Electrical Properties Of Composites Research Articles

Effects of size and shape originated synergism of carbon nano fillers on the electrical and mechanical properties of conductive polymer composites

ABSTRACTIn this study, microstructural features, mechanical properties, and electrical conductivity behaviors of thermoplastic composites prepared by using of cyclic olefin copolymer (COC) as matrix and various types of carbon nano materials, expanded graphite (EG), carbon nanofiber (CNF), and multi walled carbon nanotubes (CNT) as conductive fillers were investigated. Effects of using of double and triple filler combinations on the electrical properties of composites were also quantified in detail by measuring the bulk resistance of samples under alternating current with an impedance spectrometer. The electrical percolation values of fillers were found to be 20, 10, and 5 phr for the series of composites prepared with the EG, CNF, and CNT, respectively. It was obtained that the bulk resistances of percolated samples were dramatically decreased from 1014 ohm.cm to 103−104 ohm.cm. On the other hand, it was also found that the using of double and triple filler combinations provided much lower (about 101 ohm.cm) bulk resistance which corresponded to higher conductivity values than the highly filled composites including of 30 and 40 phr of EG. Based on the DMA measurements and the quantifying of elastic modulus values of composites in the rubbery region, it was found that the reinforcing effects of carbon nano fillers on the elastic modulus of composites decreased in the order of CNT>CNF>EG, depending on the aspect ratio (Af) values of fillers into the matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42313.

Fracture resistance, thermal and electrical properties of epoxy composites containing aligned carbon nanotubes by low magnetic field

Abstract The alignment of carbon nanotubes (CNTs) with residual catalyst Ni particles in epoxy resin (EP) was achieved under a low magnetic field of 0.4 T. EP composites containing different loading of CNTs were prepared at 60 °C based on the rheology results of CNT/EP suspensions. The effects of CNT loading and magnetic field on the fracture toughness (KIC), glass transition temperature (Tg) and electrical properties of the composites were studied. The obtained results showed significant enhancements in KIC, independent of the orientation of the CNTs, compared to neat epoxy. The maximum increase (∼51%) was achieved by composites with 3 wt.% aligned CNTs transverse to crack growth. Additionally, composites with magnetically aligned CNTs displayed anisotropy in KIC. Compared to CNT/EP composites with no applied magnetic field, the KIC increase was less effective at high CNT loading. Finally, toughening mechanisms, Tg and electrical conductivity results were discussed.

Effects of carbon nanotube content on the mechanical and electrical properties of epoxy-based composites

The effects of multi-wall carbon nanotube (MWCNT) content on the mechanical and electrical properties of MWCNT/epoxy composites were investigated. Results indicate that both tensile strength and flexural modulus exhibit maxima at MWCNT contents of 0.1% and 0.25% (mass fraction), respectively. The tensile modulus increases and the strain to failuredecreases with MWCNT content, indicating a transition from plastic to brittle failure with increasing MWCNT content. The flexural strength of a sample with a MWCNT content of 0.05% is the highest. The electrical percolation threshold of the composite is found to occur at a 0.5% MWCNT addition. A good dispersion of MWCNTs in epoxy is important to improve the mechanical properties of the composites. A non-uniform dispersion leads to agglomeration of MWCNTs, which causes an early-stage failure under loading. The electrical properties of the composites are less affected by the presence of agglomerates.

SWCNT/에폭시 복합체의 기계적 전기적 성질에 미치는 Clay의 상승효과

단일벽 카본나노튜브 (SWCNT)/에폭시 복합체에 sodium-montmorillonite (<TEX>$Na^+$</TEX>-MMT)을 첨가하여 MMT크기와 MMT/SWCNT 비율이 복합체의 기계적 전기적 성질에 미치는 영향에 대하여 살펴보았다. 다른 크기를 갖는 3종류의 MMT를 사용하였으며, 모두 SWCNT의 분산에 효과적임을 알 수 있었다. MMT함량이 증가함에 따라 SWCNT/에폭시 복합체의 기계적인 성질은 증가하였으며, 임계함량에 도달한 후에는 감소하기 시작하였다. 그러나 표면전기저항은 MMT 함량이 증가함에 따라 감소하였으며, 임계함량에 도달한 후 증가하기 시작하였다. 최대 기계적 성질과 최소 전기특성은 임계 MMT/SWCNT 비율은 MMT 크기에 크게 의존하였으며, 이는 MMT크기가 증가함에 따라 감소하였다. Sodium-montmorillonite (<TEX>$Na^+$</TEX>-MMT) was introduced into single wall carbon nanotube (SWCNT)/epoxy composite to investigate the effect of MMT size and MMT/SWCNT ratio on the mechanical and electrical properties of composite. Three different sizes of MMTs were used and all were found to function as effective dispersion aids for SWCNTs. Mechanical properties of SWCNT/epoxy composite increased with MMT content; tending to decrease once the MMT content reached a critical level. However, the surface electrical resistance decreased with increasing MMT content and tended to increase after the critical content was reached. Critical MMT/SWCNT ratio for maximum mechanical properties and minimum electrical resistivity was strongly dependent on the MMT size. Critical MMT/SWCNT ratio was decreased with MMT size.

