevented severe wear of the matrix. The incorporation of nano‐ZrO₂ efficiently inhibited CF failure by reducing the stress concentration on the CF interface and the shear stress between two sliding surfaces via a positive rolling effect of the nanoparticles. Furthermore, a linear correlation was found between the wear rate and some mechanical properties of the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetics of strain-induced crystallization during injection molding of short fiber composites of poly(ether ether ketone)

Crystallization kinetics of short glass and carbon fiber composites of poly(ether ether ketone) (PEEK) under melt-strain conditions have been obtained for the first time, using in-situ wide angle X-ray scattering, and have been correlated to a model based on the Avrami equation in order to enable minimization of the processing time for injection molding of these materials. It has been demonstrated that increased flow rate of the melt in the mold and, consequently, increased shear rate accelerates the crystallization process of PEEK composites, analogous to similar trends observed previously in PEEK resin. Short glass fiber composites of PEEK crystallize slower than the resin under identical processing conditions, while short carbon fiber composites crystallize faster than the resin, except at the highest mold temperatures and the lowest flow rates. A model based on the Avrami equation has been proposed to fit the kinetics data obtained experimentally. The Avrami coefficient has been calculated and Arrhenius plots have been used to predict the crystallization kinetics at temperatures lower than those at which experimental data have been obtained here. Fiber orientation, flexural elastic modulus, and flexural fracture toughness of the composites have also been evaluated.     

Fabrication of High Thermally Conductive and Electrical Insulating Composites by Boron Nitride-Nanosheet-Coated PEEK Fiber

The development of polyether ether ketone (PEEK)-based thermally conductive insulating composites is required in miniaturized electronic devices with a high power density where heat needs to be evacuated. However, the low thermal conductivity (TC) remains a great challenge, significantly restricting the large-scale applications of PEEK. Here, a novel class of boron nitride nanosheets (BNNSs)/PEEK composites with excellent heat dissipation properties through BNNS-coated PEEK fiber is developed, through simple hot-press sintering. A direct comparison of experimental measurements between the BNNSs/PEEK fiber composites and the BNNSs/PEEK powder composites indicates that the TC is greatly improved in the presence of the well-orientated structure of BNNSs. In addition, the composite with high loading of BNNSs exhibits a combination of high tensile strength and significant electrical insulation (volume electrical resistivity beyond 10⁹ Ω cm). The experimental data demonstrate that it has broad and bright prospects for application in a range of emerging electronic devices, which also provide great potential for enhancing the thermal management application of PEEK-based composites.     

Cellular structures of carbon nanotubes in a polymer matrix improve properties relative to composites with dispersed nanotubes

A new processing method has been developed to combine a polymer and single wall carbon nanotubes (SWCNTs) to form electrically conductive composites with desirable rheological and mechanical properties. The process involves coating polystyrene (PS) pellets with SWCNTs and then hot pressing to make a contiguous, cellular SWCNT structure. By this method, the electrical percolation threshold decreases and the electrical conductivity increases significantly as compared to composites with well-dispersed SWCNTs. For example, a SWCNT/PS composite with 0.5 wt% nanotubes made by this coated particle process (CPP) has an electrical conductivity of ∼3 × 10⁻⁴ S/cm, while a well-dispersed composite made by a coagulation method with the same SWCNT amount has an electrical conductivity of only ∼10⁻⁸ S/cm. The rheological properties of the composite with a macroscopic cellular SWCNT structure are comparable to PS, while the well-dispersed composite exhibits a solid-like behavior, indicating that the composites made by this new CPP are more processable. In addition, the mechanical properties of the CPP-made composite decrease only slightly, as compared with PS. Relative to the common approach of seeking better dispersion, this new fabrication method provides an important alternative means to higher electrical conductivity in SWCNT/polymer composites. Our straightforward particle coating and pressing method avoids organic solvents and is suitable for large-scale, inexpensive processing using a wide variety of polymers and nanoparticles.     

Processing,microstructure, and failure behavior in short-fiber-reinforced poly(ether ether ketone) composites

Short-fiber-reinforced poly(ether ether ketone) (PEEK) composites were prepared by a specially designed mold. Both compression- and extrusion-molded plaques were obtained under the same thermal history. The fiber length distribution, fiber volume fraction, and fiber orientation are characterized. The fibers show an in-plane random orientation in compression-molded plaques, but they exhibit a 3-layer fiber orientation well-known for injection moldings in extrusion-molded composites. It is the final aim to simulate the rheological and morphologic behavior in injection moldings by using the laboratory designed extrusion/compression mold. Static compact tension (CT) specimens and electron microscopy (EM) were used to investigate the failure behavior. Results showed that crack initiation is the dominant failure energy absorption process in a brittle fracture, whereas crack propagation is dominant in a ductile failure. The extruded composites were mechanically characterized in two orthogonal directions (T- and L-type). The anisotropy factor is reported as 1.2.     

