Synthesis of glass fiber‐multiwall carbon nanotube hybrid structures for high‐performance conductive composites

The conductive polyamide 66 (PA66)/carbon nanotube (CNT) composites reinforced with glass fiber‐multiwall CNT (GF‐MWCNT) hybrids were prepared by melt mixing. Electrostactic adsorption was utilized for the deposition of MWCNTs on the surfaces of glass fibers (GFs) to construct hybrid reinforcement with high‐electrical conductivity. The fabricated PA66/CNT composites reinforced with GF‐MWCNT hybrids showed enhanced electrical conductivity and mechanical properties as compared to those of PA66/CNT or PA66/GF/CNT composites. A significant reduction in percolation threshold was found for PA66/GF‐MWCNT/CNT composite (only 0.70 vol%). The morphological investigation demonstrated that MWCNT coating on the surfaces of the GFs improved load transfer between the GFs and the matrix. The presence of MWCNTs in the matrix‐rich interfacial regions enhanced the tensile modulus of the composite by about 10% than that of PA66/GF/CNT composite at the same CNT loading, which shows a promising route to build up high‐performance conductive composites. POLYM. COMPOS. 34:1313–1320, 2013. © 2013 Society of Plastics Engineers     

Rheological properties and fracture toughness of epoxy resin/multi‐walled carbon nanotube composites

Multi‐walled carbon nanotubes (MWCNTs), surface‐treated via chemical functionalization, i.e., oxidation and amidation, were used to reinforce diglycidylether of bisphenol F (DGEBF) epoxy resin. The effects of the functionalization on the dispersion stability, rheological properties, and fracture toughness of DGEBF/MWCNT composites were investigated. The dispersion homogeneity of the MWCNTs in the epoxy matrix improved after functionalization. In addition, isothermal rheology measurements revealed that the DGEBF/dodecyl amine‐functionalized MWCNT (D‐MWCNT) composite had a longer gel time and higher activation energy of cross‐linking than the DGEBF/acid‐treated MWCNT (A‐MWCNT) composite. The fracture toughness of the former was also significantly higher than that of the latter; this resulted from the relatively high dispersion stability of the D‐MWCNTs in the epoxy matrix, owing to the presence of alkyl groups on the D‐MWCNT surface. POLYM. ENG. SCI., 55:2676–2682, 2015. © 2015 Society of Plastics Engineers     

Graphite fluoride and fluorographene as a new class of solid lubricant additives for high‐performance polyamide 66 composites with excellent mechanical and tribological properties

Fluorographene (FG) with layer numbers of 3–4 was successfully prepared through facile microwave‐assisted liquid phase exfoliation of raw graphite fluoride (GrF). The raw GrF and the as‐prepared FG were then directly incorporated into polyamide 66 (PA66) by melt processing without using any surfactants. Microstructural, mechanical and tribological properties of the prepared PA66 composites were investigated. Various characterization results showed that both GrF and FG, as novel solid lubricants, can effectively improve the mechanical and anti‐wear performances of the PA66 matrix. It was also found that FG is better at improving mechanical properties and reducing the friction of PA66 than GrF at low concentrations owing to the large surface–volume ratio. The addition of 0.5 wt% FG into PA66 exhibits a ca 13% increase in tensile modulus, ca 5% increase in tensile strength, ca 18% reduction in coefficient of friction (COF) and ca 43% reduction in wear rate. However, at relatively high concentrations, such as 1.0 wt%, GrF shows a better reinforcement effect than FG owing to a uniform dispersion of GrF in the PA66 matrix. The addition of 1.0 wt% GrF into PA66 exhibits a ca 18% increase in tensile modulus, ca 5% increase in tensile strength, ca 37% reduction in COF and ca 46% reduction in wear rate. Wear tests also show that the excellent wear resistance of the PA66 composites is due to the improved mechanical properties and the lubrication of GrF and FG between the worn surfaces. Our current work demonstrates the tremendous potentials of fluorinated carbon materials for enhancing mechanical and anti‐wear properties of polymeric materials. © 2020 Society of Chemical Industry     

