Multi-walled Carbon Nanotubes In Polymer Matrix Research Articles

Electrical conductivity and Vickers hardness enhancement by pristine and functionalized MWCNTs incorporation in polycaprolactam matrix

Several electronic applications have been developed through the use of carbon nanotubes and polymer composites. Multiwalled carbon nanotubes (MWCNTs), functionalized and pristine, were incorporated in polycaprolactam matrix; hydrochloric acid (19 and 38%) and formic acid (88%) were used as polymer solvents. Mechanical stirring method was employed to dissolve the polymer and achieve the dispersion of MWCNTs in polymer matrix. The obtained composites were characterized by scanning electron microscopy, confirming the presence of MWCNTs in polymer. Raman and Fourier transformed infrared spectra were used to identify the interaction between MWCNTs and polycaprolactam. Hardness improvements were proved through microhardness test, reaching values over 100 Hv units. The electrical conductivity in composites with the highest MWCNTs content (4 wt%) was confirmed. The results described in this manuscript confirm the possibility to develop a new material using MWCNTs dispersion in polycaprolactam matrix and possible applications in electronical and mechanical fields.

Achieving excellent dispersion and electrical conductivity of olefin block copolymer/MWCNTs composites efficiently via high-shear processing

Melt blending is a promising and practical method to prepare electrical conductive polymer composites containing multiwalled carbon nanotubes (MWCNTs). The key is to achieve a good dispersion of MWCNTs in polymer matrix. In this study, olefin block copolymer (OBC)/MWCNTs composites were prepared using co-rotating twin-screw extruder with high rotation speed and the influence of screw rotation speed on the dispersion, shortening of MWCNTs and the macro-properties of composites was systematically investigated. It was found that the entangled agglomerates of MWCNTs could be easily destroyed by using high rotation speed and an improved dispersion of MWCNTs was observed as increasing of rotation speed from 50 to 500 rpm. However, with further increasing of rotation speed from 500 to 1000 rpm, no better dispersion was evidenced but a reduction of nanotubes length was detected. As a result, the best electrical conductivity and mechanical properties of OBC/MWCNTs composites were achieved via using the rotation speed of 500 rpm. And the electrical percolation threshold obtained was about 1.5 wt%. This study provides significant guidance for large-scale preparation of conductive composites materials by using co-rotating twin-screw extruder with high rotation speed.

Synergistic effects of two types of ionic liquids on the dispersion of multiwalled carbon nanotubes in ethylene-vinyl acetate elastomer: preparation and characterization of flexible conductive composites

Flexible conductive composites based on an elastomer, ethylene-vinyl acetate copolymer (EVM), and multiwalled carbon nanotubes (MWCNTs) were fabricated by melt-blending and subsequent crosslinking. Two types of ionic liquids, tributylmethylammoniu bis(trifluoromethanesulfonyl)imide and 1-ehtyl-3-methylimidazolium tetrafluoroborate, have been used to modify MWCNTs for the purpose to improve the dispersion of MWCNTs in the polymer matrix. It was found that the MWCNTs modified by the individual IL form agglomerates in the EVM matrix, while the MWCNTs modified by the two types of ILs simultaneously disperse in the EVM matrix homogeneously. Moreover, the nanocomposites based the MWCNTs modified by the combination of the two ILs exhibit improved mechanical and electrical properties. The mechanism of such synergistic effects has been investigated. It was found that EVM is miscible with tributylmethylammoniu bis(trifluoromethanesulfonyl)imide and it is immiscible with 1-ehtyl-3-methylimidazolium tetrafluoroborate. On the other hand, MWCNTs show higher interaction with 1-ehtyl-3-methylimidazolium tetrafluoroborate than tributylmethylammoniu bis(trifluoromethanesulfonyl)imide. Therefore, the uniform dispersion of MWCNTs in EVM matrix is attributed to the “bridging” effects by the two ILs due to the different interactions of the two ILs with MWCNTs and EVM. The application by two types of ILs modified MWCNTs in polymer matrix opens a new fabrication strategy for high performance polymer nanocomposites.

