Electrical conductivity modeling of carbon black/polycarbonate,carbon nanotube/polycarbonate,and exfoliated graphite nanoplatelet/polycarbonate composites

Adding conductive carbon fillers to electrically insulating thermoplastic polymers increases the resulting composite's electrical conductivity, which would enable them to be used in electrostatic dissipative and semiconductive applications. In this study, varying amounts of carbon black (CB: 2 to 10 wt %), multiwalled carbon nanotubes (CNT: 0.5 to 8 wt %), or exfoliated graphite nanoplatelets (GNP: 2 to 15 wt %) were added to polycarbonate (PC) and the resulting composites were tested for electrical conductivity (EC = 1/electrical resistivity). The percolation threshold was ～ 1.2 vol % CNT, ～ 2.4 vol % CB, and ～ 4.6 vol % GNP. In addition, three EC models (Mamunya, additive, and general effective media) were developed for the CB/PC, CNT/PC, and GNP/PC composites. The general effective media (GEM) model showed the best agreement with the experimental results over the entire range of filler concentrations (above and below the percolation threshold) for all three composite systems. In addition, the GEM model can be easily adapted for composites containing combinations of different conductive fillers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of styrene–acrylonitrile on the electrical resistivity of polycarbonate/multiwalled carbon nanotube composites

Multiwalled carbon nanotube (MWCNT)‐filled polycarbonate (PC)/styrene–acrylonitrile (SAN) blends with a wide range of blend compositions were prepared by melt mixing in a rotational rheometer, and the effect of SAN on the electrical properties of the PC/MWCNT composites was studied. The structure/electrical property relationship was investigated and explained by a combination of MWCNT localization and blend morphology. Transmission electron micrographs showed selective localization of MWCNTs in the PC phase, regardless of the blend morphology. When the SAN concentration was 10–40 wt %, which corresponded to sea‐island (10–30 wt %) and cocontinuous (40 wt %) blend morphologies (PC was continuous in both structures), the electrical resistivity decreased with increases in the SAN content. The concept of an effective volume concentration of MWCNTs was used to explain this effect. When the SAN concentration was 70 wt % or higher, the electrical resistivity was very high because MWCNTs were confined in the isolated PC particles. In addition, SAN was replaced by other polymers [polystyrene, methyl methacrylate/styrene, and poly(methyl methacrylate)]; these yielded similar blend morphologies and MWCNT localization and showed the generality of the concept of effective concentration in explaining a decrease in the electrical resistivity upon the addition of a second polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Rheological and electrical properties of polycarbonate/multi-walled carbon nanotube composites

Rheological and electrical properties of the polycarbonate (PC)/multi-walled carbon nanotube (MWNT) were studied. The MWNT was funtoinalized by treating with the hydrogen peroxide (H₂O₂). The H₂O₂ treated MWNT was dried by thermal and freeze drying methods. From the morphological studies, the degree of entanglement of the MWNT was decreased after treating with the H₂O₂. For the H₂O₂ treated MWNT (thermal drying), the length of the MWNT was shortened compared that of the H₂O₂ treated MWNT (freeze drying). The rheological and electrical properties of the PC/MWNT (H₂O₂ treated) composites increased compared that of the PC/MWNT (untreated) composites. Also, the electrical conductivity showed higher value for the PC/MWNT (H₂O₂ treated, freeze drying) composites compared that of the PC/MWNT (H₂O₂ treated, thermal drying) composites. From the results of the morphological, rheological, and electrical properties of the PC/MWNT composites, it is suggested that the electrical and rheological properties of the PC/MWNT composites are affected by the MWNT-MWNT network structure, which is related with the MWNT morphologies such as the degree of aggregation and aspect ratio of the MWNT.     

