J Polym Res (2012) 19:16 DOI 10.1007/s10965-012-0016-1

ORIGINAL PAPER

Influence of matrices chemical nature on the dynamic mechanical and dielectric properties of rubber composites comprising conductive carbon black
Omar A. Al-Hartomy & Ahmed A. Al-Ghamdi & Falleh Al-Solamy & Nikolay Dishovsky & Mihail Mihaylov & Milcho Ivanov & Farid El-Tantawy
Received: 14 February 2012 / Accepted: 22 October 2012 # Springer Science+Business Media Dordrecht 2012

Abstract The study presents the effect that elastomeric matrices different in their chemical nature (a non-polar and crystallizing natural rubber and a polar and non-crystallizing acrylonitrile-butadiene rubber) have upon the dynamic mechanical and dielectric properties of the composites comprising different amounts of conductive carbon black. Dynamic mechanical thermal analysis (DMTA) and Dielectric thermal analysis (DETA) are the techniques used for studying the structure-properties relationships of the composites. The experimental results show that the matrices studied and their specific properties have a great impact
O. A. Al-Hartomy : A. A. Al-Ghamdi Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia O. A. Al-Hartomy Department of Physics, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia F. Al-Solamy Department of Mathematics, Faculty of Science, University of Tabuk, Tabuk 71491, Saudi Arabia F. Al-Solamy Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia N. Dishovsky (*) : M. Mihaylov : M. Ivanov Department of Polymer Engineering, University of Chemical Technology and Metallurgy, 8 Kl. Ohridski Blvd., 1756, Sofia, Bulgaria e-mail: dishov@uctm.edu F. El-Tantawy Department of Physics, Faculty of Science, Suez Canal University, Ismailia, Egypt

upon both the dynamic mechanical and dielectric parameters of the composites based on them. The chemical nature, structure and specific characteristics of the matrix affect the storage modulus, glass transition temperature, elasticity behavior, high-elasticity, energy dispersion, dielectric permittivity and DETA tan δ of the composites investigated. The matrix effect dominates at lower filler amounts and determines the properties of the composites. Keywords Rubber composites . Carbon black . DMTA . DETA . Viscoelastic Properties

Introduction Dynamic mechanical thermal analysis (DMTA) is a technique where a small deformation is applied to the sample investigated in a cyclic manner. The force applied to the sample oscillates allowing to obtain information about the changes in stiffness and damping, which are reported as modulus and tan δ. Because the applied force is sinusoidal one can express the modulus as an in-phase component (so called storage modulus) and an out of phase component (the loss modulus). The storage modulus (E’) is the measure of the sample elastic behavior, the loss modulus (E”) is the measure of the viscous response of materials. The ratio of the loss modulus to the storage modulus (E”/E’) is tan δ and it is a measure of the energy dissipation in the material. Tan δ is also an indicator of the viscoelasticity of the sample [1]. Viscoelasticity is the ability of a composite to exhibit both elastic and viscous behavior. Dielectric thermal analysis (DETA) is a technique for studying molecular dipolar relaxation as a function of temperature and frequency. By studying the relaxation spectra the intermolecular cooperative motion and hindered dipolar rotation can be deduced. Due to the presence of an electric

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field, the composite undergo ionic, interfacial and dipole polarization and this polarization mechanism largely depends on time scales. As a result this technique reveals the dynamic of the macromolecular chains of the rubber matrix [2]. With the development of electronic industry, some special dielectric materials with high and/or low dielectric permittivity are attracting a remarkable attention in academic and industrial fields. The dielectric properties of the insulative materials could be adjusted by dispersing different kinds of fillers into polymer matrices to form the polymer/ filler composites. With changing the concentration of fillers, the dielectric permittivity could be changed. When filler with low dielectric permittivity is added into the polymers, the composites with low dielectric permittivity could be acquired. While the inorganic or organic fillers with high dielectric permittivity are added into the polymers, composites with high dielectric permittivity should be acquired [3]. The electroconductive rubber compounds find wide application in the production of versatile static electricity insulators. Usually the electrical conductivity (percolation threshold) of the vulcanizates comprising conventional (low structure) carbon black is achieved at a high filling degree (70–80 phr). However, the higher filling degree causes considerable changes in the elastic properties of the vulcanizates. In other cases, filling the rubber compounds with small quantities of high structure electrically conductive carbon black affords the percolation threshold at lower filler amounts with no significant changes upon the mechanical properties of the vulcanizates based on the said compounds. It is obvious that DMTA and DETA are important and powerful tools for studying the structure-properties relationships in polymer composites and nanocomposites [4]. They elucidate the mechanical behavior and the molecular structure of rubber based materials. The dynamics of polymer chain relaxation and molecular mobility of polymer main chains and side chains is one of the factors that determine the viscoelastic properties of the polymeric macromolecules [5, 6]. There is a number of papers reporting on DMTA and DETA studies presenting the effect that the filler’s structure
Table 1 Typical properties of the carbon black used Iodine adsorptiona mg/g 300 a b