Role of block copolymer morphology on particle percolation of polymer nanocomposites.

In this study, the effects of nanoparticle volume fraction, block stiffness, and diblock composition on the microstructure and electrical properties of composites are investigated using molecular dynamics simulation. It is shown that selective localization of conductive nanoparticles in a continuous block of diblock copolymer can dramatically reduce the percolation threshold. In the flexible-flexible copolymer systems with a relatively low particle loading, as the ratio of two blocks varies, one sees four kinds of phase structure: signal continuous, lamellar, co-continuous, and dispersed, corresponding to the order-disorder and continuity-dispersion transitions. In consideration of particle connectivity, the best electrical performance can be achieved with a special tri-continuous microstructure. While in the semi-flexible systems, the existence of rigid blocks can destroy the lamellar structure. If particles are located in the flexible block, a moderate stiffness of the rigid block can extensively enlarge the tri-continuous region, and high conductivity can be realized over a wide range of diblock compositions. If particles are located in the rigid block, however, high conductivity only emerges in a narrow composition range. In addition, the block should be prevented from becoming overstiff because this will cause direct particle aggregation.

The Effect of Mechanical Strain on the Electrical Properties of Composites

An investigation was made of the effect of mechanical strain on the electrical properties of composites based on nitrile butadiene rubber. It was shown that general conductivity of the composite is ensured by the formation of direct contact between particles of the conductive filler, which leads to the formation of a three-dimensional conductive network within the composite. It was established that the mechanism of change in conductivity when exposed to temperature is due to thermal strain of the polymer matrix.

Elastomer composite based on EPDM reinforced with polyaniline coated curauá fibers prepared by mechanical mixing

AbstractCurauá fibers were used to reinforce elastomeric matrices with polyaniline (PAni) synthesized directly on the fiber surfaces to produce antistatic‐reinforced composites. In this work, composites of poly(ethylene‐co‐propylene‐co‐diene) with curauá fibers coated with PAni were prepared by mechanical mixing in a counter‐rotating twin rotor internal mixer. Then, mechanical and electrical properties of these composites were correlated to Raman and Fourier transformed infrared spectra (FTIR) using chemometric data analyze, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA). Raman spectra showed correlation with electrical properties of conductive composites while FTIR spectra showed good correlation with mechanical properties. EPDM reinforced with PAni coated curauá fibers presented higher tensile strength and modulus than EPDM reinforced with pristine curauá fibers, indicating that the reinforcement effect was obtained. Chemical interaction between the phases occurs with formation of hydrogen bonding between the aminic nitrogens of PAni and the carbonyl groups of lignin of the fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40056.

Synthesis of Graphene Load Nickel Nanoparticles Composites with Hydrothermal Process

This paper presents a synthetic method of graphene load nickel nanoparticles composites. Hydrothermal process is simple and convenient way, neither surfactant is needed nor by products will exist serve hydrazine hydrate as reductant. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were used to characterization the morphology of the graphene load nickel nanoparticles composites, and cyclic voltammetry (CV) was used to characterization the electrical properties of the composites. The results of XRD and FTIR show that the complexes were successfully synthesized by this method. Moreover, the good dispersibility and relatively uniform particle size of the complexes can be obviously observed from the SEM image. And the cyclic voltammetry curves exhibit good electrical properties of graphene load nickel nanoparticles composites. All the conclusions are based on the experimental results.