Dynamic mechanical and morphological properties of polycarbonate/multi-walled carbon nanotube composites

Dynamic mechanical and morphological properties of the polycarbonate (PC)/multi-walled carbon nanotube (MWNT) composites were studied by dynamic mechanical thermal analysis (DMTA) and X-ray diffractometry, respectively. For the without annealed PC/MWNT composites containing the higher content of the MWNT (≥7.0 wt%), double tan δ peaks were observed, which could be explained by the phase separation morphology model. For the annealed PC/MWNT composites, a broad single tan δ peak was observed. From the X-ray diffraction of the annealed PC/MWNT composites, it was observed that more regular structure of the PC was obtained, which was consistent with the result of the thermal analysis of the annealed PC/MWNT composites. From the dynamic mechanical properties, thermal analysis, and X-ray diffraction of the annealed PC/MWNT composites, it is suggested that PC/MWNT composites show a broad single tan δ peak and partially crystalline structure of the PC in the PC/MWNT composites by annealing.     

Electrical conductivity of carbon black/single-wall carbon nanotube/low-density polyethylene ternary composite foam

In order to obtain high electrical conductive low-density polyethylene (LDPE) foam, carbon black (CB), single-wall carbon nanotube (SWCNT), and LDPE (CB/SWCNT/LDPE) ternary composite foams were successfully fabricated by chemical compression molding method. The electrical conductivity, mechanical properties, microstructure, density, and crystallinity of the foam were studied in detail. It can be found that CB and SWCNT have synergistic effect. For the CB/SWCNT/LDPE composite foam which containing 19 wt % CB and 0.05 wt % SWCNT, its density is only 0.082 g cm⁻¹ and the electrical conductivity can reach at 2.88 × 10⁻⁵ S cm⁻³, which is far more than 15 orders of magnitudes of pure polyethylene and 4 orders of magnitudes times higher than sample which CB content is 19 wt %. It is noteworthy that ultralow concentration of SWCNT could drastically improve the electrical conductivity and reduce the density of LDPE foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48382.     

Multiscale mechanical phenomena in electrospun carbon nanotube composites

The carbon nanotube (CNT) structure is a promising building block for future nanocomposite structures. Mechanical properties of the electrospun butadiene elastomer reinforced with CNT are analyzed by multiscale method. Nanofiber diameter dependence on electric field and solution concentration is estimated from experimental data. The fiber microscale effective properties are determined by homogenization procedure using modified shear‐lag model, while the point‐bonded stochastic fibrous network on the mesoscale replaced by continuum effective sheet. Random fibrous network was generated according experimentally determined stochastic quantifiers. The influence of CNT reinforcement on elastic modulus of electrospun sheet on macroscopic level is determined by finite element method. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

氟橡胶/碳纳米管复合材料的拉伸应力-应变行为

以氟橡胶/炭黑复合材料作对比研究了氟橡胶/碳纳米管复合材料的拉伸应力-应变、拉伸应力弛豫和拉伸应力软化行为。结果表明,碳纳米管对氟橡胶有良好的增强效果,相同用量碳纳米管的增强效果要高于炭黑,低应变时碳纳米管的增强效果更明显;与氟橡胶/炭黑复合材料相比,氟橡胶/碳纳米管复合材料的应力弛豫现象更为明显,应力弛豫速率更快;随着碳纳米管和炭黑用量的增加,复合材料的应力软化效应增大,氟橡胶/碳纳米管复合材料的应力软化效应明显高于氟橡胶/炭黑复合材料。     

Rheological behavior of multiwalled carbon nanotube/polycarbonate composites

The rheological behavior of compression molded mixtures of polycarbonate containing between 0.5 and 15 wt% carbon nanotubes was investigated using oscillatory rheometry at 260 °C. The nanotubes have diameters between 10 and 15 nm and lengths ranging from 1 to 10 μm. The composites were obtained by diluting a masterbatch containing 15 wt% nanotubes using a twin-screw extruder. The increase in viscosity associated with the addition of nanotubes is much higher than viscosity changes reported for carbon nanofibers having larger diameters and for carbon black composites; this can be explained by the higher aspect ratio of the nanotubes. The viscosity increase is accompanied by an increase in the elastic melt properties, represented by the storage modulus G′, which is much higher than the increase in the loss modulus G″. The viscosity curves above 2 wt% nanotubes exhibit a larger decrease with frequency than samples containing lower nanotube loadings. Composites containing more than 2 wt% nanotubes exhibit non-Newtonian behavior at lower frequencies. A step increase at approximately 2 wt% nanotubes was observed in the viscosity-composition curves at low frequencies. This step change may be regarded as a rheological threshold. Ultimately, the rheological threshold coincides with the electrical conductivity percolation threshold which was found to be between 1 and 2 wt% nanotubes.     

