Phr Multi-walled Carbon Nanotubes Research Articles

Studies on toughened polycarbonate/multiwalled carbon nanotubes nanocomposites

The electrically conducting nanocomposites (NCs) of toughened polycarbonate (PC) fabricated by using melt blending method with different loadings of multiwalled carbon nanotube (MWCNTs) ranging from 0.25 to 10 phr were studied in this paper. Thus prepared NCs were characterized for morphology (scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction), mechanical properties, thermal property, electrical conductivity (using two probe method) and electromagnetic interference shielding effectiveness (using vector network analyzer). The impact strength of toughened PC prepared by blending PC with 5 wt% of ethylene methyl acrylate (EMA) copolymer having impact strength 318 J/m i.e. 381% improvement as compared to neat PC was further increased to 19% (378 J/m) after 1 phr addition of MWCNTs. Maximum tensile strength and modulus of PC/EMA-MWCNT NCs (about 39 and 60% increase respectively as compare to PC/EMA blend) was achieved at the loading of 10 phr MWCNT. An electrical percolation threshold (pc) occurred at 1 phr of MWCNTs and higher electrical conductivity value about 1.56 × 10−3 S cm−1 was attained for PC/EMA (95/5) having 10 phr of MWCNTs. Maximum EMI shielding effectiveness of toughened PC having 10 phr of MWCNTs was observed as ∼ −26 dB in X-band with samples of 3 mm thickness.

Synergistic effects of hybridization of carbon black and carbon nanotubes on the mechanical properties and thermal conductivity of a rubber blend system

Abstract The effects of hybridization of multi-walled carbon nanotubes (MWCNTs) with carbon black (CB) and the structure-property relationships of nanocomposites based on hydrogenated nitrile-butadiene rubber/hydrogenated carboxylated nitrile-butadiene rubber blends were extensively studied. MWCNTs used in this work were modified through acid treatment to improve the dispersion of MWCNTs in the rubber matrix and the surface interaction between MWCNTs and matrix. Synergistic interaction between CB and MWCNTs increased the tensile modulus and tear strength of nanocomposites. The effect of MWCNTs on the transport properties invoked an increment in the thermal conductivity of the nanocomposites. A combination of 10 phr (parts per hundred rubber) MWCNTs with 40 phr CB dramatically increased the modulus at 100% elongation, tear strength, and thermal conductivity of the nanocomposite by 66%, 28%, and 36%, respectively, compared with those of nanocomposite filled with 40 phr CB.

Improved shape memory effects in multiwalled‐carbon‐nano‐tube reinforced thermosetting polyurethane composites

ABSTRACTShape memory thermosetting polyurethane (SMPU) composites containing different amount of multiwalled carbon nanotube (MWCNT) ranging from 0 to 0.250 phr were prepared. The shape memory behavior, tensile stress, and recovery stress were determined by using conventional thermomechanical cycle; however, the modified thermomechanical cycle designated as progressive stretch–relax–stretch (PSRS) cycle was also employed to create shape memory effects in studied composites. The test was carried out in water bath which was equipped with an electric heater, temperature controller, and tensile stress and strain measuring setup. The recovery and tensile stresses both were showing higher values for PSRS samples as compared with conventional samples. Loading of MWCNT improved the recovery stress of SMPU, thereby confirming reinforcing effect. The maximum recovery stress of 2.17 MPa for 0.188 phr MWCNT loading was observed as compared with 1.09 MPa of unreinforced SMPU specimen. The recovery time was also improved on reinforcement as demonstrated in this article. The morphology of fractured surface and degree of dispersion of MWCNT was studied using Field Emission Scanning Electron Microscope. The impact on glass transition temperature was also observed for MWCNT reinforcement on SMPU, which depends on the degree of dispersion and loading of MWCNT in the specimen. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44389.