and chemical nature have on the composites characteristics mentioned above (tan δ peak height, the shift in the peak position, the values of storage modulus, the value of loss modulus, polymer chain dynamics) [7–20], which describe the composites macroproperties (elastic behavior, viscous response, viscoelasticity, energy absorption). However, few are the articles reporting on DMTA and DETA investigations on the effect of the elastomeric matrix. [21–25]. The goal of this paper is to present how under the same conditions the dynamic, mechanical and dielectric properties of composites filled with conductive carbon black depend on the chemical nature and structural characteristics of two completely different elastomeric matrices (a polar noncrystallizing and a non-polar crystallizing one).

Experimental Materials Acrylonitrile-butadiene rubber (NBR) Acrylonitrile-butadiene rubber, containing 26 % ACN (Krynac 2645F, produced by Lanxess) was used in our investigations. Natural rubber (NR) Natural rubber—SVR 10 was purchased from North Special Rubber Corporation of Hengshui, Hebei Province, China. Characterization of the carbon black used Furnace carbon black Printex L6 (produced by Evonik) was chosen for the experiments. Some of the most often used carbon black characteristics are surface area, dibutylphtalate (DBP) adsorption, iodine adsorption number, etc. The main characteristics of the filler are summarized in Table 1 [26].

CTAB-surface areab m2/g 136

BET surface areac m2/g 150

DBP absorptiond ml/100 g 119

CDBP absorptione ml/100 g 103

Primary particle size, nm 10–80

The iodine number (iodine adsorption) reflects a “not true” surface area, because it is affected by porosity, surface impurities and surface oxidation

The cetyltrimethyl ammonium bromide (CTAB) surface area analyzes the so-called external surface area which corresponds to the accessible surface area for an elastomer c d e

BET (Brunauer, Emmett, Teller) nitrogen adsorption surface area provides the “total” surface area including porosity DBP absorption–dibutylphtalate absorption CDBP absorption–crushed DBP

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Preparation and vulcanization of rubber compounds The rubber compounds were prepared on an open two-roll laboratory mill (L/D 320×360 and friction 1.27). The speed of the slow roll was 25 rpm. The formulations of the compounds prepared and studied are shown in Tables 2 and 3. The experiments were repeated for verifying the statistical significance. The ready compounds in the form of sheets stayed 24 h prior to their vulcanization. The optimal curing time was determined by the vulcanization isotherms taken on an oscillating disc vulcameter MDR 2000 (Alpha Technologies) at 150 °C for NR based composites and at 160 °C for NBR based composites, according to ISO 3417:2002.

the temperature range from −80 °C to 80 °C using a heating rate of 3 °C/min under single cantilever bending mode. The dimensions of the investigated samples were as follows: width 10 mm, length 25 mm and the thickness measured using a micrometer varied between 1 and 2 mm. Dielectric thermal analysis Dielectric properties (Permittivity (ε’) and dielectric loss angle tangent (DETA tan δ)) were investigated using a Dielectric Thermal Analyzer (Rheometric Scientific) at 4 different frequencies (1 kHz, 10 kHz, 100 kHz and 1 MHz) and temperature 30 °C and 100 °C on a sample having a diameter approximately 32 mm and 1 mm thickness.