Synthesis and properties of poly(methyl methacrylate)/carbon nanotube composites covalently integrated through in situ radical polymerization

Poly(methyl methacrylate) (PMMA)/single‐walled carbon nanotube (SWNT) composites were synthesized by the grafting of PMMA onto the sidewalls of SWNTs via in situ radical polymerization. The free‐radical initiators were covalently attached to the SWNTs by a well‐known esterification method and confirmed by means of thermogravimetric analysis and Fourier transform infrared spectroscopy. Scanning electron microscopy and transmission electron microscopy were used to image the PMMA–SWNT composites; these images showed the presence of polymer layers on the surfaces of debundled, individual nanotubes. The PMMA–SWNT composites exhibited better solubility in chloroform than the solution‐blended composite materials. On the other hand, compared to the neat PMMA, the PMMA–SWNT nanocomposites displayed a glass‐transition temperature up to 6.0°C higher and a maximum thermal decomposition temperature up to 56.6°C higher. The unique properties of the nanocomposites resulted from the strong interactions between the SWNTs and the PMMA chains. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of nanoclays on electrical and morphological properties of thermoplastic polyurethane/multiwalled carbon nanotube/clay nanocomposites

Nanocomposites of thermoplastic polyurethanes (TPUs), multiwalled carbon nanotubes (MWCNTs) and clays were prepared via melt processing using polyether‐ and polyester‐based TPUs, MWCNTs, and organically modified nanoclays (Cloisite C30B and C25A). Coaddition of clays and MWCNTs to TPU nanocomposites increased their electrical conductivities above those without any clay. Nanoclay alone is shown to produce no effect on electrical conductivity. TEM results show that the coaddition of nanoclay affects the nanocomposite morphology by changing the MWCNT distribution. Clay C25A and MWCNTs were observed to form network structures in the nanocomposites, resulting in improved electrical conduction. Interaction between MWCNTs and clays as well as an increase in nanocomposite viscosity caused by the coaddition of clays may influence the morphology change. Most of the nanocomposites containing both MWCNTs and clay exhibited higher dielectric constants, indicating higher electrical conductivities. Tensile properties investigations confirmed the reinforcing effects of the MWCNTs and clays. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallization behavior of polyamide 11/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC) was used to investigate the isothermal and nonisothermal crystallization kinetics of polyamide11 (PA11)/multiwalled carbon nanotube (MWNTs) composites. The Avrami equation was used for describing the isothermal crystallization behavior of neat PA11 and its nanocomposites. For nonisothermal studies, the Avrami model, the Ozawa model, and the method combining the Avrami and Ozawa theories were employed. It was found that the Avrami exponent n decreased with the addition of MWNTs during the isothermal crystallization, indicating that the MWNTs accelerated the crystallization process as nucleating agent. The kinetic analysis of nonisothermal crystallization process showed that the presence of carbon nanotubes hindered the mobility of polymer chain segments and dominated the nonisothermal crystallization process. The MWNTs played two competing roles on the crystallization of PA11 nanocomposites: on the one hand, the MWNTs serve as heterogeneous nucleating agent promoting the crystallization process of PA11; on the other hand, the MWNTs hinder the mobility of the polymer chains thus retarding the crystal growth process of PA11. The activation energies of PA11/MWNTs composites for the isothermal and nonisothermal crystallization are lower than neat PA11. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Preparation and characterization of polymer/multiwall carbon nanotube/nanoparticle nanocomposites and preparation of their metal complexes

