Enhanced electrical properties of polycarbonate/carbon nanotube nanocomposites prepared by a supercritical carbon dioxide aided melt blending method

Polycarbonate/carbon nanotube (CNT) nanocomposites were generated using a supercritical carbon dioxide (scCO₂) aided melt blending method, yielding nanocomposites with enhanced electrical properties and improved dispersion while maintaining the aspect ratio of the as-received CNTs. Baytubes^® C 150 P CNTs were benignly deagglomerated with scCO₂ resulting in 5 fold (5X), 10X and 15X decreases in bulk density from the as-received CNTs. This was followed by melt compounding with polycarbonate to generate the CNT nanocomposites. Electrical percolation thresholds were realized at CNT loading levels as low as 0.83 wt% for composites prepared with 15X CNT using the scCO₂ aided melt blending method. By comparison, a concentration of 1.5 wt% was required without scCO₂ processing. Optical microscopy, transmission electron microscopy, and rheology were used to investigate the dispersion and mechanical network of CNTs in the nanocomposites. The dispersion of CNTs generally improved with scCO₂ processing compared to direct melt blending, but was significantly worse than that of twin screw melt compounded nanocomposites reported in the literature. A rheologically percolated network was observed near the electrical percolation of the nanocomposites. The importance of maintaining longer carbon nanotubes during nanocomposite processing rather than focusing on dispersion alone is highlighted in the current efforts.     

Electrical and thermal conductivity and tensile and flexural properties of carbon nanotube/polycarbonate resins

Adding conductive carbon fillers to insulating thermoplastic polymers increases the resulting composite's electrical conductivity. Carbon nanotubes (CNTs) are very effective at increasing composite electrical conductivity at low loading levels without compromising composite tensile and flexural properties. In this study, varying amounts (2–8 wt %) of CNTs were added to polycarbonate (PC) by melt compounding, and the resulting composites were tested for electrical conductivity (1/electrical resistivity), thermal conductivity, and tensile and flexural properties. The percolation threshold was less than 1.4 vol % CNT, likely because of CNTs high aspect ratio (1000). The addition of CNT to PC increased the composite electrical and thermal conductivity and tensile and flexural modulus. The 6 wt % (4.2 vol %) CNT in PC resin had a good combination of properties for electrical conductivity applications. The electrical resistivity and thermal conductivity were 18 Ω‐cm and 0.28 W/m · K, respectively. The tensile modulus, ultimate tensile strength (UTS), and strain at UTS were 2.7 GPa, 56 MPa, and 2.8%, respectively. The flexural modulus, ultimate flexural strength, and strain at ultimate flexural strength were 3.6 GPa, 125 MPa, and 5.5%, respectively. Ductile tensile behavior is noted in pure PC and in samples containing up to 6 wt % CNT. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermally induced phase separation in PαMSAN/PMMA blends in presence of functionalized multiwall carbon nanotubes: Rheology, morphology and electrical conductivity

The focus of this work is the evaluation and analysis of the state of dispersion of functionalized multiwall carbon nanotubes (CNTs), within different morphologies formed, in a model LCST blend (poly[(α-methylstyrene)-co-(acrylonitrile)]/poly(methyl-methacrylate), PαMSAN/PMMA). Blend compositions that are expected to yield droplet-matrix (85/15 PαMSAN/PMMA and 15/85 PαMSAN/PMMA, wt/wt) and co-continuous morphologies (60/40 PαMSAN/PMMA, wt/wt) upon phase separation have been combined with two types of CNTs; carboxylic acid functionalized (CNTCOOH) and polyethylene modified (CNTPE) up to 2 wt%. Thermally induced phase separation in the blends has been studied in-situ by rheology and dielectric (conductivity) spectroscopy in terms of morphological evolution and CNT percolation. The state of dispersion of CNTs has been evaluated by transmission electron microscopy. The experimental results indicate that the final blend morphology and the surface functionalization of CNT are the main factors that govern percolation. In presence of either of the CNTs, 60/40 PαMSAN/PMMA blends yield a droplet-matrix morphology rather than co-continuous and do not show any percolation. On the other hand, both 85/15 PαMSAN/PMMA and 15/85 PαMSAN/PMMA blends containing CNTPEs show percolation in the rheological and electrical properties. Interestingly, the conductivity spectroscopy measurements demonstrate that the 15/85 PαMSAN/PMMA blends with CNTPEs that show insulating properties at room temperature for the miscible blends reveal highly conducting properties in the phase separated blends (melt state) as a result of phase separation. By quenching this morphology, the conductivity can be retained in the blends even in the solid state.     