Selective distribution and migration of carbon nanotubes enhanced electrical and mechanical performances in polyolefin elastomers

A thermodynamic and kinetic method based on the selective distribution and migration of multi-walled carbon nanotubes (MWCNTs) in polyoxyethylene (PEO)/ethylene-α-octene random copolymer (ORC) composite system was reported to improve the dispersion of MWCNTs in ORC. Scanning electron micrographs and transmission electron micrographs confirmed that MWCNTs could almost completely migrate from the PEO phase to the ORC phase during melt compounding and lead to tremendously improved dispersion of MWCNTs in ORC, compared with traditional melt compounded ORC/MWCNT composites. Rheological analysis revealed that better MWCNTs network was developed at a lower content of MWCNTs with an improved dispersion of MWCNTs in ORC. The percolation threshold was drastically reduced from 3.82 to 0.35 vol % and the electrical conductivity was tremendously improved. The mechanical properties were also fully enhanced in comparison with traditional melt compounded ORC/MWCNT composites owing to the homogeneous dispersion of MWCNTs. These results manifest that, by proper selection of components with a selective distribution of MWCNTs and controlling the migration process of MWCNTs in the composites, the dispersion of MWCNTs in polymer matrix and resulting performance of the nanocomposites can be greatly improved.

An experimental investigation of surface roughness in the drilling of MWCNT doped carbon/epoxy polymeric composite material

The objective of this research is to investigate the effect of multi-walled carbon nanotube (MWCNT) loading on the surface roughness of drilled hole, in the drilling of MWCNT doped carbon/epoxy polymeric composite material. Root mean square roughness (Rq) was used to assess the effect of MWCNT. Rq was measured at the both side i.e. entrance and exit of hole. Experiment was performed using Box- Behnken Design to develop an empirical model to predict the surface roughness value at the entrance and exit. The developed model was accurate within the level of confidence. Due to loading of MWCNT in polymer matrix, surface roughness of hole at entrance and exit are improved.

Effect of surface functionalization on mechanical properties and decomposition kinetics of high performance polyetherimide/MWCNT nano composites

In this investigation, Polyetherimide (PEI) reinforced with multi-walled carbon nanotube (MWCNT) using novel melt blending technique. Surface of MWCNTs are modified by acid treatment as well as by plasma treatment. PEI nano composites with 2wt% treated MWCNT shows about 15% improvement in mechanical properties when compared to unfilled PEI. The thermal decomposition kinetics of PEI/MWCNT nano composites has been critically analyzed by using Coats – Redfern model. The increase in activation energy for thermal degradation by 699kJ/mol for 2wt% MWCNT implies improvement in the thermal properties of PEI. Studies under Fourier Transform Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM) depict significant interfacial adhesion with uniform dispersion of MWCNT in polymer matrix due to surface functionalization. 0.5wt% chemically modified MWCNT shows typical alignment of MWCNT. There is a significant improvement in mechanical properties and thermal properties for surface functionalized MWCNT reinforced.

Effects of surfactant treatment on mechanical and microwave absorbing properties of graphene nanosheets/multiwalled carbon nanotubes/cyanate ester composites

Graphene nanosheets (GNSs) and multiwalled carbon nanotubes (MWCNTs) were treated with a nonionic surfactant polyvinylpyrrolidone (PVP), and its effects on dispersion state, surface chemistry, structure, and morphology of MWCNTs and GNSs, as well as on the microwave absorbing properties, mechanical properties of GNSs/MWCNTs/cyanate ester nanocomposites were analyzed respectively. Results show that surfactant plays an important role in dispersing the GNSs and MWCNTs in a solvent and polymer. The mechanical properties, such as impact fracture toughness and flexural strength all showed significant improvements after the treatment. The above observations are attributed to the unique amphiphile structures of PVP, which improved the interface characteristic between matrix and the fillers. Besides, PVP can effectively enhance interfacial interactions which gave rise to improved dispersion and wetting of GNSs and MWCNTs in polymer matrix. Unlike chemical functionalization techniques, however, the surfactant treatment exhibited little adverse effect on microwave absorption properties of the nanocomposite. POLYM. COMPOS., 39:110–118, 2018. © 2016 Society of Plastics Engineers

Effect of SiO2 grafted MWCNTs on the mechanical and dielectric properties of PEN composite films

In this study, the functional poly (arylene ether nitrile) (PEN)/multiwall carbon nanotubes (MWCNTs)/SiO2 nanocomposite with high mechanical and good electrical properties were fabricated through a simple and effective method. Specifically, the surface modification using highly ordered and porous SiO2 not only improves the dispersion of the MWCNTs in polymer matrix, but also combines the excellent properties of SiO2 and MWCNTs. Transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR), and scanning electron microscope (SEM) were employed to confirm the surface functionalization of MWCNTs. As a result, all the composite films exhibited good dielectric properties with high dielectric constant of 7 as well as low dielectric loss of 0.04. Besides, the results of mechanical tests showed that the tensile strength and modulus reached their highest values at the 2wt% MWCNTs-SiO2 loading content (125MPa and 2950MPa, respectively). The rheological results showed that MWCNTs-SiO2/PEN composites have a typical solid-like viscoelastic response as frequencies changes. Therefore, all the results revealed that surface functionalization has strong influence on the dispersion state of MWCNTs in PEN matrix.

