The frequency dependent dielectric relaxation behavior of conductive carbon black reinforced chlorosulfonated polyethylene (CSM) vulcanizates has been studied for different filler loadings in the frequency range of 102–106 Hz over a wide range of temperatures (30–120°C). The effects of filler loadings on the dielectric permittivity (ε′), dielectric loss tangent (tan δ), impedance, and electrical conductivity were studied. The variation of the dielectric permittivity with the filler loadings was explained on the basis of interfacial polarization of the filler in the polymer matrix. The frequency dependence of ac conductivity has been investigated using percolation theory. The effect of filler loading on the complex and real parts of impedance was clearly observed, which can be explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. The percolation threshold occurred near 30 phr of filler loading. Scanning electron microphotographs showed the agglomeration of the filler on and above these filler loadings. Additionally, the effect of temperature on dielectric loss tangent, dielectric permittivity, ac conductivity, and Nyquist plot of conductive black reinforced CSM vulcanizates has been studied. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

ABSTRACT:The effect of addition of fillers (carbon black (CB), carbon silica dual phase filler (CSDPF), and nanoclays) on the relaxation behavior of chlorobutyl vulcanizates has been studied. The primary relaxation (␣-transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (Ϫ60 to ϩ100°C) and positron annihilation life time spectroscopy (Ϫ70 to ϩ110°C). Irrespective of the filler and its loading, all the composites showed the glass transition temperature in the range of -29 to -33°C, which was explained on the basis of relaxation chain dynamics of polyisobutylene in the vicinity of fillers. The secondary relaxation (␣* or ␤ relaxation) was studied using dielectric relaxation spectra in the frequency range of 100 -10 6 Hz. Nanoclays had a profound influence on the secondary relaxation, whereas CSDPF and CB had a marginal effect. The nonlinear strain dependent dynamical parameters were also evaluated at double strain amplitudes of 0.07-5%. The nonlinearity in tan ␦ and storage modulus has been explained on the concept of filler-polymer interactions and the interaggregate attraction (filler networking). The "percolation limit" of the fillers in the composites has been studied by DC conductivity measurements.

Dynamic mechanical analysis and dielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study the relaxation behavior as a function of temperature (−90 to +100°C) and frequency (0.01–105 Hz). The effect of filler and blowing agent loadings on dynamic mechanical and dielectric relaxation characteristics has been investigated. The effect of filler and blowing agent loadings on glass transition temperature was marginal for all the composites (Tg value was in the range of −39 to −35°C), which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. Strain‐dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.07–5%. The nonlinearity in storage modulus has been explained based on the concept of filler–polymer interaction and interaggregate attraction (filler networking) of carbon black. The variation in real and complex part of impedance with frequency has been studied as a function of filler and blowing agent loading. Additionally, the effect of crosslinking on the dielectric relaxation has also been reported. POLYM. ENG. SCI., 47:984–995, 2007. © 2007 Society of Plastics Engineers

Dielectric relaxation spectra of conductive carbon black reinforced microcellular EPDM vulcanizates were used to study their relaxation behavior in the frequency range of 0.01–105 Hz over a wide range of temperature from 30 to 120°C. The effect of variation in filler loading and blowing agent loading (density) on dielectric characteristics such as impedance, dielectric constant, and conductivity has been studied. The experimental results show that the relative dielectric permittivity of the composites depends strongly on the extent of carbon black and blowing agent concentrations. The frequency dependence of AC conductivity has been investigated by using Percolation theory. The permittivity and conductivity of the microcellular composites have been analyzed based on scaling theory at increasing temperatures. The applicability of Lichtenecker‐Rother's “rule of mixture” to describe the complex permittivity of the composite has also been investigated. Irrespective of the blowing agent loading and temperature, the percolation threshold as studied by DC conductivity was found to be at 40 phr loading of the filler. Scanning electron microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

The dielectric relaxation characteristics of microcellular EPDM vulcanizates has been studied as a function of variation in filler and blowing agent loadings in the frequency range of 100-10 6 Hz. The dielectric constant e 0 increases with increasing filler loadings at all frequencies. This has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium. The effect of variation in filler and blowing agent loadings on the complex and real parts of impedance was distinctly visible. Which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by DC conductivity occurred near 40 phr of filler loading. SEM microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 28: 657-666, 2007. ª

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Cryptographic algorithms provide security against attacks during encryption of data. However, they are computationally intensive application and consume large amount of CPU time [1] and space at time of encryption. The goal of this paper is to compare the different encryption algorithm and to find space complexity of the encrypted and decrypted data by using complexities of encryption algorithm. . In this paper provide comparison between five most widely used algorithms. Based on following experimental it can be seen that TDES in general perform better than other algorithms. In this, find that how these algorithms better utilize for improving performances of algorithms in terms of space complexity. General TermsAlgorithms

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