Enhanced electrical properties by tuning the phase morphology of multiwalled carbon nanotube‐filled poly(ether ether ketone)/polyimide composites

A novel high‐performance material with enhanced electrical properties was obtained by tuning the phase morphology of poly(ether ether ketone) (PEEK)/thermoplastic polyimide (TPI)/multiwalled carbon nanotube (MWCNT) composites. MWCNTs were selectively located in the TPI phase due to discrepant affinity of MWCNTs between PEEK and TPI. The dependence of the electrical properties of the PEEK/TPI/MWCNT composites on the phase morphology was investigated by changing the PEEK/TPI ratio, and the maximum conductivity was achieved with a PEEK/TPI ratio of 50/50, which could be explained by the selective location of MWCNTs and the co‐continuous phase morphology of the composites. © 2015 Society of Chemical Industry     

Effect of the addition of silane coupling agents on the properties of wollastonite‐reinforced poly(ether ether ketone) composites

The wollastonite was grafted with different silane coupling agents, which could improve interface adhesion. Wollastonite and modified wollastonite‐reinforced poly(ether ether ketone) (PEEK) composites were prepared by melt blending. The mechanical properties, rheology behavior, and thermal properties of the composites were investigated. The modified wollastonite‐reinforced PEEK composites exhibited better mechanical properties than the unmodified wollastonite‐reinforced PEEK composites based on good interfacial adhesion. The composites had lower activation volume and complex shear viscosity. Furthermore, the modified wollastonite‐reinforced PEEK composites had higher crystallization peak temperature (T_c) and crystalline fraction (χ_c) compared with the unmodified wollastonite‐reinforced PEEK composites. This study shows that the traditional silane coupling agents could effectively improve the performance of PEEK composites. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

The influence of single-walled carbon nanotube functionalization on the electronic properties of their polyaniline composites

The “in situ” preparation and characterization of composites of polyaniline (PANI) and single-walled carbon nanotubes (SWCNTs) are reported. To improve the dispersion and compatibility with the polymer matrix the raw SWCNTs were modified following different routes. SWCNTs oxidized by chemical or thermal treatments (nitric acid and air oxidation, respectively) were subjected to covalent functionalization with octadecylamine (ODA). SWCNT/PANI composites were prepared either from just oxidized SWCNTs, or from ODA functionalized SWCNTs. Temperature-programmed desorption, elemental analyses, ultraviolet-visible (UV-vis), UV-vis with near infrared and Raman spectroscopy, X-ray diffraction, scanning and transmission electron microscopy and conductivity measurements were used to characterize the functionalized SWCNT materials, dispersions and composites. The PANI composite prepared from air oxidized SWCNTs showed the best electrical conductivity indicating a better interaction with polyaniline than ODA functionalised SWCNTs. The improvement of conductivity is attributed to the doping effect or charge transfer of quinoide rings from PANI to SWCNTs.     

玻璃纤维增强PEEK复合材料的高速干摩擦性能

利用球盘式摩擦磨损试验机对质量分数为30%的短切玻璃纤维增强聚醚醚酮(PEEK/GF)复合材料进行室温高速条件下干滑动磨损实验,考察了载荷及频率对材料摩擦系数及磨损量的影响,并对摩擦前后的微观形貌及热性能进行了分析。结果表明,随着载荷和频率的增加,PEEK/GF复合材料的摩擦系数和磨损量逐渐增大并趋于稳定;微观结构分析显示GF与PEEK两相结合紧密,磨损方式主要以犁沟为主,GF的加入阻断了PEEK从PEEK/GF复合材料磨损表面剥落,使PEEK磨屑在GF周围积聚,摩擦表面产生的热量使PEEK收缩团聚在一起;PEEK/GF复合材料的热分解温度比纯PEEK提高了75℃。     

High performance thermoplastic composites: Study on the mechanical,thermal, and electrical resistivity properties of carbon fiber‐reinforced polyetheretherketone and polyethersulphone

High temperature processing thermoplastic polymers, polyetheretherketone (PEEK) and polyethersulphone (PES), were melt blended with carbon fibers (CFs) to make composites. These composites were investigated for their mechanical, thermal, and electrical properties. Mechanical properties that are expressed in terms of storage modulus, loss, and damping were enhanced with the addition of CFs. Thermal properties were determined by DSC and TGA. These methods help to understand the effects of fiber content and fiber–matrix adhesion in the composites. Composites were also tested for their electrical and thermal conductivity because CFs leave the composites thermally and electrically conductive. CFs enhanced the crystallinity of the PEEK appreciably that in turn influenced thermal conductivity, electrical resistivity, and the stiffness of PEEK/CF (composites of PEEK with CFs). PES/CF (composites of PES with CF) shows a different behavior due to the amorphous nature of PES. The work involves one filler and two different matrices, and so it provides an interesting comparison of how matrix morphology can influence the properties of composites. POLYM. COMPOS. 28:785–796, 2007. © 2007 Society of Plastics Engineers.     

Simultaneous enhancements in the mechanical,thermal, and electrical performances of glass‐fiber‐reinforced cyanate ester/epoxy composites with plasma‐functionalized carbon nanotubes at different temperatures

Woven glass‐fiber‐reinforced cyanate ester/epoxy composites modified with plasma‐functionalized multiwalled carbon nanotubes (MWCNTs) were prepared. The mechanical, thermal, and electrical properties of the composites were investigated at different temperatures. The results show that the interlaminar shear strength, thermal conductivity, and electrical conductivity of the composites at room temperature and the cryogenic temperatures were enhanced simultaneously by the incorporation of MWCNTs, whereas the nonconductive behavior of the composites as electrical insulating materials was not changed. Meanwhile, the reinforcing mechanism was also examined on the basis of the microstructure of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41418.