Radiation resistant metal decorated MWCNTs/PMMA nanocomposite films with enhanced thermomechanical properties

UV/O3 radiation and chemical resistant nanocomposite films of functionalized/metal decorated multiwall carbon nanotubes (MWCNTs) with polymethylmethacrylate (PMMA) are synthesized. Silver nanoparticles are decorated on the surface of UV/O3 functionalized MWCNTs by both reduction and in situ growth from AgNO3 aqueous solution. Microscopic studies reflect the better dispersion of UV/O3 functionalized/silver decorated MWCNTs in polymer matrix contributing in enhancement of thermal stability, thermomechanical strength, glass transition temperatures, and thermal conductivity of nanocomposites even at 0.25 wt% MWCNTs additions. The thermal stability of nanocomposite film (0.25 wt% loading), prepared by using a surfactant (Sodium dodecyl sulfate) is increased to about 27 � C while the thermomechanical properties are raised up to 76% at 100 � C. Thermal and thermomechanical behavior of pre- and post-UV/O3 irradiated nanocomposite films are compared with neat polymer. The results reveal that UV/O3 functionalized MWCNTs can effectively disperse the radiation and have a dramatic reinforcement effect on the nature of the degradation of PMMA matrix. POLYM. COMPOS., 00:000–000, 2014. V C 2014 Society of Plastics Engineers

Synthesis and Physicochemical Behaviour of Polyurethane‐Multiwalled Carbon Nanotubes Nanocomposites Based on Renewable Castor Oil Polyols

Polyurethanes (PUs) are high performance materials, with vast industrial and engineering applications. In this research, effects of Multiwalled Carbon Nanotubes (MWCNTs) on physicochemical properties of Castor Oil based Polyurethanes (COPUs) were studied. MWCNTs were added in different weight percentages (0% to 1% wt) in a castor oil based polyurethane (COPUs‐MWCNTs) nanocomposites. The composition, structure, and morphology of polyurethanes were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), and element detection by energy dispersive spectroscopy (EDX) analysis, respectively. Thermal stability was studied by thermogravimetric analysis (TGA). Barrier properties and surface area studies were investigated by nitrogen permeability machine and BET technique. Mechanical properties were calculated by tensile universal testing machine. Results showed well dispersed MWCNTs in polyurethane matrix at different weight percentages. The best results were obtained with 0.3 wt% of MWCNTs in the composite. Surface area studies revealed presence of very few pores which is in a good agreement with barrier permeability, reduced up to ~68% in 1 wt% and ~70% in 0.5 wt% of MWCNTs in polymer matrix, with respect to pure COPUs samples.

Thermal and thermomechanical behavior of amino functionalized and metal decorated MWCNTs/PMMA nanocomposite films

The homogeneous nanocomposites (NC) films of amino modified and metal decorated multiwall carbon nanotubes (MWCNTs) with polymethylmethacrylate (PMMA) were synthesized through in‐situ free radical polymerization. Silver metal nanohybrids (Ag/MWCNTs) were prepared by two strategies, that is, reduction of metal salt in presence of sodium dodecyl sulfate and in‐situ growth from AgNO3 aqueous solution. The amino functionalization by ball milling enhanced the dispersion of MWCNT in monomer and produced a new class of radiation resistant NC. These synthesized films were characterized by FTIR, TGA, TEM, EDX, TC, DMA, and optical microscopy to ascertain their structural morphologies, thermal stability, and mechanical strength. Microscopic studies reflect the homogeneous mixing of amino functionalized and metal decorated MWCNTs in polymer matrix contributing in the enhancement of thermal stability, thermo‐mechanical strength, glass transition temperatures, and thermal conductivity of NC even at 0.25 wt% addition of modified nanofiller. The thermal stability of NC film at 0.25 wt% loading was increased around ≂50°C and the raise of thermo‐mechanical properties was observed up to 85% at 100°C in the presence of adsorbed surfactant. Thermal and thermomechanical behavior of pre and post UV/O3 irradiated NC films has been compared with neat polymer. The results revealed that amino modified nanofiller embedded network in polymer matrix can effectively disperse the radiation and has a dramatic reinforcement effect on the nature of degradation of PMMA matrix. POLYM. COMPOS., 35:1807–1817, 2014. © 2013 Society of Plastics Engineers

Functionalized carbon nanotubes with oligomeric intumescent flame retardant for reducing the agglomeration and flammability of poly(ethylene vinyl acetate) nanocomposites

