Dielectric behavior of Silica/Poly(dimethylsiloxane) nanocomposites. nano size effects (original) (raw)
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Dielectric silicone elastomers with mixed ceramic nanoparticles
Materials Research Bulletin, 2015
A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by Transmission Electron Microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular masses, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.
Polymer Nanocomposite Dielectrics – The Role of the
Dielectrics and …, 2005
The incorporation of silica nanoparticles into polyethylene increased the breakdown strength and voltage endurance significantly compared to the incorporation of micron scale fillers. In addition, dielectric spectroscopy showed a decrease in dielectric permittivity for the nanocomposite over the base polymer, and changes in the space charge distribution and dynamics have been documented. The most significant difference between micron scale and nanoscale fillers is the tremendous increase in interfacial area in nanocomposites. Because the interfacial region (interaction zone) is likely to be pivotal in controlling properties, the bonding between the silica and polyethylene was characterized using Fourier Transformed Infra-red (FTIR) spectroscopy, Electron Paramagnetic Resonance (EPR), and X-ray Photoelectron Spectroscopy (XPS) The picture which is emerging suggests that the enhanced interfacial zone, in addition to particle-polymer bonding, plays a very important role in determining the dielectric behavior of nanocomposites.
Dielectric properties of polymer nanoparticle composites
Polymer, 2007
Well-dispersed high dielectric permittivity titanium dioxide (TiO 2 ) nanoparticles were synthesized utilizing a block copolymer as a template. The nanoparticles were confined within microphase separated domains of sulfonated styrene-b-(ethylene-ran-butylene)-b-styrene (S-SEBS) block copolymers. A crosslinker (vinyltrimethoxysilane) was incorporated into the block copolymer matrices in order to decrease the dielectric loss from the free sulfonic acid groups. Dynamic mechanical analysis experiments confirmed that nanoparticles and crosslinker were confined within the crosslinked sulfonated styrene blocks and had no effect on the chain relaxation behavior of [ethylene-ran-butylene] blocks. Dielectric experiments showed that higher permittivity composites can thus be obtained with a significant decrease in loss tan d (<0.01) when crosslinked with vinyltrimethoxysilane.
The Promise of Dielectric Nanocomposites
Conference Record of the 2006 IEEE International Symposium on Electrical Insulation, 2006
Several research groups worldwide have now been able to document some significant improvements that can be made in the electrical, and other, properties of polymer composites through the incorporation of nanoparticulates. Although it is now becoming clear that the mechanisms responsible for these changes are by no means universal, some of the benefits are substantial and rely on the large interface areas which are inherent in the introduction of materials of nanometric dimensions. By examining a variety of nanomaterials, this contribution seeks to review the property changes that can be brought about and examines the possibilities for commercial applications. This involves not only the electrical properties, but the implications for the attendant mechanical characteristics and the polymer processing necessary for utilization of this emerging breed of dielectric material. In this context, the functionalization of the particulate surfaces to provide preferential coupling to the host polymer will be explored since, by this means, a degree of preferred assembly can be accommodated. Through experimental examples, the use of this technique to tailor the properties of nanodielectrics is illustrated.
ABSTRACT: Hybrid silica spheres (HS) of size 270−350 nm with vinyl and aminopropyl surface groups were incorporated in polystyrene (PS), and its effect on dielectric properties, coefficient of thermal expansion (CTE), and strength of PS−HS composite was studied. Incorporation of HS in PS followed a decrease in the dielectric constant from 3.2 for PS to 2.6 for composite with 7.5 vol % HS. The decrease in the dielectric constant was attributed to (i) increased interfacial porosity, (ii) formation of anhydrous HS having low dielectric constant, during hot processing of the composites, and (iii) dispersion and preservation of the anhydrous HS in the hydrophobic matrix. The dielectric constant of the composites with HS content up to 7.5 vol % does not vary much with temperature in the range from −20 to 65 °C. These composites also exhibited reduced CTE and improved flexural strength/stiffness due to good interfacial bonding through HS vinyl groups and dispersion of the filler in the matrix. The dielectric loss increased with HS content, and the loss measured for 7.5 vol % PS−HS composite was 6 × 10−3, as compared to 10−4 for PS. At HS loading above 7.5 vol %, the tendency of HS to agglomerate and form percolated structure lead to an increase in the dielectric constant and decrease in the mechanical properties of the composites.
