Thermal conductivity and dynamic mechanical property of glycidyl methacrylate‐grafted multiwalled carbon nanotube/epoxy composites

The well dispersed multiwalled carbon nanotube (MWCNT)/epoxy composites were prepared by functionalization of the MWCNT surfaces with glycidyl methacrylate (GMA). The morphology and thermal properties of the epoxy nanocomposites were investigated and compared with the surface characteristics of MWCNTs. GMA‐grafted MWCNTs improved the dispersion and interfacial adhesion in epoxy resin, and enhanced the network structure. The storage modulus of 3 phr GMA‐MWCNTs/epoxy composites at 50°C increased from 0.32 GPa to 2.87 GPa (enhanced by 799%) and the increased tanδ from 50.5°C to 61.7°C (increased by 11.2°C) comparing with neat epoxy resin, respectively. Furthermore, the thermal conductivity of 3 phr GMA‐MWCNTs/epoxy composite is increased by 183%, from 0.2042 W/mK (neat epoxy) to 0.5781 W/mK. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Reduction of percolation threshold through double percolation in melt‐blended polycarbonate/acrylonitrile butadiene styrene/multiwall carbon nanotubes elastomer nanocomposites

We demonstrate a method that involves melt blending of polycarbonate (PC) and melt‐blended acrylonitrile butadiene styrene (ABS) with multiwall carbon nanotubes (MWCNTs) to prepare electrically conducting PC/MWCNT nanocomposites at significantly low MWCNT loading. The partial solubility of ABS in PC led to a selective dispersion of the MWCNTs in the ABS phase after melt‐blending PC and ABS. Thus, a sudden rise in electrical conductivity (∼10⁸ orders of magnitude) of the nanocomposites was found at 0.328 vol% of MWCNT, which was explained in terms of double percolation phenomena. By optimizing the ratio of PC and the ABS–MWCNT mixture, an electrical conductivity of 5.58 × 10⁻⁵ and 7.23 × 10⁻³ S cm⁻¹ was achieved in the nanocomposites with MWCNT loading as low as 0.458 and 1.188 vol%, respectively. Transmission electron microscopy revealed a good dispersion and distribution of the MWCNTs in the ABS phase, leading to the formation of continuous MWCNT network structure throughout the matrix even at very low MWCNT loading. Storage modulus and thermal stability of the PC were also increased by the presence of a small amount of MWCNTs in the nanocomposites.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Preparation, crystallization, electrical conductivity and thermal stability of syndiotactic polystyrene/carbon nanotube composites

A homogeneous dispersion of multi-walled carbon nanotubes (MWCNTs) in syndiotactic polystyrene (sPS) is obtained by a simple solution dispersion procedure. MWCNTs were dispersed in N-methyl-2-pyrrolidinone (NMP), and sPS/MWCNT composites are prepared by mixing sPS/NMP solution with MWCNT/NMP dispersion. The composite structure is characterized by scanning electron microscopy and transmission electron microscopy. The effect of MWCNTs on sPS crystallization and the composite properties are studied. The presence of MWCNTs increases the sPS crystallization temperature, broadens the crystallite size distribution and favors the formation of the thermodynamically stable β phase, whereas it has little effect on the sPS γ to α phase transition during heating. By adding only 1.0 wt.% pristine MWCNTs, the increase in the onset degradation temperature of the composite can reach 20 °C. The electrical conductivity is increased from 10^{−10∼−16} (neat sPS) to 0.135 S m⁻¹ (sPS/MWCNT composite with 3.0 wt.% MWCNT content). Our findings provide a simple and effective method for carbon nanotube dispersion in polymer matrix with dramatically increased electrical conductivity and thermal stability.     

Graphene nanoplate and multiwall carbon nanotube–embedded polycarbonate hybrid composites: High electromagnetic interference shielding with low percolation threshold