Properties of surface‐modified multiwalled carbon nanotube filled poly(ethylene terephthalate) composite films

Poly(ethylene terephthalate) (PET)/multiwalled carbon nanotube (MWCNT) composites were prepared by in situ polymerization. To improve the dispersion of MWCNTs in the PET matrix, functionalized MWCNTs having acid groups (acid‐MWCNTs) and acetic groups (acetic‐MWCNTs) on their surfaces were used. The functional groups were confirmed by infrared spectrometry. Scanning electron microscopy showed that acetic‐MWCNTs had a better dispersion in the PET matrix than pristine MWCNTs and acid‐MWCNTs. A reaction between PET and acetic‐MWCNTs was confirmed by a shift of the Raman G band to a higher frequency and an increase of the complex viscosity in the rheological properties. The composites containing functionalized MWCNTs showed a large increase in their tensile strengths and moduli. The values of the strengths and moduli of the PET/acetic‐MWCNT composites were higher than those of the PET/acid‐MWCNT composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Toward improved mechanical performance of multiscale carbon fiber and carbon nanotube epoxy composites

A novel class of multiscale epoxy composites was developed containing carbon fibers (CFs) and multiwalled carbon nanotubes (MWCNTs) to explore their mutual effect on the mechanical performance of composites. The loading of CFs in composites was kept constant at ∼60 wt%, while the contents of MWCNTs were increased from 0.5 to 2.0 wt%. MWCNTs were functionalized through acid treatment before incorporating into epoxy matrix to promote dispersion quality. The developed composites were characterized microstructurally by scanning electron microscopy and mechanically by tensile, flexural, edgewise compression, and hardness tests. Homogeneous dispersion of MWCNTs was observed until their loading of 1.5 wt%, which enhanced the mechanical performance of composites. Hardness increased up to 47% while tensile, flexural, and edgewise compressive moduli increased to 40%, 16.3%, and 164%, respectively. Moreover, tensile, flexural, and edgewise compressive strengths showed rises of 45%, 15.2%, and 43%, respectively. The fracture strain increased in both the tensile and flexural tests while it decreased in edgewise compressive tests. Increasing the MWCNTs in composites to 2.0 wt% produced their agglomerates and reversed the rising trend in mechanical properties. POLYM. COMPOS., 38:1519–1528, 2017. © 2015 Society of Plastics Engineers     

l-Phenylalanine amino acid functionalized multi walled carbon nanotube (MWCNT) as a reinforced filler for improving mechanical and morphological properties of poly(vinyl alcohol)/MWCNT composite

Carbon nanotube dispersion in polymer matrix is one of the most crucially important aspects in carbon nanotube/polymer composites. This paper is aimed to discuss the considerable improvement in dispersion of multi walled carbon nanotubes (MWNTs) in poly(vinyl alcohol) (PVA) matrix that was attained through bio-functionalization of MWCNTs. Initially, for getting better dispersion in water, pure MWCNTs have been functionalized by l-phenylalanine amino acid. The functionalized MWCNTs (f-MWCNTs) show much enhanced solubility in water. So, effects of modified MWCNT on dispersion in PVA matrix and certain properties of the resulting composites, like; mechanical, thermal and morphological properties were studied. The prepared composites were examined by Fourier transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. Also, the mechanical and thermal properties of composite films have been investigated and revealed that incorporation of just a few percent of f-MWCNTs can improve the PVA mechanical and thermal properties significantly.     