Mechanical properties, thermal behaviors and oil resistance of epoxidized natural rubber/multiwalled carbon nanotube nanocomposites prepared via in situ epoxidation

Epoxidized natural rubber (ENR)/multiwalled carbon nanotube (MWCNT) nanocomposites were prepared via in situ epoxidation of natural rubber (NR) using a molar ratio of formic acid/hydrogen peroxide to isoprene unit at 0.75/0.75 with five loadings of MWCNTs, ranging from 0.5–2.5 parts per hundred parts of rubber (phr), at 50°C for 4 h. Based on Fourier transform infrared spectra, the epoxide content of ENR in the nanocomposites was about 32.5–33.2 mole%. Accordingly, the products were referred to ENR30/MWCNT nanocomposites. The curing characteristics, mechanical properties (tensile properties, tear strength, and hardness), glass transition temperature ( Tg), thermal stability, and oil resistance of these in situ ENR30/MWCNT nanocomposites were investigated and compared with NR and neat ENR30. The results showed that the scorch and cure times of ENR30/MWCNT nanocomposites were the longest followed by NR and ENR30. The incorporation of an appropriate amount of MWCNTs into the in situ epoxidation apparently improved the properties of NR. Among them, the nanocomposites filled with 2 phr MWCNTs exhibited the highest mechanical properties, Tg, thermal stability, and oil resistance. The mechanical properties of the in situ nanocomposites were also compared with those of the control nanocomposites prepared by adding MWCNTs directly in the prepared ENR30 latex. It was found that at similar MWCNT loadings, the in situ nanocomposites exhibited higher mechanical properties than the control nanocomposites.

Effect of annealing at room temperature on the surface resistivity of elastomer/multiwalled carbon nanotube nanocomposites

In this study, thermoplastic polyurethane (TPU) and ethylene propylene diene terpolymer (EPDM) were melt‐mixed with multi walled carbon nanotube (MWCNT), respectively. The change in the surface resistivity of the nanocomposites during annealing at room temperature was examined. The surface resistivity of TPU/MWCNT nanocomposites with 3 and 5 phr MWCNT and uncrosslinked EPDM/MWCNT nanocomposites with 4 and 6 phr MWCNT significantly increases with increasing annealing time at room temperature. To delay the increase of surface resistivity during annealing at room temperature, silica was added to the TPU/MWCNT and EPDM/MWCNT nanocomposites. The rate of increase in the surface resistivity during annealing at room temperature was much slower with addition of silica to the nanocomposites. POLYM. COMPOS., 38:E525–E530, 2017. © 2016 Society of Plastics Engineers

Multiwalled carbon nanotubes and fluoroelastomer antistatic nanocomposite for automotive fuel system components

Fluoroelastomer (FKM) composites, reinforced with multiwalled carbon nanotubes (MWNTs), were prepared by conventional method to determine the possibility of using MWNTs to develop an antistatic composite in automotive fuel systems. The results obtained from the composite containing 0-9 phr of MWNTs were compared. A 5 points increase in hardness was achieved with the addition of only 1 phr of MWNTs and 9 phr added FKM composite was increased 6.4MPa in tensile strength compared to the MWNTs unfilled FKM composite. In addition, electrical conductivity increased from 0 to 1.039 Scm−1 with increase in the MWNTs concentration, and the dynamic damping property was increased in the rubbery state region accordingly. These phenomena can be explained by the MWNTs networks formed in FKM matrix. This research will therefore be useful in the development of an antistatic rubber composite for fuel system components, which are deformed or vibrated while in operation.