This study has reported the preparation of polycarbonate (PC)/graphene nanoplate (GNP)/multiwall carbon nanotube (MWCNT) hybrid composite by simple melt mixing method of PC with GNP and MWCNT at 330°C above the processing temperature of the PC (processing temperature is 280°C) followed by compression molding. Through optimizing the ratio of (GNP/MWCNT) in the composites, high electromagnetic interference shielding effectiveness (EMI SE) value (∼21.6 dB) was achieved at low (4 wt%) loading of (GNP/MWCNT) and electrical conductivity of ≈6.84 × 10⁻⁵ S.cm⁻¹ was achieved at 0.3 wt% (GNP/MWCNT) loading with low percolation threshold (≈0.072 wt%). The high temperature melt mixing of PC with nanofillers lowers the melt viscosity of the PC that has helped for better dispersion of the GNPs and MWCNTs in the PC matrix and plays a key factor for achieving high EMI shielding value and high electrical conductivity with low percolation threshold than ever reported in PC/MWCNT or PC/graphene composites. With this method, the formation of continuous conducting interconnected GNP‐CNT‐GNP or CNT‐GNP‐CNT network structure in the matrix polymer and strong π–π interaction between the electron rich phenyl rings and oxygen atom of PC chain, GNP, and MWCNT could be possible throughout the composites. POLYM. COMPOS., 37:2058–2069, 2016. © 2015 Society of Plastics Engineers     

Effect of TPU hard segment content on the rheological and mechanical properties of PLA/TPU blends

Blends of an amorphous polylactide (PLA) with three different thermoplastic polyurethane (TPU) grades having various hard segment (HS) contents are prepared at the blending ratio of 85/15 wt% through a twin-screw extruder (TSE) at processing temperatures of 150 and 190°C. Blends of a semicrystalline PLA with 15 wt% of the noted TPU grades are also processed in the TSE at 190°C to investigate the matrix crystallization effect on the morphology and property enhancements. The rheological experiments reveal that the increase in TPU HS content significantly increases the phase compatibility between PLA and TPU as also suggested by the finer morphology of the TPU phase, although the use of lower HS TPUs is more favorable to enhance the ductility and impact properties of the blends.     

Electrical and mechanical tuning of 3D printed photopolymer–MWCNT nanocomposites through in situ dispersion

An electric field-assisted in situ dispersion of multiwall carbon nanotubes (MWCNTs) in polymer nanocomposites, fabricated through stereolithography three-dimensional (3D) printing technique, was demonstrated. The introduction of MWCNTs increased the elasticity modulus of the polymer resin by 77%. Furthermore, the use of an electric field for in situ MWCNT dispersion helped improving the average elongation at break of the samples with MWCNTs by 32%. The electric field also increased the ultimate tensile strength of the MWCNT reinforced nanocomposites by 42%. An increase of over 20% in the ultimate tensile strength of in situ dispersed MWCNT nanocomposites over the pure polymer material was observed. Finally, it was demonstrated that the magnitude and direction of the electrical conductivity of MWCNT nanocomposites can be engineered through the application of in situ electric fields during 3D printing. An increase of 50% in the electrical conductivity was observed when MWCNTs were introduced, while the application of the electric field further improved the electrical conductivity by 26%. The presented results demonstrated the feasibility of tuning both electrical and mechanical properties of MWCNT reinforced polymer nanocomposites using in situ electrical field-assisted 3D printing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47600.     

New approach for distribution of carbon nanotubes in alumina matrix

Alumina–carbon nanotubes composites were studied with respect to obtain the homogeneous distribution of nanotubes within the alumina matrix. Disaggregation and uniform dispersion of carbon nanotubes in alumina matrix are crucial requirements for improvement fracture toughness and also electrical conductivity of these composites. New approach comprises functionalisation MWCNTs by acid treatment, stabilisation of alumina/MWCNT dispersion with subsequent freezing has been used, which resulted in formation of granulated homogenous mixture. The ceramic composites were prepared by hot pressing at 1550 °C using these mixtures. Microstructural analysis as well as electrical conductivity measurements has been used for observation of distribution of nanotubes within composites. Electrical conductivity, as an indicator of homogeneity of conductive network distribution, increases from 6 to 1140 S/m when compared the conventional process and approach presented in this work at the same volume fraction of MWCNTs 10 vol.%.     

Synthesizing multi‐walled carbon nanotube‐polymethyl methacrylate conductive composites and poly(lactic acid) based composites

Multi‐walled carbon nanotube was modified with polymethyl methacrylate (MWCNT‐PMMA) by in situ solution radical polymerization in the presence of 2,2′‐Azobis (isobutyronitrile) as an initiator. The products with different addition of methyl methacrylate (MMA) were pressed into slices to prepare specimens for electrical conductivity testing. It was found that the MWCNT‐PMMA nanocomposites demonstrate excellent electrical conductivity. To investigate the microsphere morphology and the colloidal surfactant of MWCNTs in MWCNT‐PMMA composites, samples were submitted to scanning electron microscopy and transmission electron microscopy. The thermogravimetric analysis of the prepared composites confirmed that MWCNTs as a thermal stabilizer for PMMA, which could have a wide range of potential applications, such as in catalysts, sensors, environmental remediation, and energy storage. Two series of poly(lactic acid) (PLA) based biocomposites with different MMA additions and MWCNT‐PMMA composites contents were prepared with twin‐screw extruding and injection molding. The results show the mechanical properties changed a little with the MMA and MWCNT‐PMMA composites contents increasing, which suggested the well compatibility between MWCNT‐PMMA composites and PLA. POLYM. COMPOS., 37:503–511, 2016. © 2014 Society of Plastics Engineers     