Measurements Dynamic mechanical thermal analysis (DMTA) Dynamic properties (Storage modulus (E’) and mechanical loss angle tangent (tan δ)) of the studied vulcanizates were investigated using a Dynamic Mechanical Thermal Analyzer Mk III system (Rheometric Scientific). The data were obtained at 5 Hz frequency and strain amplitude 64 μm in Results and discussion In order to explain adequately the properties of elastomercarbon composites one should take into account the bellow specifics of their matrices. Natural rubber is a linear polymer of an unsaturated hydrocarbon called isoprene (2-methyl butadiene).

nCH2

C CH3

CH

CH2

CH2

C CH3

CH

CH2 n

Isoprene [2-methyl butadiene]

Natural rubber [Polyisoprene]

Crude rubber is a tough and elastic solid. With rising temperature it becomes soft and sticky. The most important property of natural rubber is its elasticity. When stretched, it
Table 2 Composition of the NBR based rubber compounds NBR 0 Acrylonitrile-butadiene rubber (NBR-26 ACN) ZnO Stearic acid Carbon black-Printex L6 TBBSa Sulfur a expands and attains its original state, when released. That is due to the coil-like structure of its molecules which straighten out when stretched and when released, they coil up again.

NBR 10 100 4 2 10 0.8 2.25

NBR 20 100 4 2 20 0.8 2.25

NBR 30 100 4 2 30 0.8 2.25

NBR 40 100 4 2 40 0.8 2.25

NBR 50 100 4 2 50 0.8 2.25

100 4 2 – 0.8 2.25

TBBS N-tert-Butyl-2-benzothiazolesulfenamide

Page 4 of 8 Table 3 Composition of the NR based rubber compounds Natural Rubber SMR 10 ZnO Stearic Acid Carbon black Printex L6 TBBSa Sulfur

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NR 0 100 5 2 0 0.8 2.25

NR 10 100 5 2 10 0.8 2.25

NR 20 100 5 2 20 0.8 2.25

NR 30 100 5 2 30 0.8 2.25

NR 40 100 5 2 40 0.8 2.25

NR 50 100 5 2 50 0.8 2.25

a

TBBS N-tert-butyl-2benzothiazolesulfenamide

Therefore applied stress can easily deform rubber. Noteworthy is that when the stress is removed, the rubber retains its original shape. Raw natural rubber is elastic over a narrow temperature range from 10 to 60 °C. That is why articles made of raw natural rubber fail to perform in hot weather. Pure rubber is a transparent, amorphous solid which upon stretching or prolonged staying crystallizes. It is a non-polar elastomer and a dielectric possessing very high values of volume resistivity [27, 28]. Acrylonitrile-butadiene rubber (NBR) is a synthetic rubber produced by copolymerization of acrylonitrile (ACN) with butadiene, mainly in a trans-1.4 structure.

Dynamic mechanical thermal analysis of the composites Figure 1 presents the temperature dependences of the storage modulus (E’) for NBR (Fig. 1a) and NR (Fig. 1b) vulcanizates comprising various amounts of conductive carbon black. As seen from Fig. 1 NBR vulcanizates are in the glass state in the −60 °C÷−30 °C range and NR vulcanizates are in the glass state in the −80 °C÷−40 °C region. In the above temperature intervals the storage modulus (E’) values for NR based vulcanizates are slightly higher than those for NBR ones. That is due to differences in the chemical nature of the said elastomers. As already mentioned, storage modulus (E’) is a measure of the elastic behaviour of the material studied. Obviously, NR and its vulcanizates are more elastic than NBR and its vulcanizates. That difference in the properties of the two rubbers is well known [28–30]. During the transition from the glass into the high-elastic state occurring at about −30 °C for NBR composites and at about −40 °C for NR composites, storage modulus start to decrease with the increasing temperature. Тhis sharp decrease over 2–3 decades corresponds to the primary relaxation process associated with the glass-high elastic transition of the material [13]. As one can see later, this modulus drop corresponds also to an energy dissipation phenomenon observed during the concomitant relaxation process, where tan δ passes through a maximum. Then the storage modulus reaches a plateau around 1 MPa, corresponding to the rubber state. Generally the storage modulus values for NR in the said plateau are higher because its elasticity is better than the one of the NBR.