Property improvement of room temperature vulcanized silicone elastomer by surface-modified multi-walled carbon nanotube inclusion

Room temperature vulcanized (RTV) silicone rubber composites reinforced by multi-walled carbon nanotubes (MWCNTs) were prepared. The effect of surface modification methods and MWCNT contents on the properties of the RTV silicone rubber composites was investigated. The properties of the composites were improved when the treated MWCNTs were used. After treated by polyester-modified polydimethylsiloxane solution (BKY-310), the MWCNTs were uniformly dispersed in the silicone rubber matrix. When 5 phr of MWCNTs was added, the composite achieved good comprehensive performance. Its tensile strength, tear strength, elongation and onset decomposition temperature reach 2.0 MPa, 11.7 kN/m, 238% and 510 °C, respectively. But the above said values for the composite with untreated MWCNTs are only 1.1 MPa, 7.0 kN/m, 83% and 484 °C, respectively.

Comparison of PVDF/MWNT, PMMA/MWNT, and PVDF/PMMA/MWNT nanocomposites: MWNT dispersibility and thermal and rheological properties

Pristine multi-walled carbon nanotubes (MWNTs) were incorporated into poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA), and PVDF/PMMA blends to achieve binary and ternary nanocomposites. MWNTs were more compatible with the PVDF matrix than with the PMMA-containing matrices. MWNT addition did not alter the development of α-form PVDF crystals in the binary/ternary composites. Nucleation and overall isothermal crystallization of PVDF were enhanced by the presence of MWNTs, and enhancements were optimal in the PVDF/MWNT binary composites. Avrami analysis revealed that addition of MWNTs led to more extensive athermal-type nucleation of PVDF, and that PMMA slightly decreased the crystal growth dimension of PVDF. The equilibrium melting temperature (Tm°) of PVDF increased in the binary composites but remained nearly constant in the ternary system. Thermal stability was enhanced in the binary/ternary composites, and enhancements were more evident in the air environment than in nitrogen. Rheological property measurements revealed that the intensely entangled chains of high-molecular weight PVDF dominated the rheological response of PVDF-included samples in the melt state. A (pseudo)network structure was developed in each of the PVDF-included samples as well as in the 1 phr MWNT-added PMMA/MWNT composite. The storage moduli of the PVDF, PMMA, and PVDF/PMMA:1/1 blend increased to 37%, 22% and 34%, respectively, at 40 °C after addition of 1 phr MWNT.

Structural and Dielectric Studies of MWCNT Reinforced Microcellular Silicone Elastomer Nanocomposite

Microcellular silicone rubber nanocomposites, filled with 2 phr multi-walled carbon nanotubes (MWCNTs), were prepared by a two roll mixing mill with different blowing agent concentrations. The distribution of the conductive nanoparticles has been investigated with scanning electron microscopy (SEM). The FTIR spectra of nanocomposites have been studied in the range of 500-4000cm-1 and their corresponding peaks have been assigned. The effect of MWCNT on dielectric properties of microcellular silicone elestomer nanocomposites were studied in the frequency range of 100 Hz–5MHz to understand the electrical conduction mechanism.

Improved recovery stress in multi-walled-carbon-nanotubes reinforced polyurethane

The shape-recovery performance of multi-walled-carbon-nanotubes (MWCNT) reinforced shape-memory-thermoplastic-polyurethane (SMTPU) was investigated for modified Shape-Memory-Creation-Procedure (SMCP). The modified SMCP replaced the conventional stretching scheme of deformation which is generally employed to attain temporary-shape. A Progressive-Stretch-Relax-Stretch (PSRS) scheme of deformation was introduced to create temporary shape in SMTPU and MWCNT-SMTPU nanocomposites. As compared to the conventional deformation, PSRS deformation exhibited more than 50% increase in the recovery-stress in all the composites. The cast-films of SMTPU having 0, 1, 2, 3 and 5 phr MWCNT were prepared. Significant improvement in recovery-stresses was also observed with the increased content of MWCNT. DSC studies revealed increased glass-transition temperature with MWCNT content. These composites exhibited higher values of shape-fixity with increased content of MWCNT. The samples prepared under PSRS scheme, having 5 phr MWCNT in SMTPU, attained high recovery stress 6.95MPa as compared to 3.68MPa with conventional method at 780% strain of the sample.