The characteristics of carbon nanotube‐reinforced poly(phenylene sulfide) nanocomposites

Multiwall carbon nanotube reinforced poly (phenylene sulfide) (PPS) nanocomposites were successfully fabricated through melt compounding. Structural, electrical, thermal, rheological, and mechanical properties of the nanocomposites were systematically studied as a function of carbon nanotube (CNT) fraction. Electrical conductivity of the polymer was dramatically enhanced at low loading level of the nanotubes; the electrical percolation threshold lay between 1 and 2 wt % of the CNTs. Rheological properties of the PPS nanocomposites also showed a sudden change with the CNT fraction; the percolation threshold was in the range of 0–0.5 wt % of CNTs. The difference in electrical and rheological percolation threshold was mainly due to the different requirements needed in the carbon nanotube network in different stages. The crystallization and melting behavior of CNT‐filled PPS nanocomposites were studied with differential scanning calorimetry; no new crystalline form of PPS was observed in the nanocomposites, but the crystallization rate was reduced. The thermal and mechanical properties of the nanocomposites were also investigated, and both of them showed significant increase with CNT fraction. For 5 wt % of CNT‐filled PPS composite, the onset of degradation temperature increased by about 13.5°C, the modulus increased by about 33%, and tensile strength increased by about 172%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of processing technique on the dispersion of carbon nanotubes within polypropylene carbon nanotube‐composites and its effect on their mechanical properties

Carbon nanotube‐reinforced polymer composites are being investigated as promising new materials having enhanced physical and mechanical properties. With regards to mechanical behavior, the enhancements reported thus far by researchers are lower than the theoretical predictions. One of the key requirements to attaining enhanced behavior is a uniform dispersion of the nanotubes within the polymer matrix. Although solvent mixing has been used extensively, there are concerns that any remaining solvent within the composite may degrade its mechanical properties. In this work, a comparison is carried out between solvent and “solvent‐free” dry mixing for dispersing multiwall carbon nanotubes in polypropylene before further melt mixing by extrusion. Various weight fractions of carbon nanotubes (CNTs) are added to the polymer and their effect on the mechanical properties of the resulting composites is investigated. Enhancements in yield strength, hardness, and Young's modulus when compared with the neat polymer, processed under similar conditions, are observed. Differences in mechanical properties and strain as a function of the processing technique (solvent or dry) are also clearly noted. In addition, different trends of enhancement of mechanical properties for the solvent and dry‐mixed extrudates are observed. Dry mixing produces composites with the highest yield strength, hardness, and modulus at 0.5 wt% CNT, whereas solvent mixing produces the highest mechanical properties at CNT contents of 1 wt%. It is believed that this difference is primarily dependent on the dispersion of CNTs within the polymer matrix which is influenced by the processing technique. Field emission scanning electron microscopy analysis shows the presence of clusters in large wt% CNT samples produced by dry mixing. Samples produced by solvent mixing are found to contain homogeneously distributed CNTs at all CNT wt fractions. CNT pull‐out is observed and may explain the limited enhancement in mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

The effect of carbon nanotubes on the rheology and electrical resistivity of polyamide 12/high density polyethylene blends

Different melt mixing sequences were applied to incorporate multiwalled carbon nanotubes (CNTs) into blends prepared from high density polyethylene (PE) and polyamide 12 (PA). Electron microscopy, rheology and electrical resistivity were used to characterize the morphology and microstructure. At a composition of 75PA/25PE, presence of CNT at the interface promoted by premixing the CNTs in the PE phase, resulted in finer phase morphology and a decrease in the resistivity of up to five decades relative to other mixing procedures used. At a composition of 25PA/75PE, premixing the CNT in the PA phase resulted in their segregation inside and around the PA domains and a four decade lower resistivity. Interestingly, compounds that yielded the lowest resistivity were also characterized by increased low frequency melt storage modulus (G′) which indicates the existence of a correlation between the two properties.     