CH2

CH

CH

CH2 m

CH2

CH CN n

The acrylonitrile (ACN) content is one of the two primary criteria for defining every NBR. The ACN level, by reason of polarity, determines several basic properties, such as oil and solvent resistance, low temperature flexibility, glass transition temperature (Tg) and abrasion resistance. Generally acrylonitrile-butadiene rubber can be used down to about −30 °C but special grades of NBR can work at lower temperatures too. Acrylonitrile-butadiene rubber belongs to the class of unsaturated copolymers of acrylonitrile and butadiene. The rubber is generally resistant to fuel and oils. It has inferior strength and flexibility, compared to natural rubber. It is a strongly polar (due to the nitrile group presence in its structure), non-crystallizing elastomer and a semiconductor [27, 28].
Fig. 1 Storage modulus (E’) dependency on the temperature at various filler content for (a) NBR and (b) NR based composites

J Polym Res (2012) 19:16 Fig. 2 Dependency of mechanical loss angle tangent (tan δ) on the temperature at various filler content for (a) NBR and (b) NR based composites

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In the −20 °C ÷ −80 °C range wherein the samples studied are in the high-elastic state, storage modulus (E’) values for NR (Fig. 1b) vulcanizates increase with the increasing amount of conductive carbon black. That is on account of the restricted, decreased mobility of the macromolecules following their immobilization onto the fillers surface and first of all because of the immobilization onto carbon black particles. In correspondence with [31] the decrease in mobility leads to an increase in E’ which allows to use this effect as a measure for fillers reinforcing activity. In the the −20 °C÷ 80 °C range storage modulus (E’) values for NBR (Fig. 1a) composites are also higher at higher filler amounts but the tendency is not as that pronounced. As a whole storage modulus (E’) values for NBR, although remaining lower in most cases, are quite close to those of NR which is probably due to NR crystallizability. Hence, the effects of the filler and its reinforcement are lesser than those in the case of NBR composites. Consequently the storage modulus (E’) values for the two types of elastomer matrices are equalized in a way. Mechanical loss angle tangent (tan δ) being the ratio between the dynamic loss modulus (E”) and dynamic storage modulus (E’) (tan δ0E”/E’) illustrates the macromolecules mobility as well as the phase transition in the polymers [30]. Figure 2 presents the temperature dependence of mechanical loss angle tangent (tan δ) for NBR (Fig. 2a) and NR (Fig. 2b) vulcanizates comprising various amounts of conductive carbon black.
Fig. 3 Dielectric permittivity (ε′) dependence on the filler amount and frequency for the composites on the basis of (a) NBR and (b) NR at 30 °C

As seen from Fig. 2 there are not considerable differences in the values of mechanical loss angle tangent (tan δ) as a function of the filler amount in the 0 °C÷80 °C range. However, in the said temperature range the values of mechanical loss angle tangent (tan δ) for NBR (Fig. 1a) increase slightly at higher filler amounts. It is known that tan δ peak corresponds to the glass transition temperature (Tg) of the composites. The figure shows that NBR has a Tg at about −30 °C, while NR has a Tg at about −40 °C. In both cases the filler concentration has no impact on vulcanizates Tg and higher filler amounts reduce the peak’s intensity of mechanical loss angle tangent (tan δ). This reduced intensity results from: (1) the decrease of the number of mobile units participating the relaxation process and (2) the decrease of the magnitude of the modulus drop associated with Tg. As seen from the figure the peak’s intensity of mechanical loss angle tangent (tan δ) for NR (Fig. 2b) vulcanizates is higher than that of NBR (Fig. 2a) ones. The changes in the values for mechanical loss angle tangent (tan δ) for NR and NBR based composites filled with conductive carbon black are utterly due to the different chemical nature of the elastomers studied. In the case of crystallizing NR (Fig. 2b) where the filler has a lesser reinforcing effect the peak’s intensity of mechanical loss angle tangent (tan δ) is reduced less than in the case of no-crystallizing NBR (Fig. 2a) [32]. On the other hand, the higher polarity of NBR matrix predetermines stronger filler-matrix interactions. The lower mechanical loss angle tangent (tan δ) confirms the said interaction to be stronger in than in the case of non-polar NR. As said

Page 6 of 8 Fig. 4 Dielectric permittivity (ε′) dependence on the filler amount and frequency for the composites on the basis of (a) NBR and (b) NR at 100 °C