Effect of processing parameters on the surface resistivity of ethylene propylene diene terpolymer/multiwalled carbon nanotube nanocomposites

ABSTRACTIn this study, ethylene propylene diene terpolymer (EPDM) is melt‐mixed with multiwalled carbon nanotube (MWCNT). To realize full‐scale application of MWCNT to the rubber industries, the effect of melt‐processing parameters on the surface resistivity in the rubber/MWCNT nanocomposites should be well understood. The effect of rotor speed, mixing temperature, and annealing time on the surface resistivity of the EPDM/MWCNT nanocomposites has been investigated. The surface resistivity of EPDM/MWCNT nanocomposites with 3 phr MWCNT increases with increasing the rotor speed and decreasing the mixing temperature. Tensile strength and tensile modulus of EPDM/MWCNT (3 phr) nanocomposites are higher than those of EPDM, respectively. For the nanocomposite with 3 phr MWCNT loadings, surface resistivity increases as the annealing time at room temperature increases. This is the first report that surface resistivity of rubber/MWCNT nanocomposites increases significantly on annealing at room temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40129.

The Effect of Natural Rubber Toughening on Mechanical Properties of Poly(lactic Acid)/Multiwalled Carbon Nanotube Nanocomposite

nvestigation was done on the use of natural rubber (NR) as impact modifier in polylactic acid (PLA) nanocomposite containing carboxylic functionalized multiwalled carbon nanotubes (MWCNT) as nanofillers. NR toughened PLA nancomposite consisting of 1 phr MWCNT and NR contents varies from 5 to 20 wt% were prepared by direct melt blending in a counter-rotating twin-screw extruder followed by injection moulding into test specimens for mechanical properties analysis. The tensile, flexural and impact test analysis were carried out to investigate the mechanical properties of PLA/NR/MWCNT nanocomposites at different loading of NR. As comparison, pure PLA, PLA/NR with 5 wt% NR and PLA/MWCNT with 1 phr nanotubes were also prepared with similar method. Results indicated that introduction of NR into PLA/MWCNT contributed to significant improvement in impact strength and ductility of the nanocomposite. Moreover, the deterioration effect of nancomposites stiffness, mechanical and flexural strength due to the introduction of NR was minimized with the presence of MWCNT in the nanocomposite system.

Relaxation behavior of chlorobutyl elastomer nanocomposites: effect of temperature, multiwalled carbon nanotube and frequency

Dynamic mechanical (visco-elastic) relaxation and dielectric relaxation spectra of multiwalled carbon nanotube (MWCNT) reinforced chlorobutyl (CIIR) elastomer nanocomposites were studied. The primary relaxation (α transition, the glass transition) have been studied by dynamic mechanical analysis as a function of temperature (−100 °C to 100 °C) at a frequency of 1 Hz and at 1 % strain. Irrespective of the MWCNT loading, all nanocomposites showed glass-transition temperatures in the range of −15 °C to −10 °C, which was explained on the basis of the relaxation dynamics of polyisobutylene chains in the vicinity of the fillers. The nonlinearity in the tan δ and storage modulus was explained by the concept of MWCNT-chlorobutyl interactions and the aggregation of the nanotubes. The secondary relaxation (α* or β relaxation) have been studied using dielectric relaxation spectra in the frequency range of 100–106 Hz. The capacitance of the nanocomposite was expressed in terms of dielectric permittivity and explained on the basis of polarization of the MWCNT in the chlorobutyl matrix. The electric modulus formalism has been utilized to further investigate the conductivity and relaxation phenomenon. Argand diagram confirms the existence of non-debye/non-linear relationship. The percolation threshold of was found to be at 6 phr MWCNT loading, as studied by conductivity and dielectric permittivity measurements.