Hydrogen bond containing multiwalled carbon nanotubes in polyurethane composites

Introduction of hydrogen bonding sites onto multi‐walled carbon nanotubes (MWCNTs) included carboxylic acid, amide‐amine, and novel amide‐urea MWCNTs for the formation of homogenous polyurethane composites. Acid oxidation and subsequent derivatization introduced hydrogen bonding functionality onto MWCNTs to reveal the effect of surface functionalization on mechanical properties in a 45 wt% hard segment polyurethane matrix. Raman spectroscopy showed an increase in the D/G peak ratio, which indicated successful oxidation, and X‐ray photoelectron spectroscopy also revealed elemental compositions that supported each step of the functionalization strategy. Thermogravimetric analysis supported functionalization with an increase in percent weight loss for each functionalization, and the MWCNT surface functionalization determined pH‐dependent dispersibility. The nonfunctionalized MWCNT composites showed poor dispersion with transmission electron microscopy, and in sharp contrast, the functionalized composites displayed homogenous dispersions. Tensile testing revealed improved stress at break in the functionalized MWCNT composites at low loadings due to homogenous dispersion. POLYM. COMPOS., 37:1425–1434, 2016. © 2014 Society of Plastics Engineers     

Aminofunctionalization effect on the microtribological behavior of carbon nanotube/bismaleimide nanocomposites

Original multiwalled carbon nanotubes (O‐MWCNTs) and aminofunctionalized ethylenediamine‐treated multiwalled carbon nanotubes (MWCNTs‐EDA) were mixed with bismaleimide (BMI) resin to prepare O‐MWCNT/BMI and MWCNT‐EDA/BMI composites, respectively. Raman spectroscopy, thermogravimetric analysis, and infrared spectroscopy were used to investigate the influence of aminofunctionalization on the multiwalled carbon nanotube (MWCNT) framework. Dynamic mechanical analysis, scanning electron microscopy images of the fractured surface, and field emission scanning electron microscopy of the worn surface were used to determine the possible friction and wear mechanisms of the system. The MWCNT‐EDA/BMI composite exhibited a higher friction coefficient value and a lower wear loss rate value than the O‐MWCNT/BMI composite, which was attributed to the larger number of defects caused by the aminofunctionalization of the MWCNTs, the stronger interfacial adhesion formed between the MWCNTs‐EDA and the BMI resin, and the better dispersive state of the MWCNTs‐EDA in the BMI matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of multiwalled carbon nanotube/polyurethane composites via surface modification multiwalled carbon nanotubes using silane coupling agent

Well‐dispersed multiwalled carbon nanotubes/polyurethane (MWCNTs/PU) composites were synthesized in situ polymerization based on treating MWCNTs with nitric acid and silane coupling agent. The morphology and degree of dispersion of the MWCNTs were studied using a high resolution transmission electron microscopy (HR‐TEM) and X‐ray powder diffraction (XRD). The result showed that MWCNTs could be dispersed still in the PU matrix well with the addition of 2 wt% MWCNTs. The thermal and mechanical properties of the composites were characterized by dynamic mechanical thermal analysis, thermogravimetric analysis, tensile, and impact testing. The result suggested that the glass transition temperature (T_g) of composites increased greatly with increasing MWCNTs content slightly, and the MWCNTs is also helpful to improve mechanical properties of composites. Furthermore, the composites have an excellent mechanical property with the addition of 0.5 wt% MWCNTs. The electrical property testing indicates that the MWCNTs can improve evidently the electrical properties of composites when adding 1 wt% MWCNTs to the PU matrix. The volume resistivity of composites reaches to an equilibrium value. POLYM. COMPOS., 33:1866–1873, 2012. © 2012 Society of Plastics Engineers     

Influence of aminosilane‐functionalized carbon nanotubes on the rheometric,mechanical, electrical and thermal degradation properties of epoxidized natural rubber nanocomposites

We describe the preparation, characterization and physical properties of multiwalled carbon nanotube (MWCNT)‐filled epoxidized natural rubber (ENR) composites. To ensure better dispersion in the elastomer matrix, the MWCNTs were initially subjected to aminopropyltriethoxysilane (APS) treatment to bind amine functional groups (?NH₂) on the nanotube surface. Successful grafting of APS on the MWCNT surface through Si–O–C linkages was confirmed using Fourier transform infrared spectroscopy. Grafting of APS on the MWCNT surface was further corroborated using elemental analysis. ENR nanocomposites with various filler loadings were prepared by melt compounding to generate pristine and APS‐modified MWCNT‐filled elastomeric systems. Furthermore, we determined the effects of various filler loadings on the rheometric, mechanical, electrical and thermal degradation properties of the resultant composite materials. Rheometric cure characterization revealed that the torque difference increased with pristine MWCNT loading compared to the gum system, and this effect was more pronounced when silane‐functionalized MWCNTs were loaded, indicating that this effect was due to an increase in polymer–carbon nanotube interactions in the MWCNT‐loaded materials. Loading of silane‐functionalized MWCNTs in the ENR matrix resulted in a significant improvement in the mechanical, electrical and thermal degradation properties of the composite materials, when compared to gum or pristine MWCNT‐loaded materials.© 2013 Society of Chemical Industry     

