Abstract:The purpose of this study is to identify the relationship between the electrical and structural characteristics of multiwalled carbon nanotubes dispersed into the polymer matrix of a resin. In a first step, the composites were characterized by small-angle neutron scattering, which provide information about the bulk dispersion of nanotubes in the matrix and form three-dimensional networks with a surface fractal behavior. In the second step, a dielectric and electrical study was carried out in the frequency rang… Show more
“…The real and the imaginary parts of the complex permittivity were calculated from the measured admittance, of the equivalent circuit leading to and , where B is the susceptance, G is the conductance, is the frequency, is the vacuum dielectric constant, and h and d are the thickness and the diameter of the sample, respectively. The measurements were performed, in the frequency range 40 Hz to 1 MHz, under isothermal conditions, for temperatures ranging between 200 and 400 K. Estimating relative errors on both real and imaginary parts of the complex permittivity are Δε′/ε′=Δε″/ε″≤5% .…”
“…The real and the imaginary parts of the complex permittivity were calculated from the measured admittance, of the equivalent circuit leading to and , where B is the susceptance, G is the conductance, is the frequency, is the vacuum dielectric constant, and h and d are the thickness and the diameter of the sample, respectively. The measurements were performed, in the frequency range 40 Hz to 1 MHz, under isothermal conditions, for temperatures ranging between 200 and 400 K. Estimating relative errors on both real and imaginary parts of the complex permittivity are Δε′/ε′=Δε″/ε″≤5% .…”
“…However, finer particles tend to agglomerate and this can cause disadvantageous effects on mechanical properties. Due to their unique properties 10 , MWCNTs have emerged as the most promising nanofiller candidate for polymer composites 11–15 as of their discovery 16 . MWCNTs with rolled graphitic layers with remarkable mechanical 17–19 , thermal 20,21 and electrical 22–24 properties can be applied as reinforcement of fiber/matrix composites to achieve improved properties.…”
In the present publication, multiwalled carbon nanotubes (MWCNT) coated with SiO2–MgO nanoparticles were successfully fabricated via sol–gel method to facilitate their incorporation into polymer matrices. Magnesium acetate tetrahydrate and tetraethyl orthosilicate were used as precursors. The coated MWCNTs were characterized by transmission electron microscopy (TEM), X–ray diffraction (XRD) and Raman spectroscopy methods. These investigation techniques verified the presence of the inorganic nanoparticles on the surface of MWCNTs. Surface coated MWCNTs were incorporated into polyamide (PA), polyethylene (PE) and polypropylene (PP) matrices via melt blending. Tensile test and differential scanning calorimetry (DSC) investigations were performed on SiO2–MgO/MWCNT polymer composites to study the reinforcement effect on the mechanical and thermal properties of the products. The obtained results indicate that depending on the type of polymer, the nanoparticles differently influenced the Young’s modulus of polymers. Generally, the results demonstrated that polymers treated with SiO2-MgO/MWCNT nanoparticles have higher modulus than neat polymers. DSC results showed that nanoparticles do not change the melting and crystallization behavior of PP significantly. According to the obtained results, coated MWCNTs are promising fillers to enhance mechanical properties of polymers.
“…Typical experimental values are ≤2 for three-dimensional systems, but some works determine slightly higher values. 20,21 Of course, the estimation of the percolation threshold depends on the critical exponent (see Figure 8), but since the differences are below 2%, the accuracy of this procedure is not influenced significantly. Figure 8.Percolation threshold for various axis lengths L ‖ and critical exponents t .…”
Carbon nanotube reinforced polymers belong to a class of composite materials, which have been largely investigated due to their specific electrical, thermal and mechanical properties. In the case of electrical conductivity of carbon nanotube reinforced polymers, a critical amount of filler material ensures a sharp increase of conductivity. The material forms a percolation pathway and instantly turns the composite into a conductor. Mesoscopic simulations of these materials were carried out to predict electrical conductivity of carbon nanotube reinforced polymers and their critical amounts. This research work deals with percolation thresholds, converging representative volume elements and the effect of the discontinuous behaviour of conductivity considering tunnelling effects found in atomistic approaches on mesoscopic simulation models.
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