Synergistic effect of graphene and carbon nanotube on lap shear strength and electrical conductivity of epoxy adhesives

In this study, synergy between graphene platelets (GnPs) and carbon nanotubes (CNTs) in improving lap shear strength and electrical conductivity of epoxy composite adhesives is demonstrated. Adding two-dimensional GnPs with one-dimensional CNTs into epoxy matrix helped to form global three-dimensional network of both GnPs and CNTs, which provide large contact surface area between the fillers and the matrix. This has been evidenced by comparing the mechanical properties and electrical conductivity of epoxy/GnP, epoxy/CNT, and epoxy/GnP-CNT composites. Scanning electron microscopic images of lap shear fracture surfaces of the composite adhesives showed that GnP-CNT hybrid nanofillers demonstrated better interaction to the epoxy matrix than individual GnP and CNT. The lap shear strength of epoxy/GnP-CNT composite adhesive was 89% higher than that of the neat epoxy adhesive, compared with only 44 and 30% increase in the case of epoxy/GnP and epoxy/CNT composite adhesives, respectively. Electrical percolation threshold of epoxy/GnP-CNT composite adhesive is recorded at 0.41 vol %, which is lower than epoxy/GnP composite adhesive (0.58 vol %) and epoxy/CNT composite adhesive (0.53 vol %), respectively. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48056.     

Using supercritical carbon dioxide in preparing carbon nanotube nanocomposite: Improved dispersion and mechanical properties

Improvements in carbon nanotube (CNT) dispersion and subsequent mechanical properties of CNT/poly(phenylsulfone) (PPSF) composites were obtained by applying the supercritical CO₂ (scCO₂)‐aided melt‐blending technique that has been used in our laboratory for nanoclay/polymer composite preparation. The preparation process relied on rapid expansion of the CNTs followed by melt blending using a single‐screw extruder. Scanning electronic microscopy results revealed that the CNTs exposed to scCO₂ at certain pressures, temperatures, exposure time, and depressurization rates have a more dispersed structure. Microscopy results showed improved CNT dispersion in the polymer matrix and more uniform networks formed with the use of scCO₂, which indicated that CO₂‐expanded CNTs are easier to disperse into the polymer matrix during the blending procedure. The CNT/PPSF composites prepared with scCO₂‐aided melt blending and conventional melt blending showed similar tensile strength and elongation at break. The Young's modulus of the composite prepared by means of conventional direct melt blending failed to increase beyond the addition of 1 wt% CNT, but the scCO₂‐aided melt‐blending method provided continuous improvements in Young's modulus up to the addition of 7 wt% CNT. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Comparison of Exfoliated Graphite Nanoplatelets (xGnP) and CNTs for Reinforcement of EVA Nanocomposites Fabricated by Solution Compounding Method and Three Screw Rotating Systems

Exfoliated graphite nanoplatelet (xGnP?) and carbon nanotube (CNT)-reinforced ethylene vinyl acetate (EVA) nanocomposites have been fabricated by three screw rotating systems: co-, counter- and modified-co-rotating. The highest tensile strength and modulus were shown by the composites, both xGnP- and CNT-loaded, made by counter-rotating. The counter-rotating process produced better dispersion than the other two as found in morphology studies by environmental scanning electron microscopy (ESEM). However, the rotating system did not affect the electrical conductivity. The percolation threshold of the xGnP–EVA nanocomposites formed by solution mixing and injection molding was between 14–16 wt%, due to the advantageous effect of sheets with higher aspect ratios compared with spherical or elliptical fillers in forming conducting networks in the polymer matrix. Although CNT–EVA was electrically conductive with only 5 wt% CNT loading, we recommend xGnP as a more suitable additive material for polymer composites. xGnP greatly increased the thermal stability of xGnP–EVA composites to be applied as adhesives, films and cables.     