A liquid‐like multiwalled carbon nanotube derivative and its epoxy nanocomposites

Multiwall carbon nanotubes (MWCNTs) with liquid‐like behavior at room temperature were prepared with sulfonic acid terminated organosilanes as corona and tertiary amine as canopy. The liquid‐like MWCNT derivative had low viscosity at room temperature (3.89 Pa s at 20°C) and exhibited non‐Newtonian shear‐thinning behavior. The weight fraction of MWCNT in the derivative was 16.72%. The MWCNT derivative showed very good dispersion in organic solvents, such as ethanol and acetone. The liquid‐like MWCNT derivative was incorporated into epoxy matrix to investigate the mechanical performance of the nanocomposites and the distribution of MWCNTs in the matrix. When the liquid‐like MWCNT derivative content was up to 1 wt %, the flexural strength and impact toughness of composites were 12.1 and 124% higher than the pure epoxy matrix, respectively. Transmission electron microscope (TEM) confirmed the very good dispersion of the liquid‐like MWCNT derivative in epoxy matrix. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2217–2224, 2013     

Effect of carbon nanotube on PA6/ECO composites: Morphology development,rheological, and thermal properties

Thermoplastic elastomer (TPE) nanocomposites based on polyamide‐6 (PA6)/poly(epichlorohydrin‐co‐ethylene oxide) (ECO)/multiwall carbon nanotube (MWCNTs) were prepared by melt compounding process. Different weight ratios of ECO (20, 40, and 60 wt %) and two kinds of functionalized and non‐functionalized MWCNTs were employed to fabricate the nanocomposites. The morphological, rheological, and mechanical properties of MWCNTs‐filled PA6/ECO blends were studied. The scanning electron microscopy of PA6/ECO blends showed that the elastomer particles, ECO, are well‐dispersed within the PA6 matrix. The significant improvement in the dispersibility of the carboxylated carbon nanotubes (COOH‐MWCNTs) compared to that of non‐functionalized MWCNTs (non‐MWCNTs) was confirmed by transmission electron microscopy images. The tensile modulus of samples improved with the addition of both types of MWCNTs. However, the effect of COOH‐MWCNTs was much more pronounced in improving mechanical properties of PA6/ECO TPE nanocomposites. Crystallization results demonstrated that the MWCNTs act as a nucleation agent of the crystallization process resulted in increased crystallization temperature (T_c) in nanocomposites. Rheological characterization in the linear viscoelastic region showed that complex viscosity and a non‐terminal storage modulus significantly increased with incorporation of both types of MWCNTs particularly at low frequency region. The increase of rheological properties was more pronounced in the presence of carboxylic (COOH) functional groups, in the other words by addition of COOH‐MWCNTs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45977.     

Microstructure,thermal, physico–mechanical and tribological characteristics of molybdenum disulphide‐filled polyamide 66/carbon black composites