J Polym Res (2012) 19:16

previously, tan δ is a measure of the energy dissipation in the material and also is an indicator of the viscoelasticity of the sample [1]. The results have shown that in the case of NR and vulcanizates based on it the high elasticity and energy dissipation are greater than those in the case of NBR and its vulcanizates. Dielectric thermal analysis (DETA) of the composites Figure 3 presents the dependence of dielectric permittivity (ε′) on filler amount and frequency at 30 °C for NBR (Fig. 3a) and NR (Fig. 3b) composites studied. As Fig. 3a shows in the case of NBR the increase in the filler amount leads to an increase in the dielectric permittivity (ε′) values at all frequencies studied. The frequency alternations in the cases of the unfilled NBR (Fig. 3a) based vulcanizates and of vulcanizates filled at low amounts of Printex L6 carbon black (up to 20 phr) have no considerable effect upon the dielectric permittivity (ε′) values which are determined by the elastomer matrix. At filler concentration over 20 phr dielectric permittivity (ε′) values decrease with the increasing frequency which is most pronounced at the highest filler concentrations. Regardless of the fact that there is not any drastic change in the dielectric properties that reveals reaching and passing the percolation threshold, the frequency dependence of ε′ in the case of vulcanizates filled at 30 phr (Fig. 3a) evidences that concentration to be the critical one for the occurrence of
Fig. 5 Dielectric loss angle tangent (DETA tan δ) dependence on the filler amount and frequency for the composites on the basis of (a) NBR and (b) NR at 30 °C

electrically conductive pathways enabling the polarization of the system. No difference in dielectric permittivity (ε′) values as a function of frequency studied is observed only for NR (Fig. 3b) composites (unfilled and filled at 10 phr). At higher filler concentrations, as it is in the case of NBR composites, the increasing frequency leads to a decrease of dielectric permittivity (ε′) values for NR composites, too. However, in the latter case the drastic change in the dielectric properties of the composites is at a lower filler concentration – at about 20 phr. That means the percolation threshold for NR composites is reached at filler concentrations lower than those for NBR ones, i.e. the effect of the introduced conductive carbon black is more pronounced. That might be explained by the NR crystallizability and higher specific volume resistivity. The latter parameter is more affected by the introduction of conductive filler. That effect is not that marked in the case of NBR which principally has a significantly lower specific volume resistivity. Probably the more ordered NR structure allows the occurrence of electrically conductive pathways at lower filler concentrations. As Fig. 3b shows, the increase in filler amount in NR composites does not cause significant changes in their dielectric properties when the percolation threshold is passed. Moreover, at high frequencies (100 kHz and 1 MHz) no changes are observed in the dielectric permittivity (ε′) values for filler concentrations higher than 30 phr.

J Polym Res (2012) 19:16 Fig. 6 Dielectric loss angle tangent (DETA tan δ) dependence on the filler amount and frequency for the composites on the basis of (a) NBR and (b) NR at 100 °C

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The dependences of dielectric permittivity (ε′) on filler amount and frequency at 100 °C for NBR and NR composites studied are presented in Fig. 4. The figure shows that at 100 °C the tendency of the changes in dielectric permittivity (ε′) observed at 30 °C to be the same. However, in the case of both elastomers dielectric permittivity (ε′) increases significantly with the raising temperature. At low frequencies (1 kHz) there are differences in the dielectric permittivity (ε′) values for NBR (Fig. 4a) composites at 100 °C. Those differences exist at low filler concentrations as well as for unfilled vulcanizates and for the ones filled with low amounts of Printex L6 carbon black. Such a change in the dielectric properties of the studied NBR vulcanizates is not observed at 30 °C and is likely due to the availability of a nitrile group in that elastomer. Possibly at low frequencies and higher temperatures the nitrile group causes a partial polarization of the rubber matrix. One should also take into account the fact that at 100 °C NR (Fig. 4b) is completely decrystallized what also affects the formation of electrically conductive pathways and its dielectric properties. The dependences of dielectric loss tangent angle (DETA tan δ) on filler amount and frequency at 30 °C for NBR and NR composites studied are presented in Fig. 5. As mentioned above, no significant changes are observed in dielectric permittivity (ε′) values. However, DETA tan δ values for both elastomers are dependent on the frequency at which the experiments were run, regardless of the filler amount. The dependence is more pronounced for the NR vulcanizates.
Table 4 Specific characteristics of raw non-vulcanized NR and NBR [28] Property Density, g/cm3 Dielectric permittivity at frequency of 1000 Hz 3) Dielectric loss tangent 4) Volume resistivity, Ω.m 5) Glass transition temperature, °C NBR 0.962 10.20 0.3100 3.107 −30 NR 0.915 2.55 0.0016 5.1012 −70