Numerical modelling of resistance changes in symmetric CFRP composite under the influence of structure damage

Abstract CFRP (Carbon Fibre Reinforced Polymer) composite consists of two materials characterised by different electric properties i.e., carbon fibres – the high strength component with conductive features as well as polymer fillers with insulating properties. For this reason, any structural damage will result in changes in electrical properties of the whole composite. This paper presents a mathematical FEM-based model allowing for simulation of damage in monolayer symmetric laminate structure. The dependences of electrical responses on the size and location of damage as well as the sensitivity of the method for accurate placement of electrodes supplying electric current were investigated. The effectiveness of this method for determining the approximate size and location of the damage and the usefulness of the FEM for modelling the changes in electrical properties of the composite were demonstrated.

Effect of Ni-coated short carbon fibers on the mechanical and electrical properties of epoxy composites

Ni-coated short carbon fibers (Ni-SCFs) were prepared using an electrodeposition method. Short carbon fiber (SCF) reinforced epoxy composites were prepared by changing the fiber content (0.1–0.7 wt%). To investigate the effect of Ni-coated short carbon fibers on the mechanical and electrical properties of the composites, we prepared two kinds of reinforcements: the short carbon fibers treated by 400 °C (400 °C treated SCFs) and Ni-SCFs. Fracture characteristics of the composites revealed the Ni coatings and the epoxy matrix had a better interface, so that the results of tensile and bending strength were better in epoxy/Ni-SCFs composites than those in epoxy/400 °C treated SCFs composites. The 400 °C treated SCFs decreased the electrical resistivity of the epoxy composites, compared to the pure epoxy. However the epoxy/Ni-SCFs composites had lower electrical resistivity than epoxy/400 °C treated SCFs with the same fiber content.

Effect of Carbon Black Surface Treatment on the AC Electrical Properties of PP-Based Composites

Carbon black was first activated by grafting and coupling respectively. Then the grafted carbon black, coupled carbon black, together with the unmodified carbon black was filled into polypropylene to prepare three kinds of composites respectively. The measurements of Fourier Transform Infrared Spectroscopy (FTIR) and alternating current (AC) electrical properties were performed on the composites. And the effect of CB activation on the AC electrical properties was analyzed. Seen from the result of FTIR spectra it can be found that different groups are bonded to the surface of carbon black after activation. For the corresponding conductive composites,it was found that the value of percolation threshold decreases and the electrical conductivity improves consequently after the carbon black activation. The influence of carbon black activation on the AC electrical properties of the composites and their variation with frequency was analyzed. The AC conduction mechanism was discussed and the conduction model was constructed based on the analysis.

Rheology and conductivity of carbon fibre composites with defined fibre lengths

Rheological and electrical properties of polymer composites containing conductive fillers are influenced not only by the total content of the filler but also by the shape and dimensions of filler particles markedly. However, separate treatment of these two effects is often not feasible in composites prepared by melt mixing as the filler concentration affects the flow behaviour of the melt and, thus, has an effect on the final particles geometry. In this work, composites with polymethylmethacrylate matrix and short carbon fibres with defined lengths independent on the fibre concentration were prepared and their rheology and the electrical conductivity were investigated. A pronounced influence of the fibre length on the rheological and electrical properties of the composites was confirmed. Increasing the length of the fibres the rheological quantities were affected more significantly and simultaneously the percolation threshold was shifted to lower fibre volume fractions.

Influence of Densification Method on Microstructural, Electric and Magnetoelectric Properties of the PMN-PT/NFO Composites

In this work the influence of the densification method on microstructure, electric and magnetoelectric properties of the (1-x) [0.675Pb(Mg1/3Nb2/3)O3-0.325PbTiO2] + xNiFe2O4 (PMN-PT + NFO) particulate composites, for 0.15 ≤ x ≤ 0.30 molar percent, was systematically analyzed. Conventional sintering and hot pressing as sintering methods were used. The hot pressing method affords an enhancement of the microstructural and electric properties of composites, in which samples with apparent density values close to 99% and electric resistivity larger than 107 Ω.m were obtained. On the other hand, the increase of the grain size occurring with conventional sintering affords higher ME coefficients (∼12 mV/cm.Oe). In addition, the magnetic field at which the ME is maximum increases with NFO amount, indicating a tuning of the maximum ME effect by choice of ferrite concentration.

Effect of Multiwall Carbon Nanotubes (MWCNT) on Mechanical and Electrical Properties of PP/C Composites as Alternative Materials for Bipolar Plate Fuel Cell

The properties of polypropylene can be improved by addition of multiwall carbon nanotube (MWCNT). This research focuses on material design of composite based on polymer matrix and carbon including MWCNT to improve mechanical and electrical properties of composites according to the requirement for bipolar plate material. It is found that the effect of small addition of MWCNT and Cu have been increasing electrical conductivity up to 15.62 S/cm while tensile and flexural strengths increase to 14.97 MPa and 31.78 MPa respectively.