AbstractA novel oligomeric phosphorous–nitrogen‐containing intumescent flame retardant poly (2,6‐diaminopyridine spirocyclic pentaerythritol bisphosphonate) (PDSPB) is synthesized, and subsequently multiwalled carbon nanotube (MWNT)‐grafted oligomeric intumescent flame retardant, MWNT‐g‐PDSPB, is fabricated via chemical grafting reaction and characterized. The grafting reaction was characterized by FTIR, NMR, and XPS. After high‐density PDSPB (88 wt%) were attached to the MWNTs, core‐shell nanostructures with MWNTs as the hard core and PDSPB as the soft shell were formed. The resultant MWNT‐g‐PDSPB was soluble and stable in polar solvents, such as DMF and DMSO. MWNT‐g‐PDSPB has excellent thermal stability and charring ability. The TEM results showed that the functionalized MWNTs could achieve better dispersion in poly(ethylene vinyl acetate) (EVA) matrix. The residue char of MWNT‐g‐PDSPB is as high as 70 wt%, and the grafting of intumescent flame retardant of PDSPB can improve both the dispersion of MWNTs in polymer matrix and flame retardancy of the nanocomposites. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers

Effect of processing parameters on the surface resistivity of ethylene–vinyl acetate copolymer/multiwalled carbon nanotube nanocomposites

AbstractIn this study, ethylene–vinyl acetate (EVA) copolymer was melt‐mixed with multiwalled carbon nanotube (MWCNT). To realize full‐scale application of MWCNT to the polymer industries, the effect of melt‐processing parameters on the surface resistivity in the polymer/MWCNT nanocomposites should be well‐understood. The effect of mixing time, rotor speed, compression molding time, and temperature on the surface resistivity was investigated. Increasing the rotor speed and longer mixing time lead to an improvement of dispersion of MWCNT in polymer matrix, resulting in a decrease of surface resistivity. The surface resistivity of EVA/MWCNT nanocomposites is also sensitive to the press temperature and time. However, the dominant processing parameters to affect surface resistivity depend on the amount of MWCNT. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Advance polymeric carbon nanocomposite films with enhanced thermo-mechanical properties

The homogenous nanocomposite films of UV/O3 oxidized multiwall carbon nanotubes (MWCNTs) subsequently modified with aniline moiety were synthesized with polymethylmethacrylate (PMMA) through free radical polymerization. The phenylamine functional groups present on the surface of MWCNTs providing an anchoring sites for deposition of Ag metal nanoparticles (NP).The in situ free radical polymerization of MMA in the presence of these well dispersed nanotubes gave a new class of radiation resistant nanocomposite films. The synthesized materials were characterized by FT-IR, TGA, TEM, EDX, TC, DMA, universal testing machine, and optical microscopy to ascertain their structural morphologies, thermal stability, and mechanical strength. The microscopic and structural properties reflect the homogenous mixing of modified MWCNTs in polymer matrix contributing in enhancement of thermal stability, thermo-mechanical strength, glass transition temperatures, and thermal conductivity of nanocomposites even at 0.25 wt% addition of modified nanofiller. Thermal and thermo-mechanical behavior of pre- and post-UV/O3 irradiated nanocomposite films have been compared with neat polymer. The results revealed that modified nanofiller network can effectively disperse the radiation and has a dramatic reinforcement effect on the nature of degradation of PMMA matrix. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Thermal Properties of Poly(ε-Caprolactone)/Multiwalled Carbon Nanotubes Composites

In this study, multiwalled carbon nanotubes (MWCNTs) were compounded with the poly(ε-caprolactone) (PCL) matrix at the solution state using chloroform. For homogeneous dispersion of MWCNTs in polymer matrix, oxygen-containing groups were introduced on the surface of MWCNTs. The mechanical properties of the PCL/MWCNTs composites were effectively increased due to the incorporation of MWCNTs. The composites were characterized using scanning electron microscopy in order to obtain information on the dispersion of MWCNT in the polymeric matrix. In case of 1.2 wt% of MWCNTs in the matrix, strength and modulus of the composite increased by 12.1% and 164.3%, respectively. In addition, the dispersion of MWCNTs in the PCL matrix resulted in substantial decrease of the electrical resistivity of the composites as the MWCNTs loading was increased from 0 to 2.0 wt%. Furthermore, thermal stability of the PCL and PCL/MWCNTs-COOH composites were investigated using the data acquired from the thermogravimetric analysis. The detailed kinetics of the thermal degradation of the composites was investigated by analyzing their thermal behavior at different heating rates in a nitrogen atmosphere. Activation energy of thermal degradation was determined by using the equations proposed by Kissinger and Flynn–Wall–Ozawa. The apparent activation energy of PCL/MWCNTs-COOH composite was considerably higher than that of neat PCL.