The filler amount affects the said parameter in the case of both elastomers. At low frequencies (1 kHz) the vulcanizates comprising Printex L6 carbon black at 50 phr have the highest DETA tan δ values which decrease with the increasing frequency. Figure 6 plotting the dependencies at 100 °C show higher DETA tan δ values. Nevertheless, the increasing frequency causes a decrease of DETA tan δ values for NBR vulcanizates regardless of the filler amount. The same results were obtained for NR vulcanizates. The only dissimilarity is that there is no visible difference in DETA tan δ values as a function of frequency for the unfilled composites and for those filled at 10 phr. Probably the different polarity and proneness to crystallization of the two matrices, as well as to the molecules mobility and to intermolecular interaction forces in each matrix determine the changes in DETA tan δ values for NR and NBR composites studied comprising different amounts of conductive carbon black. The two matrices used may be characterized as follows: A comparison of some of NR and NBR specific characteristics presented in Table 4 reveal the nature of the effects those matrixes have on the properties of the composites studied: As Table 4 shows the two elastomer matrices have very different properties and parameters which under the same all other conditions are the main reason for the different dielectric mechanical and dielectric behaviour of the composites based on them. Hence, the choice of matrix depends on the targeted properties of the composites and their particular applications.

Conclusions The study presents the effect that two elastomeric matrices different in their chemical nature (a non-polar and crystallizing natural rubber and a polar and non-crystallizing acrylonitrile-butadiene rubber) have upon the dynamic mechanical and dielectric properties of the composites comprising different amounts of conductive carbon black. Moreover,

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J Polym Res (2012) 19:16 11. Heinrich G, Klüppel M (2002) Recent advances in the theory of filler networking in elastomers. Adv Polym Sci 160:1–44 12. Thomas S, Stephen R (eds) (2010) Rubber nanocomposites. Wiley, Singapore 13. Angellier H, Molina-Boisseau S, Dufresne A (2005) Mechanical properties of waxy maize starch nanocrystal reinforced natural rubber. Macromolecules 38:9161–9170 14. Gatos KG, Sawanis NS, Apostolov AA, Thomann R, KargerKocsis J (2004) Nanocomposite formation in Hydrogenated Nitrile Rubber (HNBR)/Organo-Montmorillonite as a function of the intercalant type. Macromol Mater Eng 289:1079–1086 15. Wang Y, Zhang H, Wu Y, Yang J, Zhang L (2005) Preparation and properties of natural rubber/rectorite nanocomposites. Eur Polym J 41:2776–2783 16. Kalgaonkar RA, Jog JP (2008) Molecular dynamics of copolyester/clay nanocomposites as investigated by viscoelastic and dielectric analysis. J Polym Sci Part B Polym Phys 46:2539–2555 17. Rao YQ, Pochan JM (2007) Mechanics of polymer-clay nanocomposites. Macromolecules 40:290–299 18. Hernandez MC, Suarez N, Martinez LA, Fejoo JL, Monaco SL, Salazar N (2008) Effects of nanoscale dispersion in the dielectric properties of poly(vinyl alcohol)-bentonite nanocomposites. Phys Rev E77:051801 19. Page KA, Adachi K (2006) Dielectric relaxation in montmorillonite/polymer nanocomposites. Polymer 47:6406–6410 20. Psarras GC, Gatos KG, Karger-Kocsis J (2007) Dielectric properties of layered silicate-reinforced natural and polyurethane rubber nanocomposites. J Appl Polym Sci 106:1405–1411 21. Wan NY, Chin KP, Saad CS (2010) Comparison of epoxidised natural rubber (enr) 37.5 and enr 25/enr 50 physical blend: specialty polymer for “green tyre” application. IOP Conf Ser: Mater Sci Eng 11:012004 22. Small W, Wilson TS (2010) Crystallization behavior of virgin TR55 silicone rubber measured using dynamic mechanical thermal analysis with liquid nitrogen cooling, Lawrence Livermore National Laboratory, LLNL-TR-426277 23. Ghadir M, Zimonyi E, Nagy J (1994) Thermal investigation of silicone rubber containing imide-siloxane copolymers. Thermal Anal Calorimetry 41:1019–1029 24. Pandey AK, Setua DK (2006) Raw material and applications– study of damping behavior of rubber- plastic blend. Kautsch Gummi Kunstst 59:45–4 25. Boye WM, Terrill E (2011) Structure–property analysis of unfilled polyisoprene (IR) vulcanizates characterized by mechanical and rheological measurements, Rubber World, Aug. 22–27 26. Niedermeier CW Carbon blacks for electrically conductive rubber products, Evonik (Degussa), Technical report TR 812 27. Gozdiff M (2001) Acrylonitrile-butadiene rubber. In: Dick JS (ed) Rubber technology: compounding and testing for performance, 1st edn. Hanser Publishers, Munich, pp 193–201 28. Kornev A (2005) Technology of elastomeric materials, Istek, Moscow, (in Russian) 29. Dick JS (ed) (2001) Rubber technology, Hamser, Munich 30. Varghese S, Karger-Kocsis J, Gatos KG (2003) Melt compounded epoxidized natural rubber/layered silicate nanocomposites: structure-properties relationships. Polymer 44:3977–3983 31. Ramier J, Gauthier C, Chazeau L, Stelandre L, Guy L (2007) Payne effect in silica-filled styrene–butadiene rubber: influence of surface treatment. J Polym Sci Part B: Polym Phys 45:286–298 32. Wolf S, Wang M (1993) Carbon black reinforcements of the elastomers, In Carbon black, 2nd Edition, Marcel Dekker, New York

