Showing papers by "Dipak Khastgir published in 2013"
TL;DR: In this article, a light weight electromagnetic interference (EMI) shielding material from carbon nanofibers (CNFs)-based polysulfone (PSU) nanocomposites was investigated at room temperature and the measurement of EMI SE was carried out in a frequency range of 8.2.4 GHz (X-band).
Abstract: The present study aims to produce a light weight electromagnetic interference (EMI) shielding material from carbon nanofibers (CNFs)-based polysulfone (PSU) nanocomposites. EMI shielding effectiveness (EMI SE) was studied by analyzing the electromagnetic wave transmission, reflection, and absorption characteristics of nanocomposites. The electrical conductivity and EMI SE of the nanocomposite with different weight percentage of CNFs (3–10 wt%) were investigated at room temperature and the measurement of EMI SE was carried out in a frequency range of 8.2–12.4 GHz (X-band). The mechanism of EMI shielding of PSU/CNFs nanocomposite has been well explained by comparing the contribution of reflection and absorption to the total EMI SE. The state of dispersion of CNFs and PSU–CNFs interaction was studied by high resolution transmission electron microscopy and scanning electron microscopy. The thermal stability of nanocomposite studied from thermogravimetric analysis was increased after addition of CNFs to PSU matrix. Electrical conductivity of nanocomposite followed power law model of percolation theory having a percolation threshold Φc = 0.0079 vol% (0.9 wt%) and exponent t = 1.73. The EMI SE of nanocomposites with thickness of 1 mm was 19–45 decibel (dB) at 3–10 wt% CNFs loading. This high thermal stability and high EMI SE suggest the potential use of PSU/CNFs nanocomposite as effective lightweight EMI shielding material in different electronic applications.
60 citations
TL;DR: Flexible polyurethane (PU) and titania nanocomposites of different compositions are prepared by a melt-mixing technique as mentioned in this paper, and two different sequences of mixing method are adapted to prepare two different sets of composites.
Abstract: Flexible polyurethane (PU)–titania nanocomposites of different compositions are prepared by a melt-mixing technique Two different sequences of mixing method are adapted to prepare two different sets of composites All these composites show composition-dependent dielectric properties, and composites with tunable dielectric properties can be obtained through judicial adjustment of composition The morphology of these composites has been investigated by field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and scanning probe microscopy (SPM) Dielectric properties at low frequency regions are found to depend on morphology These composites show excellent piezoelectric behaviour, where the dielectric constant and conductivity of these flexible composites change appreciably with changes in applied stress The dielectric breakdown strength of these composite is also measured To understand the thermal stability of these composites, thermogravimetric analysis has been applied and it was found that a composite containing 1249 vol% titania shows higher thermal stability, beyond which, stability decreases due to the photocatalytic effect of titania
38 citations
TL;DR: In this paper, the roles of polymer matrices and filler additives in controlling the positive temperature coefficient and negative temperature coefficient (NTC) behavior of DC resistivity at high temperature for semicrystalline ethylene vinyl acetate copolymers, amorphous acrylonitrile butadiene copolymer, and their blend composites filled with different carbon fillers like Conductex carbon black, Printex carbon Black, and short carbon fiber have been investigated.
Abstract: In this study, the roles of polymer matrices and filler additives in controlling the positive temperature coefficient (PTC)/negative temperature coefficient (NTC) behavior of DC resistivity at high temperature for semicrystalline ethylene vinyl acetate copolymer, amorphous acrylonitrile butadiene copolymer, and their blend composites filled with different carbon fillers like Conductex carbon black, Printex carbon black, and short carbon fiber have been investigated. It is seen that the PTC/NTC behavior of resistivity depends on the characteristics of both polymer matrices and filler additives. The anomaly in the results are due to polymer crystallinity, shape and size of fillers, and their thermal expansion coefficient, that play major role in controlling the PTC/NTC of resistivity at high temperature for the composites. Finally, reproducibility of composite resistivity has been evaluated with their some proposed practical applications. These composites can be used as both PTC and NTC thermistors.
32 citations
TL;DR: In this article, the composites were prepared using poly(dimethylsiloxane) as base matrix and normal as well as heat-treated titania as fillers, and the dielectric and mechanical properties of the composite were measured.
Abstract: Polymer–ceramic composites were prepared using poly(dimethylsiloxane) as base matrix and normal as well as heat-treated titania as fillers. Dielectric and mechanical properties of the composites were measured and found that dielectric constant of the composites was increased dramatically with the addition of filler, whereas resistivity was decreased. Hardness and modulus were found to increase but tensile strength, % elongation at break, and tear strength were decreased with the filler loading. Neat titania contains some moisture (physisorbed and chemisorbed) as revealed from thermogravimetric analysis. Both electrical and mechanical properties of the composites were affected by filler heat treatment. Further, untreated titania contains Ti3+ and Ti4+, which on heat treatment, increases the concentration of Ti4+, as a result electrical properties were affected. Filler dispersion in the composites was studied by field emission scanning electron microscopy and high resolution transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
29 citations
TL;DR: Different nanostructured polyaniline (PAni) has been synthesized via facile template-free electrochemical synthesis approach in aqueous medium, and the best conductivity is achieved at 3:1 ratio of [H2SO4]:[PTSA].
Abstract: Different nanostructured polyaniline (PAni) has been synthesized via facile template-free electrochemical synthesis approach in aqueous medium. Instead of conventionally used aniline, aniline sulphate was used in electrochemical polymerization. The synthesis process involves simultaneous doping with combination of inorganic and organic acid, i.e., sulfuric acid (H2SO4) and p-toluenesulfonic acid (PTSA) at different ratios keeping total dopant concentration constant. Synergistic increase in conductivity is observed and the best conductivity is achieved at 3:1 ratio of [H2SO4]:[PTSA]. Different nanostructures of PAni are revealed through morphological analysis consisting of nanosphere, nanorod, and clustered particles among which finer nanorods show the best electrical conductivity. Upon controlled heat treatment followed by further cooling, resistivity increases, but after one day it decreases again and in the optimized dual doped PAni, it approaches approximately the same value of initial resistance. Lattice strain and benzenoid to quinonoid ratio increases with heat treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
22 citations
TL;DR: In this paper, the authors focused on the pressure sensitivity of polyaniline (Pani) composites prepared through in situ polymerization of aniline in solutions of insulating EVA matrix and found that both DC and AC resistivity of the composites decreases with the increase in Pani concentration.
Abstract: This study focuses on the pressure sensitivity of ethylene vinyl acetate (EVA)/polyaniline (Pani) composites prepared through in situ polymerization of aniline in solutions of insulating EVA matrix. It is found that both DC and AC resistivity of the composites decreases with the increase in Pani concentration. The investigation shows that the composites senses to applied pressure through the decrease in resistivity with the increase in applied pressure. Moreover, the pressure sensitivity is also effective when the composites are kept under constant load for a period of time. Both DC and AC resistivity are found to decrease exponentially with respect to time. Relaxation time for the composites has been calculated and found that more time is required to be relaxed for the composite with lower Pani content. However, the composite with lower Pani content exhibits relatively higher change in electrical properties when subjected to both the applied pressure and time. The results show that these composites can be used as pressure sensitive sensor. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
14 citations