With an objective to investigate the influence of molybdenum disulphide (MoS₂) on physico–mechanical and tribological properties of polyamide 66 (PA 66), was compounded with MoS₂ in the presence of carbon black (CB). The compounded material was injection molded to make test specimens to evaluate physico–mechanical, thermal, and tribological (wear, friction, and laser etching) characteristics. It was found that tensile strength, percentage elongation at break, and tensile modulus of PA 66/CB/MoS₂ composite increased linearly with increase in MoS₂ content. The impact strength of the PA 66 matrix increased from 37.2 to 43.2 J/m with an increase in MoS₂ content. The wear behavior of PA 66/CB/MoS₂ composites have been investigated under dry sliding conditions at different normal loads, sliding distances, and sliding velocities at room temperature. It was found that the introduction of MoS₂ in the presence of CB has certainly reduced the friction, wear behavior of PA 66 with improvement in laser etching resistance. MoS₂ could increase the adhesion between the transfer film and the counterface surface. The ability of the synergistic fillers in helping the formation of thin, uniform, and continuous transfer film would contribute to enhance the wear resistance of PA 66 composites. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Noncovalent functionalization of multi-walled carbon nanotubes with pyrene-linked nylon66 for high performance nylon66/multi-walled carbon nanotube composites

A new interfacial agent, 1-pyrenebutyric chloride (PBC), was synthesized for use in nylon 66 (PA66)/multi-walled carbon nanotube (MWCNT) composites. It has been shown that the pyrene units in PBC adsorb onto the MWCNT surface by physisorption, and the acyl chloride units in PBC react with amine end groups in PA66 during melt extrusion. As a result, PBC that was covalently bonded with PA66 formed at the interface between the MWCNT and PA66 matrix. The PA66/MWCNT composite containing PBC exhibited the best interfacial adhesion between MWCNT and PA66 and the highest level of MWCNT dispersion in the PA66 matrix among the composites examined. It was also found that the PA66/MWCNT composite with the higher interfacial adhesion energy between PA66 and MWCNT exhibited a higher level of reinforcement.     

Mechanical and tribological properties of PA66/PPS blend. III. Reinforced with GF

Based on previous work, 70 vol % PA66/30 vol % PPS blend was selected as a matrix, and the PA66/PPS blend reinforced with different content of glass fiber (GF) was prepared in this study. The mechanical properties of PA66/PPS/GF composites were studied, and the tribological behaviors were tested on block‐on‐ring sliding wear tester. The results showed that 20–30 vol % GF greatly increases the mechanical properties of PA66/PPS blend. When GF content is 20 vol %, the friction coefficient of composite is the lowest (0.35), which is decreased by 47% in comparison with the unfilled blend. The wear volume of the GF‐reinforced PA66/PPS blend composite decreases with the increase of GF content. However, the wear‐resistance is not apparently improved by the addition of GF in the experimental range for comparison with unfilled PA66/PPS blend. The worn surface and the transfer film on the counterface were examined by scanning electron microscopy (SEM). The observations revealed that the friction coefficient of composite depends on the formation and development of a transfer film. The wear mechanism involves polymer matrix wear and fiber wear. The former consists of melting wear and plastic deformation of the matrix, while the latter includes fiber sliding wear, cracking, rupturing, and pulverizing. The contributions of the matrix wear and the fiber wear determine the ultimate wear volume of PA66/PPS/GF composite. In addition, the abrasive action caused by the ruptured glass fiber is also a very important factor. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 523–529, 2006     

Improving tensile strength and toughness of melt processed polyamide 6/multiwalled carbon nanotube composites by in situ polymerization and filler surface functionalization

The effect of processing method and condition on the dispersion status of multiwalled carbon nanotubes (MWCNTs), and mechanical properties of the MWCNT/polyamide 6 (PA6) composites are investigated. Different melt processing conditions are used to dilute the master batch produced by melt process or in situ polymerization. Both MWCNTs and carboxyl group functionalized MWCNTs (MWCNTs‐COOH) are compounded with PA6 at different loadings (0.1, 0.25, 0.5, and 0.75 wt %) to study the effect of chemical modification of MWCNTs on the mechanical properties of the final composites. It is demonstrated that chemical modification of MWCNTs has a positive effect on the strength of the composites as an increase of 5–10 MPa was observed. More importantly, a near 5 MPa increase in strength and more importantly, a maximum of 138% increase in strain at break were observed for the composites produced by in situ polymerization, indicating a toughening and strengthening effect of CNT on the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tribological behavior of polyamide 66‐based binary and ternary composites