Effect of multiwall carbon nanotubes on thermomechanical and electrical properties of poly(trimethylene terephthalate)

Multiwalled carbon nanotubes (MWCNTs) were synthesized using chemical vapor deposition and poly(trimethylene terephthalate) (PTT)/MWCNT composites with varying amounts of MWCNTs were prepared by melt compounding using DSM micro‐compounder. Morphological characterization by SEM and TEM showed uniform dispersion of MWCNTs in PTT matrix upto 2% (w/w) MWCNT loading. Incorporation of MWCNTs showed no effect on percent crystallinity but affected the crystallite dimensions and increased the crystallization temperature. Dynamic mechanical characterization of composites showed an increase in storage modulus of PTT upon incorporation of MWCNTs above glass transition temperature. The electrical conductivity of PTT/MWCNT composites increased upon incorporation of MWCNTs and percolation threshold concentration was obtained at a loading of MWCNTs in the range of 1–1.5% (w/w). © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Development of electrical conductivity in PP/HDPE/MWCNT nanocomposite by melt mixing at very low loading of MWCNT

A method of developing an electrical conductivity in polypropylene (PP) with a very low loading of multiwalled carbon nanotube (MWCNT) by melt‐mixing method was described. PP/high‐density polyethylene (HDPE; 70/30, w/w) was melt blended simultaneously in the presence of MWCNT using two sequential heating protocol (MWCNT was first interacted with HDPE chain at 140°C followed by melt blending of PP at 200°C). Very interestingly, a cocontinuous morphology in the blend was found even for very high asymmetric composition. This has been explained in terms of barrier effect of the MWCNT dispersed selectively in the HDPE phase that restricts the phase inversion into the matrix droplet morphology. A simple method was used for proper dispersion, distribution, and formation of effective conducting network path [carbon nanotube (CNT)–CNT contact] of MWCNT through cocontinuous HDPE phase (minor phase) into PP matrix of the blend which in turn enhanced the electrical conductivity of the nanocomposite with minimum percolation threshold. The percolation threshold of PP/HDPE/MWCNT nanocomposite found at 0.352 wt% loading of MWCNT, which is significantly lower than those reported for developing electrical conductivity in PP/MWCNT nanocomposite. Phase morphology, extent of dispersion and location of the MWCNT in the blend has been investigated with a scanning and transmission electron microscopy. Thermal and mechanical properties of PP/HDPE/MWCNT nanocomposite with variation of MWCNT loading have also been studied. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Fabrication and characterization of NBR/MWCNT composites by latex technology

To develop a rubber composite with excellent electrical properties, a sort of synthetic rubber, acrylonitrile butadiene rubber (NBR) with CN dipoles as matrix, multi‐walled carbon nanotubes (MWCNTs) as filler, was synthesized. NBR composites reinforced with 0.5, 1.5, 3, 10, and 20 phr MWCNT contents were fabricated by latex technology. The electrical conductivity, dielectric characteristics, and electromagnetic interference (EMI) shielding effectiveness at room temperature of NBR/MWCNT composites were investigated. MWCNTs were found well dispersed into NBR matrix even for 20 phr content by FESEM observation. The electrical conductivity increased with an increment of MWCNT content. The dielectric constant was over 10⁴ at 10³ Hz frequency for 10 and 20 phr MWCNTs‐reinforced NBR composites. It was attributed to the increased electrons and interface polarization. The improved conductivity and dielectric permittivity resulted in an enhanced EMI shielding effectiveness. The EMI shielding effectiveness reached 26 dB at 16.7 GHz frequency for NBR/20 phr MWCNT composite with 1.0 mm thickness. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

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     

Low percolation threshold in polycarbonate/multiwalled carbon nanotubes nanocomposites through melt blending with poly(butylene terephthalate)