Dissipative Processes in Pvc Systems in Weak Electric Fields

The results of experimental investigations of the electrical properties of composites based on polyvinyl chloride (PVC) and copper nanoparticles in weak electric fields are set out. It is shown that, by the action of a temperature field and a constant electric field, dissipative processes occur in the PVC system.

Electrical Resistance Properties of Cement/Carbon Fiber Composite

In this article, study results of the electrical resistance properties of cement/carbon fiber composite are presented. Using a normal mixing and compacting method, up to 0.85v.% short carbon fiber can be easily incorporated into the cement composite. And its electrical resistivity properties are measured. The resistivity of specimens decreases greatly with the volume fraction of fibers increasing. Moreover, it is found that there is a saturation point for fiber volume fraction. Beyond that, the change of resistivity with the variation of fiber volume fraction becomes much flat. Another interest finding is that the resistivity of the cement materials is a function of frequency of applied voltage. The microstructure associated with the electrical properties of composite is observed. It is possible to apply cement/carbon fiber composite as an electromagnetic shielding composite and so on.

Localization and electrical transport in onion-like carbon based composites

Electrical transport properties of onion-like carbon (OLC) based composites over a wide (20 Hz–4 THz) frequency range are reported. The dependencies of dc conductivity on temperature can be approximated by the Mott law for one-dimensional variable range hopping below 130 K and by the typical law for fluctuation induced tunneling within the range of 130–300 K. The critical frequency at low temperatures also decreases according to the Mott law for one-dimensional variable range hopping. It was demonstrated that OLC annealing temperature plays a high role on the dielectric and electrical properties of composites at low temperatures. In the terahertz frequency range, the main contribution to the complex electrical conductivity is due to the phonon contribution while the contribution from hopping conduction vanishes at these frequencies.

Electrical Properties of Composites of Polystyrene and Multi-Walled Carbon Nanotubes

The dependencies of electrical conductivity on the electrical field and temperature of high-resistivity polystyrene/carbon nanotube (CNT) composites were investigated. The electrical conductivity of the samples and their thermal activation energy were systematically dependent on the CNT doping level. Several unusual phenomena were observed which could be explained by the inhomogeneous distribution of CNTs in the polystyrene matrix. At higher levels of CNT doping, an interconnected conducting network is formed. If the amount of CNT is equal to or less than 0.6%, “islands” of CNT become separated by the layers of polystyrene, which limit charge transport. At low voltages, there is a sharper decrease in conductance as the voltage decreases.

Effect of the preparation methods on electrical properties of epoxy resin/carbon nanofiber composites

The effect of preparation methods on the electrical properties of epoxy resin/carbon nanofiber (ER/CNF) composites has been investigated. The conductivity, permittivity, and loss tangent of composite materials has been measured in the frequency range of 0.09 Hz-1 MHz in the region below and above the percolation threshold. Three main preparation methods have been used: mechanical mixing, ultrasonication in ER and a solvent. The electrical properties of composites that were prepared using ultrasonication in a solvent have been determined in a wide range of filler concentrations 0 < p < 45 wt %. It was shown that the effect of the preparation methods on the composite properties varies depending on whether the filler concentration is above or below the percolation threshold.

Polyaniline/clay as nanostructured conductive filler for electrically conductive epoxy composites. Influence of filler morphology, chemical nature of reagents, and curing conditions on composite conductivity

Electrically conductive composites based on epoxy resin, anhydride hardener and polyaniline (PANI) as conductive filler have been formulated and characterized. Standard PANI (Pani) and PANI/clay (PANICN) nanofillers were used to study the impact of filler morphology on the electrical properties of composites. Clay was used as a nanostructured template to increase the PANI aspect ratio (ratio of length to diameter or thickness). The use of PANICN reduces the electrical percolation threshold of composites from 4.5vol.% to 1.3vol.%. Moreover, the conductivity of composites containing PANICN is improved to values superior to 10−3S/cm. The effects of reagents and curing conditions were also evaluated. It was demonstrated that a classical alkaline curing accelerator, such as imidazole, exhibits chemical incompatibilities with the PANI conductive form, resulting in less conductive composites. Substituting the classical alkaline curing accelerator with a cationic accelerator, such as a Lewis acid, is a promising alternative to obtain conductive epoxy composites with a low content of PANI.