Dielectric relaxation behavior of multi-walled carbon nanotube (MWCNT)-reinforced silicone elastomer nanocomposites has been studied as a function of filler loading in a wide frequency range (10−1–106 Hz). The effect of MWCNT loading on the real and imaginary parts of impedance is distinctly visible. The significant change in the impedance parameters on filler loading is explained on the basis of interfacial polarization in a heterogeneous medium and relaxation dynamics of polymer chains. The electrical modulus formalism has been used to investigate the conductivity and relaxation phenomena of the system. The frequency dependence of ac conductivity is explained using percolation theory. The existence of percolation phenomenon in the composites is discussed on the basis of electrical conductivity and morphology of the composites. The percolation threshold (as studied by electrical conductivity) occurs in the range of 4 phr of MWCNT loading. The scanning electron photomicrographs show agglomeration of the MWCNT above 4 phr concentration and formation of a continuous network structure.
MacFarlandEWWeinbergWH. Combinatorial approaches to materials design. Tibtech1999; 17:107–115.
2.
GilorminiPBrechetY. Syntheses: Mechanical properties of heterogeneous media: Which material for which model? which model for which material?Modelling and Simulation in Materials Science and Engineering1999; 7:805–816.
3.
KrausG. Reinforcement in Elastomers, New York, NY: Wiley-Interscience, 1965.
4.
GojnyFHWichmannMHGFiedlerBKinlochIABauhoferWWindleAH. Evaluation and identification of electrical and thermal conduction mechanism in carbon nanotube/epoxy composites. Polymer2006; 47:2036–2045.
5.
E1-TartawyFKamadaKOhnabeH. In situ network structure, electrical and thermal properties of conductive epoxy resin carbon black composites for electrical heater applications. Mater Lett2002; 56:112–126.
6.
ZhengWWongSCSueHJ. Transport behavior of PMMA/expanded graphite nanocomposites. Polymer2002; 73:6767–6773.
7.
ChungDDL. Electrical applications of carbon materials. J Mater Sci2004; 39:2645–2661.
8.
LijimaS. Helical microtubules of graphite carbon. Nature1991; 354: 56–58.
ShanmugharajAMBaeJHLeeKYNobWHLeeSHRyuSH. Physical and chemical characteristics of multiwalled carbon nanotubes functionalized with aminosilane and its influence on the properties of natural rubber composites. Comp Sci Tech2007; 67:1813–1822.
SandlerJShafferMSPPrasseTBauhoferWSchulteKWindleAH. Development of a dispersion process for carbon nanotubes in an epoxy matrix and the resulting electrical properties. Polymer1999; 40:5967–5971.
14.
JeroenWGWLiesbethCVAndrewGRRichardES. Electronic structure of atomically resolved carbon nanotubes. Nature1998; 391:59–62.
15.
SinnottSB. Chemical functionalization of carbon nanotubes. J Nanoscience and Nanotechnol2002; 2:113–123.
16.
ZhouWWoYWeiFLuoGQianW. Elastic deformation of multiwalled Carbon nanotubes in electrospun MWCNTs-PEO and MWCNTs-PVA nanofibers. Polymer2000;46:12689–12695.
17.
KimHSMyungSJJungRJinHJ. Microspherical poly(methyl Methacrylate) multiwalled carbon nanotube composites prepared via in situ Dispersion polymerization. J Nanosci Nanotechnol2007; 7:4045–4048.
18.
KoleSBhattacharyaAKBhowmickAK. Morphology and mechanical properties of silicone-EPDM blends. Plast. Rubber Compos Process Appl.1993;19:117–125.
19.
KimESKimHSJungSHYoonJS. Adhesion properties and thermal degradation of silicone rubber. J Appl Polym Sci2007; 103:2782–2787.
20.
KimJKKimIH. Charecteristics of surface wettability and hydrophobicity and recovery ability of EPDM rubbers and silicone rubber for polymer insulators. J Appl Polym Sci2001; 79: 2251–2257.
21.
ZhangNXieJVaradanVK. Functionallization of carbon nanotubes by Potassium permanganate assisted with phase transfer catalyst. Smart Mater Struct2002;11:962–965.
22.
Mc-CrumNGReadBEWilliamsG. Anelastic and Dielectric Effects in Polymeric Solids, Dover edition, New York, NY: Dover Inc, 1991.
23.
JawadSAAlnajjarA. Frequency and temperature dependence of ac electrical properties of graphitizied carbon-black filled rubbers. Polym. Inter1997; 44: 208–212.
24.
WangYJPanYZhangXWTaK. Impedance spectra of carbon black filled high-density polyethylene composites. J App Poly Sci. 2005; 98:1344–1350.
25.
KestelmanVPinchukLGoldadeV. Electrets in engineering: Fundamentals and applications. Boston, USA. Kluwer Academic Publishers, 2000.
26.
PinchukLSJurkowskiBJurkowoskaBKravtovAGGoldadeVA. An On some variations in rubber charge state during processing. Eur Polym Journal2001; 37:2239–2243.
27.
HuberGVilgisTA. On the Mechanism of Hydrodynamic Reinforcement in Elastic Composites Macromolecules. 2002; 35:9204–9210.
28.
KluppelMHeinrichG. Fractal structures in carbon black reinforced rubbers. Rubber Chem Technol. 1995; 68:623–651.
29.
KniteMTeterisVKiplokaAKlemenoksI. Reversible Tenso-Resistance and Piezo-Resistance Effects in Conductive Polymer-Carbon Nanocomposites. Adv Eng Mater.2004; 6:742–746.
30.
McLachlanDSChitemeCParkCWiseKELowtherSELilleheiPTSiochiEJHarrisonJS. AC and DC percolative conductivity of single wall carbon nanotube polymer composites. J Poly Sci B2005; 43:3273–3287.
31.
WiseKEParkCSiochiEJHarrisonJS. Stable dispersion of single wall carbon nanotubes in polymide: the roll of noncovalent interactions. Chem Phys Lett2004; 391: 207–211.
32.
BottgerHBryskinVV. Hopping conduction in solids. Berlin, Germany : Akademie-Verlag, 1985, pp. 169–213.
33.
GhoshPChakrabartiA. Conducting carbon black filled EPDM vulcanizates: Assessment of dependence of physical and mechanical properties and conducting character on variation of filler loading. European Polymer Journal2000; 36:1043–1054.
34.
JonscherAK. The ‘universal’ dielectric response. Nature1977; 267: 673–679.
35.
YingXYuezhenBChiangCKMasaruM. Dielectric effects on positive temperature coefficient composites of polyethylene and short carbon fibers. Carbon2007; 45:1302–1309.
36.
BrandrupPImmergutEH. Polymer Handbook, 3rd ed. New York, NY: Wiley Interscience, 1989.