Tensile, Thermal, Dielectric and Morphological Properties of Polyoxymethylene/Silica Nanocomposites
Journal of nanoscience and nanotechnology, 2018
This paper presents the tensile, thermal, dielectric and morphological properties of composites based on polyoxymethylene (POM) and nanosilica (NS) prepared by melt mixing method at 190 °C. Based on the torque readings, the processing of POM/NS composites were found to be easier in comparison to only POM. The FT-IR spectra analysis of the POM/NS nanocomposites showed the presence of peak at approximately 910 cm-1, attributed to the Si-O and C-O groups in NS and POM on the POM/NS nanocomposite. The absorption at these peaks increased on gradually increasing the content of NS. Tensile property testing (tensile strength, elongation at break, and Young's modulus) indicated that the tensile strength of POM/NS nanocomposites increases as the NS content increases from 0.5 wt.% to 1.5 wt.%, and sharply dropped when the NS content was more than 2 wt.%. A similar trend was observed for Young's modulus and elongation at break of the nanocomposites. The DSC analysis of the nanocomposite...
High Performance Polymers, 2016
Three new, cheap, and easily obtained complexes of triethanolamine with Cu(II), Ni(II), and Co(II) were incorporated in a high-molecular-weight polydimethylsiloxane-α,ω-diol (number-average molecular weight = 440,000 g mol−1) together with silica nanoparticles. While silica has a well-known mechanical reinforcing role, adding the metal complexes with high dielectric permittivity aims to increase values for this characteristic of the prepared silicone composites in order to be useful for electromechanical applications. A simple procedure was employed for the incorporation of fillers by mechanical mixing in bulk without a solvent. The composites were processed as films and stabilized by curing initiated with 2,4-dichlorobenzoyl peroxide at high temperature (180°C) and pressure. The cross-linking yield was estimated on the basis of swelling in chloroform, while the cross-linking density was calculated from differential scanning calorimetry traces. The filler’s effect on mechanical and ...
European Polymer Journal, 2017
Polyoxymethylene/Polyurethane/Layered Silicates (POM/PU/LS) ternary hybrid nanocomposites were prepared by two methods: (a) direct melt compounding (DM) and (b) melt compounding using a latex-mediated masterbatch (MB) technique. The morphology of the produced specimens and the quality of the dispersion of LS (synthetic sodium fluorohectorite) were examined via Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Broadband dielectric spectroscopy (BDS) was employed in order to study the dielectric response of the two systems in a wide frequency and temperature range. Rich dielectric spectra are recorded, since dielectric relaxation mechanisms originate from POM matrix, PU latex as well as from interfacial phenomena between LS and the polymer matrix. Six different mechanisms were observed in the spectra of the examined
Journal of Applied Polymer Science, 2012
Effects of silica and silica/titania nanoparticles on glass transition and segmental dynamics of poly(dimethylsiloxane) (PDMS) were studied for composites of a core-shell type using differential scanning calorimetry, thermally stimulated depolarization current, and dielectric relaxation spectroscopy techniques. Strong interactions between the filler and the polymer suppress crystallinity (T c , X c) and affect significantly the evolution of the glass transition in the nanocomposites. The segmental relaxation associated with the glass transition consists of three contributions, arising, in the order of decreasing mobility, from the bulk (unaffected) amorphous polymer fraction (a relaxation), from polymer chains restricted between condensed crystal regions (a c relaxation), and from the semibound polymers in an interfacial layer with strongly reduced mobility due to interactions with surface hydroxyls of silica and silica/ titania nanoparticles (a 0 relaxation). The evolution of surface affected CH 3 groups, as well as the degree of interaction of PDMS molecules with surface hydroxyl groups as a function of treatment temperature, was assessed by Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis. The effectiveness of silica/PDMS and silica/titania/PDMS nanocomposites as hydrophobic coatings was investigated by static contact angle measurements. It was shown that the presence of titania nanoparticles and adsorbed PDMS promotes the hydrophobic properties of the PDMS coating after treatment in the 80-650 C range. V