Carbon nanotube‐polymer nanocomposites were synthesized and characterized successfully. In this work, multiwall carbon nanotubes (MWCNT) were opened using HNO₃/H₂SO₄ mixture and filled by metal nanoparticles such as silver nanoparticles through wet‐chemistry method. The oxidized MWCNT were reacted subsequently with thionyl chloride, 1,6‐diaminohexane, producing MWNT‐amine functionalized. Then the MWCNT containing metal nanoparticles were used as a monomer with different weight percentages in melt polymerization with An and CNCl separately. Furthermore, the polyamide and polytriazine modified MWCNT were used for the preparation of metal ion complexes such as Fe⁺² and La⁺³. The structures and properties of nanocomposites were evaluated by TEM, DSC, TGA, and FT‐IR methods. The chelating behavior and sorption capacities of prepared nanocomposites were carried out by using some metal ions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrical resistivity of polycarbonate/multiwalled carbon nanotube composites under varying injection molding conditions

Multiwalled carbon nanotube (MWCNT)‐filled polycarbonate composites were prepared by a corotating intermeshing twin‐screw extruder. The surface resistivities of compression‐ and injection‐molded specimens were quite different, the difference ranging from 10³ to 10⁷ Ω/sq at varying MWCNT concentrations. The surface resistivity of the injection‐molded specimen at 2 wt % loading varied up to 10⁵ Ω/sq in the specimen thickness direction and up 10⁴ Ω/sq in the polymer flow direction with respect to the gate. The difference in surface resistivity with the positions of injection‐molded specimen was confirmed with the morphology, which showed the difference in MWCNT number density (numbers/surface area). There was no significant effect on surface resistivity with injection pressure, holding pressure, and molding temperature. The specimens prepared at the injection speed of 13 mm/s showed surface resistivities 10³–10⁴ Ω/sq depending on the positions, which was comparable with the compression‐molded specimens, which had a surface resistivity of 10³ Ω/sq. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Microwave absorbing properties of a radar absorbing structure composed of carbon nanotube papers/glass fabric composites

In this study, carbon nanotube papers were employed in fabricating thin and broadband radar absorbing structures (RAS). Different concentrations of the CNT papers have been made by using a vacuum filtration method, with 20 × 20 cm in size and 21-27 μm in thickness. An epoxy resin was added into the CNT paper and then cured to become a composite with 1-5 wt.% of CNTs and 83-309 μm in thickness. The complex permittivity and permeability (ε′, ε″, μ′, μ″) of the CNT paper composites were measured using the transmission/reflection method in the frequency range of 2-18 GHz. The results reveal that the real (ε′) and imaginary (ε″) parts of the complex permittivity are increased with the CNT concentration. The ε′ of 5 wt.% CNT sample reaches 323 at 2 GHz and then decreases to 49.0 at 18 GHz. The ε″ reaches 321 at 2 GHz and decreases to 26.0 at 18 GHz. The CNT paper composite combined with a glass fabric composite used for a dielectric spacer is fabricated for an innovative RAS and the reflection loss is measured using the arch method in a microwave anechoic chamber. The results show that the 5 wt.% CNT paper composite/glass fabric composite absorbers attain maximum reflection loss of −13.3 dB at 12.0 GHz, −13.8 dB  at 10.0 GHz, and −16.0 dB at 7.5 GHz for spacer thickness of 1.5, 2.0, and 3.0 mm, respectively.     

Electrical,rheological, and mechanical properties copolymer/carbon black composites

This work aims to evaluate the electrical conductivity and the rheological and mechanical properties of copolymer/carbon black (CB) conductive polymer composites (CPCs). The copolymers, containing ethylene groups in their structure, used as matrix were polyethylene grafted with maleic anhydride (PEgMA), ethylene-methyl acrylate–glycidyl methacrylate (EMA-GMA), and ethylene-vinyl acetate (EVA). For comparison purposes, bio-based polyethylene (BioPE)/CB composites were also studied. The electrical conductivity results showed that the electrical percolation threshold of BioPE/CB composite was 0.36 volume fraction of CB, whereas the rheological percolation threshold was 0.25 volume fraction of CB. The most conductive CPC was BioPE/CB. Among the copolymer/CB CPCs, PEgMA/CB showed the highest conductivity, which can be attributed to the fact that the PEgMA copolymer had higher crystallinity. It also has a higher amount of ethylene groups in its structure. Torque rheometry analysis indicated that EMA-GMA copolymer may have reacted with CB. Rheological measurements under oscillatory shear flow indicated the formation of a percolated network in BioPE/CB and copolymer/CB composites. Morphology analysis by scanning electron microscopy (SEM) indicated the formation of a percolated network structure in BioPE/CB composite and finely dispersed CB particles within the PEgMA copolymer. Wetting of CB particles/agglomerates by the copolymer matrix was observed in EVA/CB and EMA-GMA/CB composites. Conductive CB acted as reinforcing filler as it increased the elastic modulus and tensile strength of BioPE and the copolymers.     

