Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
6 results
Search Results
Item Experimental investigation on dielectric properties of composites using Taguchi technique(Elsevier Ltd, 2020) Manohar Shankar, B.S.; Mathias, K.A.; Kulkarni, S.M.Flexible composites find applications as dielectric elastomers. These composites are used as actuators and sensors. Solid silicone rubber-conductive filler composites are promising candidates for above applications. They are fabricated using compression moulding and evaluated for their dielectric properties, using Taguchi design of experiments. The influence of factors such as filler and curing agent loading, mixing time, curing temperature on the dielectric properties are presented. Permittivity increased to 14.1 and dielectric loss increased to 1.27 for the conductive filler loading of up to 12 parts per hundred rubber, while still being in insulator regime. © 2019 Elsevier Ltd. All rights reserved.Item Influences of dielectric and conductive fillers on dielectric and mechanical properties of solid silicone rubber composites(Springer London, 2019) Manohar Shankar, B.S.; Kulkarni, S.M.Dielectric elastomers are materials being used for electromechanical transduction applications. Their electromechanical response depends on permittivity, Young’s modulus and electric breakdown strength. A factor that limits its application is high operating voltages that can be reduced through improvement in permittivity. One of the methods is by incorporating high permittivity fillers into polymer matrix to obtain dielectric–dielectric composites (DDC).These composites show high permittivity at the cost of reduced flexibility. An alternative solution is development of composites by incorporating organic or inorganic conductive fillers into polymer matrix. These composites show high permittivity with high dielectric loss and low breakdown strength. To overcome both the above limitations both dielectric and conductive fillers are incorporated into dielectric polymer matrix to obtain conductor–dielectric composites (CDC). In this study, high temperature vulcanized solid silicone rubber as matrix has been used to prepare DDC composites with barium titanate (BT) filler and CDC composites with both BT as dielectric and ketjenblack as conductive fillers, using Taguchi design of experiments. The effect of factors such as amount of fillers and curing agent, mixing time in roll mill and curing temperature on the dielectric and mechanical properties are reported. Lichtenecker model predicts the permittivity of the DDC composite more accurately. For the CDC composites permittivity increased by 390%, effective resistivity decreased by 80%, Young’s modulus increased by 368% and Shore A hardness increased by 90% as compared to those of reference matrix. Important interaction effects are observed among both the fillers that are uniformly dispersed without any aggregation. © 2019, Iran Polymer and Petrochemical Institute.Item Influence of conductive and dielectric fillers on the relaxation of solid silicone rubber composites(Institute of Physics Publishing helen.craven@iop.org, 2019) Manohar Shankar, B.S.; Hiremath, S.; Kulkarni, S.M.Flexible dielectrics possessing high permittivity and low loss are desirable for many electromechanical transduction applications. Solid silicone rubber composites are promising materials for electromechanical applications. These composites are fabricated using high-temperature vulcanization process, with various amounts of conductive, dielectric and conductor-dielectric filler and processing parameters. Dielectric and conductivity relaxations of these composites are investigated using dielectric spectroscopy in the 20 Hz-2 MHz frequency range at room temperature. Dielectric relaxations of dielectric filler composites show different behaviour compared to conductive and conductive - dielectric filler composites even with the same filler loading. All composites show increased permittivity at lower frequencies. The maximum permittivity of 46, 5.8 and 46 at 20 Hz was attained for the conductive, dielectric and conductive-dielectric composites respectively at similar filler loadings. The composites follow the AC universality law with exponents in the range of 0.82 to 1.02. The conductive filler is more reinforcing than dielectric filler as seen from the variation of Young's modulus with filler type. Uniform dispersion of fillers is observed for all the three composites. © 2019 IOP Publishing Ltd.Item Investigation on dielectric properties of PDMS based nanocomposites(Elsevier B.V., 2021) Hiremath, S.; Kevin, A.M.; Manohar, S.B.S.; Kulkarni, S.M.Polymer nanocomposites have recently been used in applications for energy storage, sensors, and actuators. The polymer materials are gaining dielectric properties such as dielectric permittivity, electrical modulus, and conductivity. In the present study, nanocomposite material is prepared by a solution cast method incorporating carbon black particles into polydimethylsiloxane. The dielectric properties of PDMS/CB nanocomposites are investigated over broad frequency using an impedance analyzer. The polymer nanocomposite's dielectric permittivity is evaluated using the various empirical models available in the literature. Compared with other methods the Wiener model is very similar to the experimental findings. For the frequency range of 100 Hz-100kHz, the frequency-dependent and independent dielectric response was observed. Nanocomposite dielectric permittivity is improved marginally with the reinforcement of carbon black particles. The nanocomposite dielectric loss moves to the higher frequency, although the losses are small. It is proved that electrical modulus can reduce the effect of polarization of electrodes. Nanocomposite AC conductivity exhibits strong frequency dependence particularly in the higher frequency region of the vicinity. This behavior obeys the power law at critical frequency, which reveals the process of relaxing conductivity. The PDMS/CB nanocomposites power-law exponent is within a range of 0.48–0.57. Eventually, empirical and experimental inspections are the basis framework for designing electronic devices based on polymers. © 2020 Elsevier B.V.Item Experimental studies on mechanical and dielectric behavior of Glycerol filled Silicone rubber composites(IOP Publishing Ltd, 2021) Mathias, K.A.; Hiremath, H.; Kulkarni, S.M.In this study, Silicone rubber composites are prepared with Glycerol filler in three different volume fractions. The samples developed are subjected to mechanical and dielectric testing. The tensile strength increases first and later decreases with Glycerol loading whereas compression strength decreases with Glycerol loading. Modulus of elasticity in tension and compression both decreases with the increase of Glycerol loading. Dielectric permittivity, dissipation factor and conductivity are increases with the increase of Glycerol loading. The Silicone Rubber (SR) composite with 15% volume of Glycerol filler shown a maximum reduction in modulus of elasticity of 29% (in tension) and 16.8% (in compression), and maximum improvement in the dielectric permittivity of 112% compared to neat silicone rubber. The reduction in modulus of elasticity with an increase in dielectric permittivity with an increase in Glycerol loading suggests that this material is a potential candidate for materials to be used in soft dielectric sensors and actuator applications. © 2021 IOP Publishing LtdItem Study on low-frequency dielectric behavior of the carbon black/polymer nanocomposite(Springer, 2021) Hiremath, H.; Mathias, K.A.; Sondar, P.R.; Shrishail, M.H.; Kulkarni, S.M.Recently, polymer-based dielectric materials have become one of the key materials to play an essential role in clean energy production, energy transformation, and energy storage applications. The end usage is the energy storage capability because it is a trade-off between dielectric permittivity, dielectric loss, and dissipation factor. Hence, it is of prime importance to study the dielectric properties of polymer materials by adding filler material at a low-frequency range. In the present study, polydimethylsiloxane/carbon black nanocomposites are prepared using the solution cast method. The dielectric properties, such as dielectric constant, dielectric loss, and dissipation factors due to the concentration of filler particles and low-frequency effect on the nanocomposites, are examined. Also, different empirical models are used to estimate the dielectric permittivity of polymer nanocomposites. The low-frequency range of 100 Hz to 1 MHz and the effect of varying volume fractions of carbon black show a significant change in the dielectric properties. It is found that the nanocomposites have a higher dielectric permittivity than the base polymer material. It is also observed that an increase in filler concentration increases the dielectric permittivity, which is confirmed with an empirical model. © 2021, The Author(s).