Interfacial localization of multiwalled carbon nanotubes in immiscible blend of poly(ethylene terephthalate)/polyamide 6

In this study, multiwalled carbon nanotubes (MWCNTs) were confined or localized in an immiscible blend of poly(ethylene terephthalate)/polyamide 6 (PET/PA6). A co-rotating twin-screw extruder and melt-compounding were used to prepare nanocomposites of PET/PA6 (60/40, w/w) and MWCNTs with various MWCNT contents in the range 0.001–2 phr. The raw, unfunctionalized MWCNTs were used as fillers. A remarkable change in the morphology of the blend happened on the basis of the amount of MWCNTs added to the blend: the PET phase converted into the PA6 phase at a certain MWCNT content. Although the PA6 phase was formed as a domain phase in the PET matrix in blends containing less than 0.01 phr of MWCNTs, the PET phase suddenly became discontinuous because of phase conversion in the PA6 matrix in blends containing 0.01 and 0.05 phr of MWCNTs. In the blends containing more than 0.1 phr of MWCNTs, the initial morphology was recovered, that is, the PET phase became the matrix phase again. Moreover, in the recovered state, the of the PA6 domain was much larger in the blends containing more than 0.1 phr of MWCNTs than it was in the composites that did not contain any MWCNTs and in those that contained 0.001 phr of MWCNTs. The MWCNTs, on the other hand, selectively located at the interface of the PET and PA6 phases. The rheological, electrical, and crystallization behaviors of the blends were also investigated to study the effects of the concentration of MWCNTs on the structure of the prepared composites.

Effects of silica/multiwall carbon nanotube hybrid fillers on the properties of natural rubber nanocomposites

AbstractIn this study, multiwalled carbon nanotubes (MWCNTs) and silica were used as hybrid fillers in natural rubber (NR) nanocomposites. The addition of MWCNTs and silica to NR was varied with the total filler loading fixed at 30 phr. The curing characteristics and mechanical, thermal, and morphological properties were investigated in this study. The results show that the scorch and curing time decreased as the MWCNT loading increased in the silica/MWCNT hybrid, but the maximum torque was increased by about 35%. The highest tensile strength was achieved at a loading ratio of 29 phr silica/1 phr MWCNTs. As the MWCNT loading increased in the silica/MWCNT hybrid, the tensile strength, elongation at break, and fatigue life decreased. However, the tensile modulus and rubber filler interaction increased. The scanning electron microscopy results show a good dispersion and better interaction between silica and the MWCNTs with the NR matrix at a 29/1 silica/MWCNT loading ratio. As the MWCNT loading ratio increased, the agglomeration of the MWCNTs became dominant and reduced the reinforcing effect of the MWCNTs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Fabrication and characterization of NBR/MWCNT composites by latex technology

AbstractTo 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

Ethylene‐vinyl acetate copolymer/multiwalled carbon nanotube/organoclay nanocomposites

AbstractEthylene‐vinyl acetate copolymer (EVA) was melt‐mixed with multiwalled carbon nanotubes (MWCNTs) and organoclays, and the effects of simultaneous use of organoclays and MWCNTs on the surface resistivity and tensile properties of EVA nanocomposites were investigated. The surface resistivity of EVA/MWCNT nanocomposite with 1 phr of MWCNT is out of our measurement range (above 1012 Ω/square). With increasing content of organoclay from 0 to 3 phr, the surface resistivity of the EVA/MWCNT/organoclay nanocomposites with 1 phr MWCNT remains out of our measurement range. However, the surface resistivity of the nanocomposite decreases to 106 Ω/square with addition of 5 phr organoclay. The tensile properties of EVA/MWCNT/organoclay nanocomposites with 1 phr MWCNT and 5 phr organocaly are similar to those of EVA/MWCNT nanocomposites with 5 phr MWCNT except tensile modulus. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers

Uncross‐linked polypropylene (PP)/ethylene‐propylene‐diene (EPDM)/multi walled carbon nanotube (MWCNT) and dynamically vulcanized PP/EPDM/MWCNT nanocomposites