Here, we demonstrate an easy method for the preparation of highly electrically conductive polycarbonate (PC)/multiwalled carbon nanotubes (MWCNTs) nanocomposites in the presence of poly(butylene terephthalate) (PBT). In the presence of MWCNTs, PC and PBT formed a miscible blend, and the MWCNTs in the PC matrix were uniformly and homogeneously dispersed after the melt mixing of the PC and PBT–MWCNT mixture. Finally, when the proportion of the PC and PBT–MWCNT mixture in the blend/MWCNT nanocomposites was changed, an electrical conductivity of 6.87 × 10^?7 S/cm was obtained in the PC/PBT–MWCNT nanocomposites at an MWCNT loading as low as about 0.35 wt %. Transmission electron microscopy revealed a regular and homogeneous dispersion and distribution of the MWCNTs and formed a continuous conductive network pathway of MWCNTs throughout the matrix phase. The storage modulus and thermal stability of the PC were also enhanced by the presence of a small amount of MWCNTs in the nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Conductive and flexible multi-walled carbon nanotube/polydimethylsiloxane composites made with naphthalene/toluene mixture

Conventional conductive materials face challenges when utilizing them for flexible and wearable electronics and soft robotics. Carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites are a promising alternative to the conventional hard conductors because they are light and can realize large deformation. To date, well dispersion of CNTs into PDMS to increase conductivity while maintaining flexibility remains challenging. We aimed at developing highly electrically conductive and flexible multi-walled carbon nanotube/PDMS (MWCNT/PDMS) composites. To this end, we proposed a method to enhance the dispersion of MWCNTs into PDMS using naphthalene and toluene. Our results showed that the addition of naphthalene and toluene into the composites improved dispersion of the MWCNTs and increased the direct current (DC) electrical conductivity. We also found that the morphology of primary aggregates of the MWCNTs influenced the DC electrical conductivity of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48167.     

Electrically conductive superhydrophobic octadecylamine-functionalized multiwall carbon nanotube films

Electrically conductive, superhydrophobic multiwall carbon nanotube (MWCNT) thin films were prepared by direct amination of MWCNTs with up to 14 wt.% of octadecylamine (ODA) by vacuum filtration method. The ODA-functionalized MWCNT films exhibit a high water contact angle of 165° and electrical conductivity of 860 S/m. The liquid–air–solid interface is directly observed from above the water droplet using an optical microscope. The observation indicates that the wettability state of the MWCNTs has changed from relatively hydrophilic to superhydrophobic state upon functionalization with ODA. The fundamental mechanisms responsible for the unusual combination of surface superhydrophobicity and high electrical conductivity of the MWCNT films are described and their implications are discussed.     

Effect of compatibilizer on morphology,thermal, and rheological properties of polypropylene/functionalized multi‐walled carbon nanotubes composite

Multi‐walled carbon nanotubes (MWCNTs) filled polypropylene (PP) composites were prepared by a corotating intermeshing twin screw extruder. To improve the dispersion of MWCNTs, the surface of MWCNT was modified with 1,10‐diaminodecane, and maleic anhydride grafted polypropylene (MA‐g‐PP) was used as a compatibilizer. Micrographs of well dispersed functionalized MWCNTs (diamine‐MWCNT) were observed due to the reaction between MA‐g‐PP and diamine‐MWCNT in PP/MA‐g‐PP/diamine‐MWCNTs composites. The different behaviors in crystallization and melting temperatures of PP/MA‐g‐PP/diamine‐MWCNTs composite were observed compared to PP and PP/neat‐MWCNT. Especially, the decomposition temperature of the composite was increased by 50°C compared to PP. PP/MA‐g‐PP/diamine‐MWCNTs composite showed the highest complex viscosity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The role of a biobased epoxy monomer in the preparation of diglycidyl ether of bisphenol A/MWCNT composites

A biobased epoxy monomer (GA‐II) derived from gallic acid for multiwalls carbon nanotubes’ (MWCNTs) dispersion improvement is reported in this article. The aromatic group in its molecular structure made it to be absorbed onto the surface of MWCNTs via π‐π interactions and the GA‐II anchored MWCNT could be homogeneously dispersed in DGEBA matrix via sonication. That was proved by Raman and UV spectroscopy as well as scanning electron microscope. After curing reaction, the epoxy/MWCNT composites demonstrated enhanced mechanical properties, excellent thermal conductivity, and high electrical conductivity. With the addition of only 0.5 wt% GA‐II modified MWCNT, the tensile strength, tensile modulus, flexural strength, and flexural modulus of the composites were improved by 28%, 40%, 22%, and 16%, respectively. The thermal and electrical conductivities were also improved from 0.15 to 0.25 W/m K (67% increased) and from 0.7 × 10⁻¹⁴ to 0.24 × 10⁻⁴ S cm⁻¹ (10 orders increased). POLYM. COMPOS., 38:1640–1645, 2017. © 2015 Society of Plastics Engineers     