the matrices differ in some of their chief characteristics (dielectric permittivity, DETA tan δ, specific volume resistivity, Tg). The experimental results show that the matrices studied and their specific properties have a great impact upon both the dynamic mechanical and dielectric parameters of the composites based on them. The chemical nature, structure and specific characteristics of the matrix affect the storage modulus, glass transition temperature, elasticity behavior, highelasticity, energy dispersion, dielectric permittivity and DETA tan δ of the composites investigated. The matrix effect dominates at lower filler amounts and determines the properties of the composites. The introduction of a filler and its increasing amount choke that effect, so the composites characteristics become less dependent on the specifics of the matrix. However, some of the composite properties (elasticity behavior, high-elasticity, energy dispersion, dielectric permittivity) are predetermined by the elastomer even at a considerable filler amount. Hence, the choice of an elastomer matrix is of crucial importance for tailoring the properties of the composites.
Acknowledgments The present research is a result of an international collaboration program between University of Tabuk, Tabuk, Kingdom of Saudi Arabia and the University of Chemical Technology and Metallurgy, Sofia, Bulgaria. The authors gratefully acknowledge the financial support from the University of Tabuk.

References
1. Shaw M, MacKnight W (2005) Introduction to polymer viscoelasticity. Wiley, New York 2. Lobo H, Bonilla H (eds.) (2003) Handbook of polymer analyses, Dekker 3. Dang Z-M, Song H-T, Lin Y-Q, Ma L-J (2009) High and low dielectric permittivity polymer-based nanobybrid dielectric films. J Phys Conf Ser 152:012047 4. Gabbott P (ed) (2008) Principles and application of thermal analyses. Blackwell Publishing, Oxford 5. Ferry JD (1980) Viscoelastic properties of polymers. Wiley, New York 6. Heinrich G (2011) advanced rubber composites (Advances in Polymer Science, 239). Springer, Heidelberg 7. Fritzsche J, Das A, Jurk R, Stöckelhuber KW, Heinrich G, Klüppel M (2008) Relaxation dynamics of carboxylated nitrile rubber filled with organomodified nanoclay. Express Polym Lett 2:373–377 8. Das A, Costa FR, Wagenknecht U, Heinrich G (2008) Nanocomposites based on chloroprene rubber: Effect of chemical nature and organic modification of nanoclay on the vulcavizate properties. Eur Polym J 44:3456–3465 9. Das A, Jurk R, Stöckelhuber KW, Engelhardt T, Fritzsche J, Klüppel M, Heinrich G (2008) Nanoalloy based on clays: intercalated-exfoliated layered silicate in high performance elastomer. J Macromol Sci Chem 45:144–150 10. Eisenberg A, Hird B, Moore RB (1990) A new multiplet-cluster model for the morphology of random ionomers. Macromolecules 23:4098–4107