Fabrication and properties of carbon nanotube/styrene–ethylene–butylene–styrene composites via a sequential process of (electrostatic adsorption aided dispersion)‐plus‐(melt mixing)

Carbon nanotube (CNT)/styrene–ethylene–butylene–styrene (SEBS) composites were prepared via a sequential process of (electrostatic adsorption assisted dispersion)‐plus‐(melt mixing). It was found that CNTs were uniformly embedded in SEBS matrix and a low percolation threshold was achieved at the CNT concentration of 0.186 vol %. According to thermal gravimetric analysis, the temperatures of 20% and 50% weight loss were improved from 316°C and 352°C of pure SEBS to 439°C and 463°C of the 3 wt % CNT/SEBS composites, respectively. Meanwhile, the tensile strength and elastic modulus were improved by about 75% and 181.2% from 24 and 1.6 MPa of pure SEBS to 42 and 4.5 MPa of the 3 wt % CNT/SEBS composite based on the tensile tests, respectively. Importantly, this simple and low‐cost method shows the potential for the preparation of CNT/polymer composite materials with enhanced electrical, mechanical properties, and thermal stability for industrial applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40227.     

Electrical conductivity and infrared radiation performance of SiC-CNT composite ceramics

SiC ceramic is an excellent infrared source material that can be used in a wide range of fields, like infrared heating, night vision and communication, but its poor electrical properties limit it. In this work, carbon nanotubes (CNTs) were selected as conductive phase filler, and SiC-CNT composite ceramics were prepared by SPS method. The effects of CNT content on the microstructures, electrical properties and infrared radiation performance of the composites were studied. The introduction of CNT effectively reduced the height of Schottky barrier at grain boundary, thus weakening the grain boundary effect, reducing the grain boundary resistance, further weakening the nonlinear characteristics and bulk resistivity of the composite ceramics. When the content of CNT was 1 wt%, electrical percolation was achieved, and the bulk resistivity of SiC ceramics dropped by nearly 3 orders of magnitude. The preferred orientation distribution of CNT made the bulk resistivity perpendicular to the pressure direction R_⊥ always lower than that parallel to the pressure direction R_//. The sample with 5 wt% CNT assumed linear conductivity characteristics, with bulk resistivity in different direction of 16.5 Ω cm (R_//) and 11.8 Ω cm (R_⊥), respectively. CNT addition slightly increased the infrared radiation performance of SiC ceramics, and the sample with 5 wt% CNT possessed the highest total emissivity of 0.675. The excellent electrical conductivity and infrared radiation performance of SiC-CNT composite ceramic confirmed this class as a promising infrared source material.     

High strength micron size carbon fibers from polyacrylonitrile–carbon nanotube precursors

An improved, high strength, carbon fiber derived from islands-in-a-sea bi-component gel spun polyacrylonitrile (PAN)–carbon nanotube (CNT) precursor fibers containing 1 wt% mixture of single, double, and few walled CNTs was developed. Microscale experiments with properly designed MEMS tools provided the mechanical properties of individual, 1-μm diameter carbon filaments, which were isolated from bundles of 407 fibers. The statistics of the mechanical strength were described well by the cumulative Weibull probability density function that resulted in characteristic strength of 6.2 GPa and a Weibull modulus of 4.5, while the highest tensile strength and Young’s modulus values were 7.3 GPa and 318 GPa, respectively. At the lower end of the spectrum, the strength values correlated well with predictions based on an effective flaw size obtained from fracture cross-sections. On the other hand, the failure cross-sections of the high strength carbon fibers contained a large number of long and oriented CNTs but no discernible flaws. The high interfacial strength between the CNTs and the surrounding carbon resulted in fracture and telescopic pull-out of the CNTs, which was corroborated by individual CNT pull-out experiments with MEMS tools inside an SEM, and in situ fiber failure observations of telescopic pull-out of CNTs inside a TEM.     

Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Assessment of intertube interactions in different functionalized multiwalled carbon nanotubes incorporated in a phenoxy resin

In this work, about 1 wt% of different functionalized carbon nanotubes (CNTs), namely CNT? COOH (CNT with carboxylic groups), CNT? NH₂ (CNT with amine groups) and CNT? OH (CNT with hydroxyl groups), as well as nonfunctionalized CNTs were incorporated into a phenoxy resin via a melt mixing process. The extent of intertubes and polymer–tubes interactions and their influence on state of CNTs dispersion were assessed through determination of electrical, rheological, and morphological characteristics. CNT? NH₂ showed the lowest intertubes interactions followed by CNT? OH and CNT? COOH. Nanocomposite made from CNT? COOH showed the poorest state of CNTs dispersion and the biggest CNTs agglomerates and it remained nonconductive. The acid‐functionalized CNTs were not able to form strong polymer–tube interactions because of their high cohesive energy and therefore in the melt rheological investigations they exhibited the lowest storage modulus and complex viscosity as well as the highest loss factor among all the studied CNTs. A good balance between intertubes and polymer–tube interactions is necessary through proper selection of CNTs functional groups for achieving a good state of CNTs dispersion and consequently obtaining enhanced electrical and viscoelastic properties. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Morphology, structure and properties of conductive PS/CNT nanocomposite electrospun mat

The morphologies and properties of Polystyrene (PS)/Carbon Nanotube (CNT) conductive electrospun mat were studied in this paper. Nanocomposite fibers were obtained through electrospinning of PS/Di-Methyl Formamide (DMF) solution containing different concentrations and types of CNTs. The dispersion condition of CNTs was correlated to morphologies and properties of nanocomposite fibers. A copolymer as an interfacial agent (SBS, Styrene-butadiene-styrene type) was used to modify the dispersion of CNTs in PS solution before electrospinning. The results showed that the presence of the copolymer significantly enhances CNT dispersion. The fiber diameters varied between 200 nm and 800 nm depending on CNT type, polymer concentration and copolymer. The final morphological study of the fibers showed that CNT addition caused a decrease in beads formation along fiber axis before percolation threshold. However, addition of CNTs above percolation increased the beads formation, depending on the dispersion condition. The presence of SBS modified the dispersion, reduced the fiber diameter and the number of bead structures. Electrical conductivity measurements on nanocomposite mats of 15-300 μm in thickness showed an electrical percolation threshold around 4 wt% MWCNT; while the samples containing SBS showed higher values of conductivities below percolation compared to the samples with no compatibilizer. Enhancement in mechanical properties was observed by the addition of CNTs at concentrations below percolation.     

Enhancement of electrical conductivity and other related properties of epoxidized natural rubber/carbon nanotube composites by optimizing concentration of 3‐aminopropyltriethoxy silane

Carbon nanotube (CNT)‐filled epoxidized natural rubber (ENR) composites were prepared by mixing in an internal mixer and thereafter on a two‐roll mill. Silane coupling agent, namely 3‐aminopropyltriethoxy silane (APTES), was directly incorporated in the ENR‐CNT composites during mixing of rubber and CNTs in the mixer, to perform in situ functionalization. It was found that pre‐crosslinking of ENR and APTES occurred especially at high APTES concentrations, such as 0.06 mL/(g of CNTs) and caused strong CNT agglomeration in the ENR matrix. However, the pre‐crosslinking could be reduced or avoided by decreasing the APTES concentration. In the concentration range 0.01–0.015 mL/(g of CNTs) of APTES, the APTES molecules were grafted on the CNT surfaces and generated new chemical linkages with the ENR. This improved the CNT dispersion in the ENR matrix and enhanced the composite properties. A very low approximately 0.5 phr of CNT threshold concentration for electric percolation was achieved in this type of composites. Also, three‐dimensional connected CNT networks were found to form in the ENR matrix at very low APTES levels. Thus, the electrical conductivity achieved in these composites reached the level required of conductive materials. POLYM. ENG. SCI., 57:381–391, 2017. © 2016 Society of Plastics Engineers     

Low percolation threshold in single-walled carbon nanotube/high density polyethylene composites prepared by melt processing technique