Morphology and electrical properties of polymethylmethacrylate/poly(styrene‐co‐acrylonitrile)/multi‐walled carbon nanotube nanocomposites

Nanocomposites of blends of polymethylmethacrylate (PMMA) and poly(styrene‐co‐acrylonitrile) (SAN) with multi‐walled carbon nanotubes (MWCNTs) were prepared by melt mixing in a twin‐screw extruder. The dispersion state of MWCNTs in the matrix polymers was investigated using transmission electron microscopy. Interestingly enough, in most of the nanocomposites, the MWCNTs were observed to be mainly located at SAN domains, regardless of the SAN compositions in the PMMA/SAN blend and of the processing method. One possible reason for this morphology may be the π–π interactions between MWCNTs and the phenyl ring of SAN. The shift in G‐band peak observed in the Raman spectroscopy may be the indirect evidence proving these interactions. The percolation threshold for electrical conductivity of PMMA/SAN/MWCNT nanocomposites was observed to be around 1.5 wt %. Nanocomposites with PMMA‐rich composition showed higher electrical conductivity than SAN‐rich nanocomposites at a fixed MWCNT loading. The dielectric constant measurement also showed composition‐dependent behavior. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrical conductivity behavior of epoxy matrix nanocomposites with simultaneous dispersion of carbon nanotubes and clays

In this work, nanocomposites with simultaneous dispersion of multiwalled carbon nanotubes (MWCNT) and montmorillonite clays in an epoxy matrix were prepared by in situ polymerization. A high energy sonication was employed as the dispersion method, without the aid of solvents in the process. The simultaneous dispersion of clays with carbon nanotubes (CNT) in different polymeric matrices has shown a synergic potential of increasing mechanical properties and electrical conductivity. Two different montmorillonite clays were used: a natural (MMT‐Na⁺) and an organoclay (MMT‐30B). The nanocomposites had their electrical conductivity (σ) and dielectric constant (ε_r) measured by impedance spectroscopy. The sharp increase in electrical conductivity was found between 0.10 and 0.25 wt% of the MWCNTs. Transmission electron microscopy (TEM) of the samples showed a lower tendency of MWCNT segregation on the MMT‐30B clay surface, which is connected to intercalation/exfoliation in the matrix, that generates less free volume available for MWCNTs in the epoxy matrix. Data from electrical measurement showed that simultaneously adding organoclay reduces the electrical conduction in the nanocomposite. Moreover, conductivity and permittivity dispersion in low frequency suggest agglomeration of nanotubes surrounding the natural clay (MMT‐Na⁺) particles, which is confirmed by TEM. POLYM. COMPOS., 37:1603–1611, 2016. © 2014 Society of Plastics Engineers     

Low percolation threshold and high electrical conductivity in melt‐blended polycarbonate/multiwall carbon nanotube nanocomposites in the presence of poly(ε‐caprolactone)

This study focuses on the electrical properties of polycarbonate (PC)/poly(ε‐caprolactone) (PCL)‐multiwall carbon nanotube (MWCNT) nanocomposites. MWCNTs were incorporated into thermoplastic PC matrix by simple melt blending using biodegradable PCL based concentrates with MWCNT loadings (3.5 wt%). Because of the lower interfacial energy between MWCNT and PCL, the nanotubes remain in their excellent dispersion state into matrix polymer. Thus, electrical percolation in PC/PCL‐MWCNT nanocomposites was obtained at lower MWCNT loading rather than direct incorporation of MWCNT into PC matrix. AC and DC electrical conductivity of miscible PC/PCL‐MWCNT nanocomposites were studied in a broad frequency range, 10¹?10⁶ Hz and resulted in low percolation threshold (p_c) of 0.14 wt%, and the critical exponent (t) of 2.09 from the scaling law equation. The plot of logσ_DC versus p^?1/3 showed linear variation and indicated the existence of tunneling conduction among MWCNTs. At low MWCNT loading, the influence of large polymeric gaps between conducting clusters is the reason for the frequency dependent electrical conductivity. Transmission electron microscopy and field emission scanning electron microscopy showed that MWCNTs were homogeneously dispersed and developed a continuous interconnected network path throughout the matrix phase and miscibility behavior of the polymer blend. POLYM. ENG. SCI., 54:646–659, 2014. © 2013 Society of Plastics Engineers