Friction and wear characteristics of polyamide 66 (PA66) and the composites of organoclay modified by styrene–ethylene/butylene–styrene triblock copolymer grafted with 1.84 wt% of maleic anhydride (SEBS‐g‐MA) were studied using an Universal Micro Tribometer reciprocating friction and wear tester. The morphologies of the wear tracks of PA66 and the composites were observed using a scanning electron microscope. The results showed that plastic deformation induced by the traction of the harder steel ball occurred on the worn surfaces of PA66 and the composite which were reinforced by SEBS‐g‐MA copolymer. It was found that the average frictional coefficient and specific wear rate of PA66/SEBS‐g‐MA binary composite are lowest under the same conditions. This indicates that toughness and wear resistance of PA66 matrix are improved with the incorporation of SEBS‐g‐MA copolymer. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Effect of amino‐functionalization of multi‐walled carbon nanotubes on the dispersion with epoxy resin matrix

Amino‐functionalization of multiwalled carbon nanotubes (MWCNTs) was carried out by grafting triethylenetetramine (TETA) on the surfaces of MWCNTs through the acid–thionyl chloride way. The amino‐functionalized MWCNTs show improved compatibility with epoxy resin and, as a result, more homogenous dispersion in the matrix. The mechanical, optical, and thermal properties of the amino‐functionalized MWCNT/epoxy composites were also investigated. It was found that introducing the amino‐functionalized MWCNTs into epoxy resin greatly increased the charpy impact strength, glass transition temperature, and initial decomposing temperature of cured epoxy resin. In addition, introducing unfunctionalized MWCNTs into epoxy resin was found greatly depressing the light transmission properties, which would affirmatively confine the application of the MWCNTs/epoxy composites in the future, while much higher light transmittance than that of unfunctionalized MWCNTs/epoxy composites was found for amino‐functionalized MWCNTs/epoxy composites. SEM of the impact cross section and TEM of ultrathin film of the amino‐functionalized MWCNTs/epoxy composites showed that the amino‐functionalized MWCNTs were wetted well by epoxy matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 97–104, 2006     

Crystallization and mechanical behavior of covalent functionalized carbon nanotube/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) nanocomposites

To improve the dispersity of multi‐walled carbon nanotubes (MWCNTs) in poly(3‐hydroxybutyrate‐co?3‐hydroxyvalerate) (PHBV) matrix, MWCNTs functionalized with carboxyl groups, hydroxyl groups, and atactic poly (3‐hydroxybutyrate) (ataPHB) through acid oxidation, esterification reaction, and “grafting from” method, respectively, were used to fabricate nanofiller/PHBV nanocomposites. The crystallization behavior, dispersion of MWCNTs before and after functionalization in PHBV matrices, and mechanical properties of a series of nanocomposites were investigated. The differential scanning calorimetry, wide‐angle X‐ray diffraction, and polarized optical microscope results suggested that the four types of MWCNTs acted as effective heterogeneous nucleation agents, inducing an increase in the crystallization rate, crystallinity, and crystallite size. Scanning electron microscope observations demonstrated that functionalized MWCNTs showed improved dispersion comparing with MWCNTs, suggesting an enhanced interfacial interaction between PHBV and functionalized MWCNTs. Consequently, the mechanical properties of the functionalized MWCNTs/PHBV nanocomposites have been improved as evident from dynamic mechanical and static tensile tests. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42136.     

Extension‐induced mechanical reinforcement in melt‐spun fibers of polyamide 66/multiwalled carbon nanotube composites

In this work, polyamide 66 (PA66) and its composites with multiwalled carbon nanotubes (MWNTs) were melt spun into fibers at different draw ratios. PA66 fibers at high draw ratio demonstrate a 40% increase in tensile strength, 66% increase in modulus and a considerable increase in toughness. It is demonstrated that this reinforcement can be mainly attributed to high‐draw‐ratio‐induced good dispersion and orientation of MWNTs, particularly the enhanced interfacial adhesion between MWNT and matrix thanks to interfacial crystallization. Our work provides a simple but efficient method to achieve good dispersion and strong interfacial interaction through melt spinning. Copyright © 2011 Society of Chemical Industry