Structure and crystallization behavior of Nylon 66/multi-walled carbon nanotube nanocomposites at low carbon nanotube contents

Multi-walled carbon nanotubes (MWNTs) were modified with poly(hexamethylene adipamide) (also known as Nylon 66) via a controlled polymer solution crystallization method. A “nanohybrid shish kebab” (NHSK) structure was found wherein the MWNT resembled the shish while Nylon 66 lamellar crystals formed the kebabs. These Nylon 66-functionalized MWNTs were used as precursors to prepare polymer/MWNT nanocomposites. Excellent dispersion was revealed by optical and electron microscopies. Nitric acid etching of the nanocomposites showed that MWNT formed a robust network in Nylon 66. Non-isothermal DSC results showed multiple melting peaks, which can be attributed to lamellar thickness changes upon heating. The crystallite sizes L₁₀₀ and L₀₁₀ of Nylon 66, determined by WAXD, decreased with increasing MWNT contents. Isothermal DSC results showed that crystallization kinetics increased first and then decreased with increasing MWNT contents in Nylon 66. This study showed that the effect of MWNTs on Nylon 66 crystallization is twofold: MWNTs provide heterogeneous nucleation sites for Nylon 66 crystallization while the tube network structure hinders large crystal growth.     

Mechanical,thermal and electrical properties of multi‐walled carbon nanotube/aluminium nitride/polyetherimide nanocomposites

A series of polyimide‐based nanocomposites containing polyimide‐grafted multi‐walled carbon nanotubes (PI‐g MWCNTs) and silane‐modified ceramic (aluminium nitride (AlN)) were prepared. The mechanical, thermal and electrical properties of hybrid PI‐g MWCNT/AlN/polyetherimide nanocomposites were investigated. After polyimide grafting modification, the PI‐g MWCNTs showed good dispersion and wettability in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The utilization of the hybrid filler was found to be effective in increasing the thermal conductivity of the composites due to the enhanced connectivity due to the high‐aspect‐ratio MWCNT filler. The use of spherical AlN filler and PI‐g MWCNT filler resulted in composite materials with enhanced thermal conductivity and low coefficient of thermal expansion. Results indicated that the hybrid PI‐g MWCNT and AlN fillers incorporated into the polyetherimide matrix enhanced significantly the thermal stability, thermal conductivity and mechanical properties of the matrix. Copyright © 2012 Society of Chemical Industry     

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     

Nanotube surface functionalization effects in blended multiwalled carbon nanotube/PVDF composites

A mixed fill system of multiwalled carbon nanotubes (MWCNT) and hydroxylated MWCNT (HO‐MWCNT) in a poly(vinylidene fluoride) (PVDF) matrix was investigated to improve nanotube dispersion and enhance electrical percolation for the bulk nanocomposites. Nonfunctionalized MWCNT were blended at various concentrations into dimethylformamide solutions containing PVDF with 0, 5, or 10 wt % HO‐MWCNT. Composite samples prepared from these solutions were examined by four‐point probe resistivity measurements. The percolation threshold decreased from 0.49 wt % MWCNT in binary MWCNT/PVDF composites to 0.25 wt % for ternary composites containing MWCNT/HO‐MWCNT/PVDF, with either 5 or 10 wt % HO‐MWCNT. In the case of the ternary composite with 10 wt % HO‐MWCNT, the lowest fill percent of MWCNT (0.25 wt %) measured a conductivity that was three orders of magnitude higher than the binary MWCNT/PVDF composite containing twice the concentration of MWCNT (0.5 wt %). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011