A new method was developed to disperse carbon nanotubes (CNTs) in a matrix polymer and then to prepare composites by melt processing technique. Due to high surface energy and strong adsorptive states of nano-materials, single-walled carbon nanotubes (SWNTs) were adsorbed onto the surface of polymer powders by spraying SWNT aqueous suspected solution onto fine high density polyethylene (HDPE) powders. The dried SWNTs/powders were blended in a twin-screw mixture, and the resulting composites exhibited a uniformly dispersion of SWNTs in the matrix polymer. The electrical conductivity and the rheological behavior of these composites were investigated. At low frequencies, complex viscosities become almost independent of the frequency as nanotubes loading being more than 1.5 wt%, suggesting an onset of solid-like behavior and hence a rheological percolation threshold at the loading level. However, the electrical percolation threshold is ∼4 wt% of nanotube loading. This difference in the percolation thresholds is understood in terms of the smaller nanotube-nanotube distance required for electrical conductivity as compared to that required to impede polymer mobility. The measurements of mechanical properties indicate that this processing method can obviously improve the tensile strength and the modulus of the composites.     

Multiwalled carbon nanotube/polysulfone composites: Using the Hildebrand solubility parameter to predict dispersion

Polysulfone composites were prepared by solution casting, using various types of treated carbon nanotubes (CNTs) at loadings of up to 5 wt%. The CNT types tested were: as‐received, acid treated, OCA surfactant, OCA functionalized and Poly(methyl methacrylate) functionalized nanotubes prepared using both as‐received and acid treated CNT. The treatment types investigated were selected based upon their solubility parameters and on the results of previous studies. The treated CNTs, CNT/solvent dispersions and the final composite samples were characterised using Fourier Transform Infrared Spectroscopy (FTIR), thermal analysis, Transmission Electron Microscopy (TEM), Ultraviolet‐Visible (UV‐vis) spectroscopy, optical microscopy, electrical conductivity and tensile testing. It was observed that the all the treatments studied improved the stability of CNT in the solvent. Of the CNT types studied, composites containing OCA functionalised CNT displayed the lowest percolation threshold (3 wt%) and highest mechanical performance. While the use of Hildebrand solubility parameters is useful in indentifying promising CNT treatments, their use can not fully predict CNT dispersion behaviour and composite performance. It is also critical to consider the influence of any treatments on CNT length and residual solvent levels. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Structure and properties of polypropylene‐wrapped carbon nanotubes composite

By means of in situ graft method, polypropylene (PP)‐wrapped carbon nanotubes (CNTs) composite were prepared. Infrared spectroscopy (IR) results showed that there was covalent linkage between PP and CNTs via maleic anhydride (MAH) grafting. Owing to the uniform dispersion of CNTs and covalent adhesion between PP and CNTs, the tensile strength of PP‐wrapped CNTs composite was higher than that for neat PP by 110%, and a 74% increase as compared to the CNTs/PP (with the same CNTs content) composite. The further test showed a strong mechanical behavior with up to 113% increase in Young's modulus of the neat PP. Based on the uniform dispersion of CNTs, the electrical conductivity of PP‐wrapped CNTs composite increased sharply by up to seven orders of magnitude with 4 wt % CNT fillers. As a result, the volume resistivity was decreased with increase in the CNT content that could be governed in a percolation‐like power law with a relatively low percolation threshold. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Surfactant‐assisted processing of polyimide/multiwall carbon nanotube nanocomposites for microelectronics applications

The dispersion and stability of carbon nanotubes (CNTs) inside a polymer matrix, especially with a high CNT content, are still big challenges. Moreover, the interaction between CNTs and the polymer matrix should be strong enough to improve the mechanical properties. The efficient dispersion of CNTs is essential for the formation of a uniform distribution of a CNT network in a polymer composite. Polyimide/multiwall CNT nanocomposites were synthesized by in situ polymerization with the aid of a surfactant. A Fourier transform infrared spectroscopy study proved that the surfactant did not hamper the polymerization of the polyimide. The microstructure, storage modulus and electrical conductivity of the nanocomposites were improved using a particular amount of the surfactant. Environmental stability test results showed that the polyimide with 1 wt% of CNTs produced with the aid of the surfactant possessed excellent reliability in high‐temperature and high‐humidity environments. Surfactants were successfully used to obtain fine‐structure polyimide/CNT nanocomposites by in situ polymerization. The enhancement of the mechanical properties was attributed to the incorporation of the surfactant. A percolation of electrical conductivity could be achieved with 1 wt% of CNTs. Copyright © 2010 Society of Chemical Industry