AbstractIn this study, relatively large amounts of polypropylene (PP), ethylene‐propylene‐diene (EPDM), and multi‐walled carbon nanotube (MWCNT) were melt‐mixed with and without DCP. Dynamically vulcanized PP/EPDM (TPV)/MWCNT nanocomposites were prepared by two methods: the MWCNTs were added either before or after the dynamic vulcanization of the blends. The effects of composition, rotor speed, and dynamic vulcanization on their surface resistivity were investigated. The surface resistivity of uncross‐linked PP/EPDM/MWCNT nanocomposites increases with increasing the content of EPDM. At PP/EPDM (70/30 wt%) nanocomposite with 1.5 phr MWCNT, slightly lower surface resistivity is obtained by increasing the rotor speed during mixing. However, for PP/EPDM (50/50 wt%) and PP/EPDM (30/70 wt%) nanocomposites, surface resistivity decreases with increasing the rotor speed from 30 to 60 rpm. But further increase in rotor speed (90 rpm) leads to an increase of surface resistivity. When the MWCNTs were added after the dynamic vulcanization of the blends, the surface resistivity of TPV70/MWCNTnanocomposite is lower than that of uncross‐linked PP/EPDM/MWCNT nanocomposite. However, when the MWCNTs were added before the dynamic vulcanization of the blends, the surface resistivity of TPV70/MWCNT nanocomposite is >1012 Ω/square. Copyright © 2010 John Wiley & Sons, Ltd.

Reducing resistivity of polyamide-6/multi-walled carbon nanotube composites by adding ultra-fine rubber particles on account of non-volume exclusion effect

The volume resistivity of polyamide-6(PA6)/multi-walled carbon nanotube (MWCNT) composites was found to be further reduced by adding a kind of ultra-fine rubber particle (URP) with average diameter of 150 nm due to non-volume exclusion effect. With the addition of 16 phr URP, the percolation threshold of PA6/MWCNT composites was reduced from 6 phr MWCNTs to 3 phr. Besides, at a constant loading of 4 phr MWCNTs, increase of URP loading led to two changes and a plateau for the volume resistivity of composites. The morphological observations of composites revealed that the decrease of volume resistivity was attributed to both homogenous dispersion and stretching of MWCNTs in PA6. The mechanism on better dispersion and stretching of MWCNTs with the help of URP was also given.

The manufacture and investigation of multi-walled carbon nanotube/polypyrrole/EVA nano-polymeric composites for electromagnetic interference shielding

In this study, the multi-walled carbon nanotube (MWNT)–polypyrrole (PPy) was synthesized by chemical oxidative polymerization using cetyltrimethylammonium bromide (CTAB) as the cationic surfactant. The high electric conductivity of the MWNT–PPy(Cl −) was affirmed by the measurement of 4-point-probe method. Then, the MWNT–PPy(Cl −) was used as conductive fillers and was compounded with ethylene–vinyl acetate (EVA) by blending to form polymeric composite (MWNT–PPy(Cl −)/EVA) that possesses excellent electromagnetic interference shielding (EMI SE). Because of the high conductivity of the MWNT–PPy(Cl −) (29/71 wt.%), the MWNT–PPy(Cl −) would interdict the conductive network in the composites. This polymeric composite material could shield the electromagnetic wave. As the cationic surfactant CTAB was added in the MWNT–PPy(Cl −) chemical oxidative polymerization process, the effect of the surfactant was dispersed, absorbed and attenuated on the MWNT in the chemical oxidative polymerization. For this reason, the EMI SE of the MWNT–PPy(Cl −)/EVA composites had an obvious improvement from 10–15 dB to 45–55 dB. In this investigation, the optimum conductive filler was 75.0 phr PPy(Cl −) coated on 18.0 phr MWNT. The morphology of the composite also presented a uniform conducting network when a lot of MWNT–PPy(Cl −) was added.